Windows Updates and Reducing Data Usage, Especially with Multiple Devices

Let’s face it–most full-time RVs have more than one electronic device running Windows.  While there are certainly some that stick to Apple (pricey) or Linux operating systems (free!), this post will hopefully be useful to the rest of you.

With truly unlimited and unthrottled data connections a precious commodity, and campground wireless typically no better than it was 10 years ago, most of us aren’t helping things by letting Windows download updates on each of our devices.  Simply put, if you have more than one device, you’re using twice what you need to in order to keep things up-to-date.

Even checking for updates, which your computer most likely does once a week, uses somewhere in the neighborhood of 200MB.  To put that in perspective, if you were to have two laptops, checking once a week (1.7GB), with 2 phones on Verizon’s 12GB+2GB/line plan for $120/month, your update checking is costing you about $13/month, plus taxes, if you exactly use your data allotment.  But there’s a way to reduce that, especially in the long run.  How is that possible without foregoing important updates?

Continue reading “Windows Updates and Reducing Data Usage, Especially with Multiple Devices” »

Line Splitter to go with Clamp-On Meter

Last time, I forgot to mention one thing you’ll want to have to go with the clamp-on meter–a line splitter for plugging in to standard 15-amp outlets.

What does this do?  It breaks out the line wire to where you can clamp around it by itself.  Without getting too far into the details, the clamp-on ammeter is going to show you net current through the clamp-.  If you just clamp it around a power cord, it will read zero–the black line lead and the white neutral lead complete a circuit, and current travels in opposite directions on those two wires.  To measure what you’re really after, you want just one of those leads in the clamp.

A line splitter makes getting just one lead in the clamp a plug-in operation. It also has one loop that is multiplied 10 times–which can be useful when you’re trying to measure smaller currents.  Another $15 gets you one of these to keep with your meter.

My New Favorite Multimeter, and Measuring Inverter and Charging Efficiency

A little while back, I posted a short writeup on a plug-in ammeter I’ve used to measure current on circuits with standard ATO blade-style fuses.  When running through trying to find out which circuits have loads on them, it’s still as easy as it gets, especially when you don’t have good access to the wiring.

Before I go any further, let me point out that I have a degree in electrical engineering.  If you’ve done any reading at all on here, you know that I mess with electrical stuff more than any sane person should.  My “needs” in the tool department are more extensive than most, but I’m going to talk today about a tool that’s affordable and useful enough that every RVer should carry one.

What is that tool?  A multimeter, but not just any multimeter.  There’s a lot out there to choose from, varying in price from very cheap (~$10) to very expensive (>$500).  If you walk in to your local hardware store, Sears, or Wal-Mart even, you’ll be able to lay your hands on a digital multimeter that will do quite a bit for around $10.  Something that will look kind of like this (pictures link to Amazon listings):

Cheap $10 Multimeter

It’ll read AC and DC voltage, DC current, resistance, and a few other things.  But I know that dial and the three connections can be a scary sight.  You have to set the right scale for whatever you’re measuring, and you have to know which hole the red lead goes into (if you pick up the meter to measure voltage and are connected to the 10A current spot, bad things will happen).  They do work just fine for a lot of things though–in a pinch, they’re quite useful, but require a little more care than some of the others I’ll talk about.

I strongly suggest getting an auto-ranging multimeter though.  It’s simpler to use, with a lot fewer settings on the dial to do the same measurements.  If you go to Lowes or Home Depot, you can spend less than $50 and get one like this:

Extech MN16A Auto-Ranging Multimeter

Now, instead of selecting a range for voltage measurements, the meter will do it for you.  This one will also measure frequency and capacitance–the former useful in checking out your inverter, the latter lets you check the capacitors on your air conditioners.  With a type-K thermocouple instead of the test leads, you can measure temperature, and when testing for continuity, it has an audible feedback so both hands can be used to hold (and watch) test leads.

Ok, so that’s better.  But that only lets us measure current where we can wire the leads inline with the circuit, only up to 10A, and for a maximum of 30 seconds (these specs are almost universal in this type of meter).  We know that we have RVs with 50A hookups, DC circuits with lots of fuses bigger than 10A, and that we don’t always want to be unwiring stuff to connect the meter inline.

The type of meter that makes that a lot easier is a clamp on meter.  Most of the ones you’ll come across will only measure AC current, not DC current.  That’s still useful, and I’ve had one like that for quite a while.  Clamp-on meters that could measure DC current were usually cost prohibitive–take this Fluke meter at nearly $300.  Is is a really nice meter? Sure.  Is it overkill for most RVers? Yep.

That’s not what I want either, even as often as I use one.  It’ll eventually get left out in the rain, loaned out, lost, etc.  Every crook knows what Fluke’s yellow color means in terms of value.  I don’t need a NIST calibration certificate, and it’ll be pretty rare that I need to measure more than 100A.

So instead of any of the above meters, what would I recommend?  This guy:

Uni-T UT210E Clamp-On True RMS AC DC Meter with Capacitance Tester

For less than $40 (click on picture for Amazon listing), this meter does essentially everything that the previously discussed meters will do.  It’s true RMS, which means you can get an accurate reading when you’re using a modified sine wave inverter.  Lesser meters will just measure peak voltage and divide by the square root of two to estimate RMS voltage (which is what the 120V measurement is–peak voltage is normally 170V).  It’ll measure AC and DC current with the clamp, along with AC and DC voltage, resistance, capacitance, diodes, and even has a built-in non-contact voltage sensor.  What’s that?  It’s a mode where the meter will beep faster as it’s moved closer to a live wire–a good confirmation check as you get ready to start to work on something.

Red lead with protective sleeve on, black with it removed.
Red lead with protective sleeve on, black with it removed.

I also like that the leads come with a removable plastic sleeve, such that only the very tip is exposed with it on.  When I’m reaching in to measure cell voltages on lithium batteries, for example, I would normally have to be extra careful to make sure my leads didn’t touch each other.  Like the Fluke meter, the display has a backlight, so I can read it in all of those RV nooks and crannies that would otherwise shadow my meter.

With just this one tool, I can learn a lot about the efficiency of my charging setup and inverter.  This post is already quite long, so I’m going to just preview for now what will be a more in-depth discussion in a few days.

Measuring current into the batteries, mostly charged, I can see what it takes to essentially “float” the batteries at a given voltage.  This is only about 37mA per kW of usable battery capacity, or about 23W for the full Volt bank.  On the old 12V house batteries, that was more like 60W, and keep in mind that was about 1/4 the capacity.  Big difference.

Measuring DC current into the inverter and AC current out, I can also measure voltages and figure out an effective inverter efficiency.  With a few things on, like a couple of TVs, computer, Xbox, kitchen lights (which are AC), and a number of little items I don’t really keep track of, the inverter was putting out about 2.17A at 120V, or about 260W.  On the DC side, at 48V, it was taking in about 6A or 288W.  If we divide the output wattage by the input wattage, we can figure the inverter’s efficiency, which comes out to 90%.  Now, after I ran around turning stuff off, the input wattage didn’t really change much–I’m not really much above the idle consumption for the inverter.

The charger draws about 175W with almost no load, and at full load is about 80% efficient–actually better than I expected.  But how does that compare to my old 12V setup?  The 12V charger generally maintained about a 400W draw when I wasn’t using anything on the DC system.  Remember it’s putting in about 5 amps just to maintain the batteries at their current state of charge.  I haven’t taken the measurements yet, but I’m willing to bet that charging a fully discharged Volt battery is quite a bit more efficient than similarly charging a lead acid battery. Don’t worry though–I’ll do the test and collect the data!

Next time, when I talk more in-depth about system efficiencies, I’ll also include pictures and video of the measurement process.  Whether your intentions are to check a campground pedestal, figure out what’s causing a battery to go dead, or something more sophisticated, I’m going to present a series of troubleshooting walk-throughs to help a non-EE safely figure out the basics of what’s going on before deciding whether to hire some help or buy your neighbor some beer.

Next: Line Splitter to go with Clamp-On Meter

Having a Little Fun with Lithium Batteries

This amounts to a bit of a side project, but provides a platform for really testing what the Volt lithium ion batteries are capable of.  You can tell by the image above that I’m talking about putting lithium ion batteries, from a Chevy Volt, into a golf cart.

Why not just replace the lead acid batteries?

There are several reasons.  The first is replacement cost–while this is a proof-of-concept, it can be done for about the same hardware cost as putting lead acid batteries in.  These carts typically have 6  6 or 8-volt batteries (depending on whether it’s a 36V or 48V cart).  Typical cost to replace the batteries is between $600 and $800.  The Volt batteries, while used, can be had for about $100 per usable kWh.  If we look at the lead acid batteries’ energy capacity to 50% depth of discharge, the standard configuration would be 3kWh of usable energy, or $200 per usable kWh.  A single 2kWh Volt module is already 48V, so we could run on just one, at a cost of $250.  But the goal is to make the electric carts go farther without charging on a golf cart, so we’ll install more than that.

Reason #2: Capital Cost and Replacement Frequency

Actually, the second reason is cost as well.  But from a different standpoint.  Typical lead acid batteries used on a golf course are only good for about 2 years.  If you assumed year-round golf weather and no rainy days, that would be a little over 700 discharge cycles.  The Volt battery should be capable of well more than that, and with proper management should be able to last 10 years or more.  In most cases, that will mean that the batteries will get moved to a new cart when the rest of the cart has reached the end of its life.

In addition to faster charging, we also have the ability to increase the amount of energy on-board, making charging stops less frequent.  Typically, on the course where the testing is going to happen, a cart is done for the day after two rounds of 18 holes.  How much energy is that?  We sent a cart out with a regular golfer with a monitor attached.  After 9 holes, the cart had used about 0.65kWh, or 2.6kWh after 36 holes.  That’s in keeping with the 3kWh expected of a new set of batteries.  It also means that with 3.6kWh of lithium capacity, it’ll be an improvement over the status quo.

Energy Monitor after 9 holes on lead acid batteries.
Energy Monitor after 9 holes on lead acid batteries.

But 3.6kWh doesn’t quite make 3 rounds of 18–it would only be about halfway through the back 9 on the third round.  We could install another module (bringing capacity to 5.4kWh and just over 4 18-hole rounds, for about $250 in batteries.  We could also install rooftop solar for about the same price, and extend the range of the 2-module configuration.  In two rounds, those panels should be able to pick up 1kWh pretty reliably most days, making for a solid 3 rounds.  Anything more, and they’re reducing charge time and cost.

Reason #3: Charging Cost

It might come as no surprise that the third reason is cost also–from a charging standpoint.  The lithium batteries should be more efficient in charging, and can do so much faster.  Faster charging means fewer charging stations are needed, and a cart might even be able to return for another round after a mid-day charge.  Getting an extra round out of a cart without an overnight charge means a course needs fewer carts, which of course saves money.

Now, with fewer carts, other things may wear out sooner (in time).  Carts get banged up on the course–whether it’s running rough in search of a lost ball, bumping into things, wear and tear from spikes on the floor mat or tees on the upholstery, they don’t last forever.  At least some of the mechanical wear is reduced though, as the cart is lighter than before.  Each 2kWh section is about 42lbs–so we’ll have 84 lbs of battery taking the place of almost 400.  That means that the cart ready to roll has shed 1/3 of its weight, not counting passengers and cargo, which should help the life of at least some of those components.

How easy is it to do?

Simply replacing the source of power is really easy. Take out all of the boat anchors, and connect the power leads to the 42lb module, and the cart will run.  In a Club Car DS with a separately excited motor and electronic controller, here’s the result:

Ok, so I was kind of cheating–with the electronic controller there’s a pre-defined ramp-up in power when you floor it.  I was holding the brake during the ramp period so that I got off the line quicker.  In an older Club Car cart, with a series motor and no electronics, it’s simply how fast you step on it that matters.

Getting a quick launch is actually a lot easier that way, but also becomes something that we don’t want out tearing up the course. Not everyone is going to practice a quick launch with a brake hold; it’s far more likely that someone will just stomp on the pedal.  More on that later.

One 2kWh Chevy Volt module sitting where 6 T105s used to live.

But it looks a little lonely without company.  To protect the pack from overcharging or over-discharging, we need a controller and new charging system.  That’s a little more sophisticated, as it’s something that doesn’t exist off-the-shelf.  But since we’re going to the trouble, there are a few other things that can be done at the same time:

  • Charge/discharge control–turn the charger on and off at the right times and disable the cart from moving if the battery is depleted.
  • Solar charging–control power from 240W of solar mounted on the roof going into the batteries.  Simply turn off controller at night to eliminate need for blocking diodes.
  • Temperature monitoring–detect problems, and prevent use in temperature extremes.
  • Data logging–this is a big one.  We hope to learn a lot about how these batteries really work.  With a fleet of carts, this should prove invaluable.
  • Simplified cell balance monitoring–we’re not going to automate balancing, but we will keep an eye on it.
  • Remote shutdown–should course staff see someone starting to do something they shouldn’t, the cart can be turned off remotely until someone goes out to address the problem in person.
  • Geofencing–carts aren’t allowed on the greens or on tee boxes.  Geofencing means that the cart can be disabled or sound an alarm if someone tries driving in one of these areas.
  • Anti-theft–should someone try to steal a cart, it will lose its connection to the course’s wireless network.  It’ll sound a Hollywood-style bomb countdown, then self-destruct.  No, not really (or maybe it will–don’t steal golf carts!) Seriously, it’ll be set to stop working if it can’t phone home for a couple of days–long enough that intermittent connection problems don’t interrupt play.

That all probably sounds complicated, but there’s a lot of overlap with the house battery system that’s been installed since February. The whole system should be ready for testing on the golf course within a week.  Here’s one more video, showing the cart tooling around with the solar panels working.

I’ll follow up on more of the controls, wiring, and the rest before long.

Wiring a US-spec Smart ForTwo (451) for Flat Towing

Ok, so this project isn’t something for my RV.  My parents have a small motorhome, and have occasionally towed a Saturn Vue behind it.  There’s a Smart Fortwo in the fleet now, and given that it weighs about half what they’re towing now, it makes sense to get the Smart all set up.

North American Smart Tail Light. Upper compartment is combined stop, tail, and turn light; bottom compartment is reverse and the rear reflex reflector.

Of course, I’m the resident EE and car guy in the family, and pretty particular about connecting wiring for towing as simply and smartly as possible, which means I get this job to do.  Normally the process is pretty simple–find a wiring diagram for the lighting circuits, find the wires for the functions I need, and then figure out the easiest (i.e. closest to the front of the car) place to tie in to them.

Non-US Smart Tail Lamps. Labels added to show individual compartment functions--note that upper part of lamp is subdivided into an upper stop lamp and lower amber turn signal.
Non-US Smart Tail Lamps. Labels added to show individual compartment functions–note that upper part of lamp is subdivided into an upper stop lamp and lower amber turn signal.

The Fortwo presents a little bit of a challenge though.  The best resource for information on this little car is the Evilution site, but the electrical information is for the non-North American version of the car.  One of the most prominent differences between the NA version and the rest is the use of combined stop and turn lights here.  Now, this makes connection to the motorhome simpler (the standard 7-pin RV plug is a combined stop/turn configuration), but the pin numbers and wire colors don’t match what’s readily available online.

Lamp access panel inside right cargo area.
Lamp access panel inside right cargo area.

Getting access to the tail lights is easy enough: there’s a plastic access panel on either side of the cargo area, and releasing a clip in the middle frees up the back of the housing where you can see the two bulbs, and–getting a little excited–an empty bulb holder with leads to the plug.


Looking into lamp compartment.
Looking into lamp compartment.
Back of lamp holder. Note clip in upper middle. Squeeze to release.
Back of lamp holder. Note clip in upper middle. Squeeze to release.
Bulb holder, removed. This appears to be identical to the non-US bulb holder--the differences are in the lamp housing, and wire harness connecting to it.
Bulb holder, removed. This appears to be identical to the non-US bulb holder–the differences are in the lamp housing, and wire harness connecting to it.

The excitement is killed pretty quickly though, as the lamp and reflector don’t have a hole for the extra bulb.

Signal Acquisition Module, or SAM.
Signal Acquisition Module, or SAM.

But we can see the wire colors, and then move up to the electrical nerve center of this car–the SAM, or Signal Acquisition Module.  It’s basically an I/O board that has a lot of inputs from switches on the car–turn signals, wipers, etc., and miniature relays of various types for controlling outputs.  It also incorporates the fuse box, which is visible below and behind the driver’s knee bolster.

We can remove the SAM and get access to the connectors on the back side by removing the two screws along the front edge.  Whether looking at the US or non-US wiring diagrams, the parking lights are the same (though they’re “standing lights” across the pond).  They’re a gray wire with a green stripe:


But things get a lot more interesting with the turn signals.  When a turn signal is activated on a non-US Smart, with a dedicated bulb in back, the front turn lamp, side repeater, and rear lamp can all be wired together–they’re all on or off under identical logic.  But on the US-spec Smart they’re combined with brake lights in the rear–which means they need to be connected to the brake light circuit when braking, but that signal needs to be replaced by the one from the turn signal when turning–i.e. the brake light signal needs to be disconnected from the light where the turn signal is active.  Complicating things a bit further is the requirement that those same lights show the brakes (i.e. solid lights) when the hazard flasher is active.

Just about every American car since the dawn of the automotive turn signal has accomplished this logic via a separate set of contacts for the rear lights in the turn signal switch.  But not this car.  Finding the brake/turn wires at the SAM, I connected power to test that I’d found the right ones.  But instead of lighting the rear light, I got the front and side lights.  I was just a little confused, and decided to go to the source: factory wiring diagrams at AlldataDIY.

Item descriptions. It would be a lot easier to follow the diagrams if they’d just put this information directly on there!
Left side stop/turn wiring
Right side stop/turn wiring

It took a little while to figure out what was going on.  There are two relays mounted near the SAM (along the edge toward the front of the car) that both the front and rear lights connect to.  When the turn signal switch is active, the relay for that side is energized, connecting the front flashing signal with the rear lamp, and interrupting the stop signal.  The control wire for the relay is grounded–the hot side is always powered.

I have to wonder why Smart didn’t just program the logic for the stop lamp–given that the SAM knows about the turn signal switch–to combine the brake/turn logic in software and drive the output for the rear lights accordingly.  That would have eliminated two relays and simplified the wiring a good bit.  I’m sure there was some good reason…

This configuration means that while front and rear turn signals have the same wire color, they’re only linked together when the turn signal is active.  Connect to the correct side of the relay though, and we get almost exactly what we’re after.  I was very tempted to use a DPDT relay and the 12V pin from the 7-pin plug to ground the control side of the relays so that the front and side turn signals would operate as well–it would have meant that I could have made all of the connections under the “hood”, but if the auxiliary power pin on the 7-pin connector wasn’t powered, the rear brake/turn lights wouldn’t work–I didn’t like that possibility.

The simplest way to make things work right was to connect the stop/turn wires from the 7-pin plug to the rear stop/turn lights at the relays under the dash.  That meant not fishing wire to the rear of the car, but did require getting through the firewall.  Can you call it a firewall when the engine is in back?

Here are the rest of the connections:

Green wire from 7-pin plug connects to black wire with green stripe, on pin 8 (not the same wire colors on pin 2), for the right rear stop and turn lamp.
Towing arms and 7-pin connector (unmounted) in lower grille opening.
7-pin plug wiring from the harness bought with the plug runs between the coolant and windshield wiper fluid reservoirs to the main harness grommet through the firewall.
Firewall grommet. Wires were passed through, then it was re-sealed.
Left stop/turn wire is connected to pin 8 on the other relay, which is a black wire with white stripe.
The ground stud on the left side of the driver’s footwell was an easy place to connect with a ring terminal.

After those connections were made, the plug was tested and everything works as planned.

Measuring Current on DC Circuits

On most RVs, there isn’t a nice wiring diagram with fusing, grounding and splice locations, wire colors, and printed circuit identifiers like we expect on a car.  When something isn’t working, it’s often not obvious what circuit it’s on; when a fuse blows, we often don’t know what’s on the circuit that might have caused it.

It’s also pretty common for fuses to be oversized, not so much for the wiring, but such that if a problem were to occur, a fuse isn’t going to be very quick to blow.  It’s not easy to work with a standard multimeter to connect inline, and measure the current with the load turned on.

Here’s what I use:

EXTECH Automotive 30A Current Tester
EXTECH Automotive 30A Current Tester


This is one of my favorite automotive electrical diagnostic tools beyond a multimeter.  It’s a really simple current meter that plugs in where the fuse goes, and the fuse plugs in to the side of the connector.  I can see that my water pump peaks at just under 5A, and the furnace at 10A.  Same thing for lighting circuits, the refrigerator, etc.  This also allows you to put together an estimate of what you need in terms of batteries, solar, generator runtime, etc. if you were to run something for a particular amount of time.

It’s not quite as sophisticated as the Kill-A-Watt meters used for 110V power, but does it’s job quite well.

The Grey Ghost’s New Kitchen, Part 6: Loose Ends

This has dragged on quite a while, and will probably continue to, but I thought it might make sense to post some comments on a number of smaller items so far in the project.  Some are just notes on how I’ve done certain things, others are thoughts on what I’m planning.  As always, comments and suggestions are appreciated!


I’ve been asked how I have finished the cabinets–both what I’ve used and how it was applied.  All of the wood used is a red oak–in the case of the wood used for the face frames and the plywood for the sides of the cabinets, it was purchased at Lowe’s.  The cabinet doors and drawer fronts are also red oak, but supplied by Barker Door in Oregon.

I used an orbital sander (like this) to progressively sand all surfaces, starting with 120 grit, then 220 grit.  Before a final pass with 320 grit, everything was wiped with a wet rag to raise the grain–this results in a smoother finish when stain is applied.

The stain used for these cabinets is Minwax’s Espresso.  I found it on the shelves at Home Depot, but it can also be found online for about the same price.  I tried their PolyShades all-in-one product, but wasn’t nearly as satisfied as with the separate stain and polyurethane.  The stain was applied with a foam brush, and after sitting for about five minutes wiped with a paper towel.  The stain doesn’t dry quickly–it needs a day or so before it’s ready for polyurethane.  This caused a little bit of trouble at one point trying to get staining done when the weather wasn’t cooperating.

The polyurethane goes on pretty easily, but you do have to be careful to make sure you don’t go too thick and get runs.  A couple of hours between coats is all that’s needed for this to dry.  To get a smooth finish, a very light rub with 000 steel wool between coats knocks down any bubbles/bumps.  For most parts of the project, I put on 3 coats of polyurethane.

Stove cover

This is one part of the project that took a lot more effort than I expected.  I wanted

Routing on underside of cover.

the stove cover to sit level with the countertop, and to fit over the grating so that it wasn’t inclined to slide around while driving.  That meant a lot of work routing out about 1″ across most of the underside of the cover.  This probably took several hours, but I’m happy with the result:

Cooktop cover in place.
Cooktop cover in place.

Ceiling trim

Haven’t quite figured out what I’m doing here.  I left myself enough room at the top of the cabinets to do a small soffit (mainly to cover some of the holes from the old cabinets), which I plan to add lighting to.  Just haven’t done it, and haven’t decided what I want it to look like.

I also need to figure out how to clean the ceiling.  It has a fine layer of what I think is diesel soot, and is a royal pain to get free.  I’ve gotten a few sections clean with a lot of work, which ends up making it worse by highlighting how dirty the rest of it is!


Looking forward into bathroom from bedroom, as it was when I bought it.
Looking forward into bathroom from bedroom, as it was when I bought it.

The floors were actually the first project, tied in with replacing the shower stall.  I used Allure Aspen Oak click-lock vinyl plank flooring, bought at Home Depot.  It’s more expensive than the laminate planks, but being solid vinyl is way more tolerant of moisture.  I’d had problems in the bathroom with the pressboard swelling from drips from the shower door and wet feet.

I didn’t take any pictures during the process, but here are a couple of pictures before and after in the bathroom.

Vinyl floors in bathroom and bedroom.
Vinyl floors in bathroom and bedroom.

These floors have held up really well, and I think they do a good job lightening things up and providing contrast with the darker cabinets.

That’s all for now, but hopefully the next few posts won’t take so long!



Belts, Tensioners, and Pulleys

Years ago, during a pre-purchase inspection before finalizing the deal to buy the Grey Ghost, the Volvo mechanic pointed out that both belt tensioners really needed to be replaced, but that it wasn’t urgent.  I put the project off for a while–amost a year–until after successfully starting the world’s first nuclear reactor using heat pipes and Stirling engines.  After doing that, replacing a pulley seemed like it should be pretty easy.

It was almost too easy.  Just a few minutes, in fact, working at eye level and without getting dirty.  Loosened the spring tension with a 1/2″ drive ratchet, slipped the belt off, and unscrewed one bolt with a 14mm socket and the pulley was free.  I knew the other tensioner needed to be replaced, but the Cummins dealer didn’t have one on the shelf, and I was only in town (Las Vegas) for the weekend.  There was also a little sticker shock–they wanted almost $300 for that little thing.  I figured the worst that could happen was the tensioner letting the belt slip, in which case I could cut the belt and forgo AC until I got somewhere to fix it–maybe uncomfortable, but not disabling.

Somewhere along the way, I did a little searching and came across a Gates cross reference for the Cummins part number.  There was a pretty big difference in price–that tensioner would only be $120.  So it got replaced in 2014.

Both tensioners have done their jobs just fine, but recently I started noticing a bearing squeal when it was wet outside.  Knowing the tensioners (and tensioner pulleys) were basically new, that really only left the idler pulleys, one for each belt.

With some really nice weather over the weekend, I decided it was time to take care of it.  Of course, I decided this after the Cummins dealer was closed, and unlike with the tensioners, I couldn’t make out a part number on the idlers.  A little searching turned up a number that crossed to a Gates part, one that wasn’t in stock at the NAPA distribution center that would normally be the go-to place.  On a whim, I called the closes O’Reilly’s–they had the part, for about $35.  I headed down there, and while they had the part I asked for, it wasn’t the one I needed.

The clerk tried to be helpful (I was playing this RockAuto commercial in my head…), asking what it went on.  When I said a Volvo truck, he started typing and I was shocked to see the VNL listed as a model just after the V70 and ahead of the XC90.  Really?  Ok, but I have a Cummins engine–sure enough, it was listed.  Along with all of the part numbers I needed for the idlers, tensioners, and belts.  And all of them were in stock locally.

I did shop around just a little–I wanted the idler for the fan belt right away, since it was already off–and found that I could do better on Amazon by a pretty good margin.  I picked up the idler for $90, and ordered the other idler and both belts.  Combined, I was able to save $75.

This is one of those projects that takes longer to write up than to actually do.  Start to finish was well less than an hour, and most of that was just fishing the fan belt between each of the fan blades and the fan shroud.

Tools needed:

  • 14 and 15mm sockets
  • 1/2″-drive ratchet with long handle or cheater bar
  • Pry bar or breaker bar

Parts needed (pictures linked):

  • Gates 38610 AC belt tensioner, $119.78
  • Cummins 3978022, $141.14, or Gates 38504 fan belt tensioner, $85.78
  • Gates K120842 or K120842HD Fan belt, $68.16
  • Gates K060637 or K060637HD AC belt, $18.79
  • Gates 36286 fan belt idler pulley, $67.85
  • Gates 36223 AC belt idler pulley, $39.45

I mentioned that I had replaced each of the tensioners separately, but given that most of the big trucks put into RV service already have quite a few miles, I’d probably recommend doing everything at once (the extra cost is in parts, not time).

The first thing to do is get the fan belt loose.  Stick the 1/2″-drive ratchet into the square hole on the tensioner and push up (clockwise) to relieve tension.  Slip the belt off of the idler pulley above the tensioner, and release the ratchet slowly.  You may need a pry bar to support the tensioner in place while you reposition the ratchet to fully release the tension.

Ratchet on fan belt tensioner, squeaky idler on top side of belt.

Do the same thing on the AC belt tensioner, except using a 15mm socket and prying counter-clockwise.  Again, slipping the belt free at the idler pulley is easiest.

Ratchet on AC belt tensioner. Idler to be replaced is just above ratchet head.

The AC belt is easily freed with the fan belt pulled off of the water pump, while the fan belt will have to be fished over the fan blades into the space between the fan and radiator in order to get free.

The pulleys are both held in with 14mm bolts–unscrew, swap out the pulleys, and re-tighten.  Install the new AC belt first, then fish the new fan belt into the space between fan and radiator, and over each fan blade before slipping it into place.  Same operation in reverse with both tensioners, though it may require a little more effort going back together–you’ll have a stiffer, newer belt, and stronger tensioners.

Done. New belts, tensioners, and idler pulleys.

A few things were learned here:

  • Like with cars, the dealer isn’t necessarily the cheapest place for parts.
  • Unlike with cars, most auto parts places can’t look up your truck’s make and model (though neither can the dealer…they tend to want to work from your VIN or ESN).  O’Reilly’s proved an exception here.
  • Despite being bigger, the ease of access and eye-level work area made it much easier than working on a typical passenger car.
  • At about 240,000 miles, both idler pulleys were well worn, but both belts were probably fine to leave in service.  Not too different from passenger cars in that regard.