Friday, December 8, 2023


Have you “tested” your TPMS?

RV Tire Safety

with RV tire expert Roger Marble

Like anything mechanical or electrical, TPMS parts can die, wear out or malfunction. While I am not aware of a lot of reports of failures of tire pressure monitors or sensors (TPMS), I would be surprised if the only problems were related to battery life or improper setup.

This post is limited to TPMS that use externally mounted sensors, i.e., the ones that screw onto the end of your valve stem.

Batteries: They eventually will die. The early warning of low battery power from a sensor that previously was working appears to be an occasional intermittent loss of signal, followed eventually by almost constant no signal on the display. This is easy to fix as most of these systems have user-replaceable batteries. I always carry a couple, but I don’t stock up as batteries may lose power even sitting in their original packaging.

O-ring: Under the screw-on plastic cap there is a very small O ring. As with any rubber component they can simply die (crack or tear) from normal use as rubber does “age out” due to exposure to heat and ozone in the atmosphere. I would suggest having a few O-rings on hand as, unlike the batteries, you can’t just pick up a replacement at CVS, Walmart or Walgreens. You will probably have to get them from your TPMS dealer. When you screw the cap on the sensor don’t over-tighten the cap as that can distort the O-ring and shorten its life

Plastic cap: This part should last longer than the rubber O-ring, but plastic ages too. Again this is special and unique to your brand TPMS, so having at least one on hand from your dealer is a good idea. Also, don’t over-tighten the cap. It might be possible to seal a cracked cap for a short time with silicone seal or glue, but be careful not to glue the cap to the sensor.

Sensor electronics: All you can do here is get a new replacement sensor. Some brands of TPMSs offer a longer-term warranty (lifetime), others only 12 months. I do carry a spare sensor but not in my toolbox or parts box, but I added a sensor to my spare tire in my Class C. This gives give me a replacement I could use on a ground tire if one of those sensors ever failed. It would only require a quick program change when I move the sensor from a spare position to the ground tire. I could do without a sensor on the spare for the week it might take to get a replacement sensor.

The reputable dealers I have talked with all offer single sensor sales or replacement under warranty. A sensor on a spare tire would probably last longer than the other external sensors as it isn’t exposed to potential strike from road debris or heat from the tire or brake drum. If I had a sensor fail I would plan on keeping the cap and O ring, if in good condition, as a future spare part.

Monitor: Well, if this part fails I don’t know of any repair a user could do. You just need to get a new monitor from your dealer and hope you have a good warranty and that your dealer will sell the monitor by itself so you don’t have to buy another complete system.  I have to admit that I did manage to damage my older monitor after four years of reliable use. I grabbed the wrong power cord and connected it to a 12V source, which fried the monitor that only wanted 5V. My bad. Luckily I was able to get just the monitor and didn’t have to buy a bunch of new sensors at the same time.

Replacement parts: If you bought your TPMS from a dealer that specializes in the RV market and attends RV shows, then you should be able to get individual parts with little problem. If, on the other hand, you purchased mail order from Amazon or eBay or someplace similar, I have no idea what parts or service you can expect.

Testing:  This is something I doubt any have done, but after some consideration, I think I have an easy and workable plan.

I suggest at least once every 6 months when you are at a location where you have nice weather and a bit of time you conduct an operation test.

With the system on, I would record all the readings for both pressure and temperature. With the co-pilot in the driver seat, I would go to each tire position and unscrew the sensor. The co-pilot should signal the tester as soon as a warning is given on the monitor. You might use your phone or walkie-talkie or maybe a third person, as honking the horn as a signal might become bothersome for your neighbors.

If all the sensors give a warning within a few seconds (read your manual on the claimed warning time), all is OK. If there is a delay or no warning after, say, 10 seconds, then there may be a problem in either the sensor or monitor or programming. In that case, you MUST learn the “why” and take corrective action, as you are depending on receiving prompt warning of air loss.

You can also use this opportunity to confirm your cold tire pressure with your calibrated hand gauge. (See THIS post on how to confirm your gauge is sufficiently accurate.) You can also “top off” your cold pressure with your normal margin of air.


Read more from Roger Marble on his blog at



Roger Marble
Roger Marble
Retired Tire Design and Forensic Engineer w/50+ years of experience. Currently has Class-C RV. Previous Truck Camper, Winny Brave, Class-C & 23'TT. Also towed race car w/ 23' open trailer and in 26' Closed trailer. While racing he set lap records at 6 different tracks racing from Lime Rock CT to Riverside CA and Daytona to Mosport Canada. Gives RV and Genealogy Seminars for FMCA across the USA. Taught vehicle handling to local Police Depts



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Larry (@guest_50050)
4 years ago

Roger, why not just take the monitor with you to each tire. Then you don’t need that second person. I do like your practice of keeping a replacement sensor on the spare tire. Excellent idea.

Phil Smith (@guest_46457)
4 years ago

I have been having problems with air leaking out of tires, and it seems to be related to the TPMS sensors only. When I take the sensors off, the tires hold air just fine, and the tests at the tire shop shows no leaks from the tires. My TPMS is less than a year old, and I have only ever finger-tightened the sensors, but perhaps I am using too much force to tighten them. I’ve just always been concerned that when the sensor depresses the schrader valve on the tire, I’d better have an excellent (a.k.a. TIGHT) seal to the sensor. Time to try again…. or else I am going to internal sensors.

Thanks for the info!

Roger Marble (@guest_47266)
4 years ago
Reply to  Phil Smith

Try a spray of Windex or some similar household cleaner to learn where the leak is coming from. RE tight I suggest tight till air leak stops then about 1/2 turn more.

Wolfe (@guest_46035)
4 years ago

Great write up and spare parts advice, Roger.

Your testing is almost exactly what I did on my TPMS when I first installed it, because i was concerned (without a booster) how reliable the transmission range was. I installed a sensor on my spare tire, pressurized and reset the alarm, and unscrewed the sensor. Rolled tire 5 feet behind the trailer, repeat. 10, 15, 20… I happily found I was safely within maximum reception during usage.

As for your voltage mishap, i’m surprised you don’t have a solar unit these days? Totally cordless for life, no power switch needed. Mine can recharge by USB if needed, but so far has no problem keeping up.

Roger Marble (@guest_47267)
4 years ago
Reply to  Wolfe

Thanks for the comment. Re voltage. Even with Solar, you need to use the correct adapter to get the correct voltage for whatever you are trying to charge.

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