Schrader valves or my TPMS is not working

I have a TST tire pressure monitoring system. The drivers side duels have stopped reading. I called the company and they were willing to send two new ones even though they were out of warranty. They asked me to move the non working units to a different wheel and check again, I did and they did work. So that left the valve extenders or the schrader valve, I think. The valve extender holds air with the pressure sender removed and I can add and remove air. I am thinking that the valve are slightly bent or something because the pressure units work on other tires and the good senders don't work on the two back wheels. Could I have over tightened the pressure senders on the valve stem or is their something else going on. At 90 bucks I don't want to buy new extenders and find they do not fix the problem.
Help,
Jim

Jim, can you remove the extenders from those wheels and try attaching the senders directly to the valve stems?  Can the schrader valves be replaced within the extenders?

I had one wheel like that.  Not only would the Pressure Pro sensor read, even my dual foot tire gauge wouldn't get a reading.  Turned out the extender Shrader valve was just a bit too short and my gauge and the sensor couldn't depress it.  A new extender fixed that.  In your case, since the did work once, I would try unscrewing the Shrader valves about a half turn.

My Pressure Pro used to have a problem like that with the left rear tire on my 5th wheel. When I contacted them they were very good about helping me. I learned that it's an RF signal from the sender to the antenna. So if it doesn't have a straight line path it has to bounce to get there, like off of another car, guard rail, truck etc. Moving the display helped if I put it higher. Also I found my Garmin GPS would interfear with it if it got too close, within about 8". They also told me the newer monitor's were less sensitive to weak signals so I ordered one because it had some more features also. I tried other sensors in that position and they all worked the same.

Lou,
I will try this weekend to connect to the Tire stem, however, not sure I can even reach the inner tire. I located a schrader valve stem, truck repair place sold it to me for a buck. Will try that also. Then I will try Ned suggestion to just back out the valve, hoping it won't let air out.
Jim

Jim, when the sensor is installed, it keeps the Shrader valve open so it can read the pressure so backing out the valve should not cause any additional air loss.

Hi,
I think you'll find that extenders are often a problem. My major problem was that the sensor on the end of an extender tore the valve stem out when the clamp to the rim came loose (16" rim). I also had one that wouldn't read thru the extender, but was fine on the stem. I've found that I can install senders on all of the wheels (now 19.5") with just short steel valve stems and I do that despite the PIA.
Ernie

Ned said:

Jim, when the sensor is installed, it keeps the Shrader valve open so it can read the pressure so backing out the valve should not cause any additional air loss.

Click to expand...

If the Shrader valve is unscrewed slightly will it leak much anytime the sensor is removed to add air or double check pressure with an air gauge.

I may have the same problem with a steel truck extender.  When the tire shop installed my new tires last April they used new valve stems and  two new extenders for the inside duals.  No problem till I tried to add a few extra pounds of air for the first time while in Colorado last month due to much lower air temperatures lowering the tire air pressures.  Five of the tires took less than 10 seconds each to add 5-6 lbs but it took me almost 10 minutes for the one inside dual (fingers would get tired holding the air chuck tightly on the valve stem).  Even though the old extenders are a couple inches shorter than the new ones I was able to put one of the old extenders on and everything worked fine.  The tire shop must have used different length valve stems so they had to use longer extenders.  I'm going to take the offending extender back to the tire shop and see what they have to say before I start messing with the valve core.  If they furnish a new extender so much the better.

Allen

I meant that as a temporary attempt to determine if it's a short valve that's causing the problem.  If so, then you can replace it with a slightly longer one.  In our case, the difference in length was no more than 1/32".

Update,
I first attempted to remove the chrome hub cap and remove the extender and connect to the valve stem as Lou suggested. Took the tool supplied and attempted to remove the nuts with the slot as the instructions directed. No luck the tire shop must have put them on with a impact wrench. Moved on to Ned's suggestion. I had a valve stem removal tool backed out the first outside tire until I heard a slight air flow, installed the sender and went into the RV and waited for the system to cycle, yup pressure. On to the inner tire slowly backed out the valve stem no air leaking, holy smoke the valve is almost out and no air. Backed it all the way out the tire is flat or the inner stem is stuck closed. Got my high pressure air compressor out, I will show that tire who is boss. Put air into the tire for about five minutes no pressure, Dam. wonder if the gage is bad remove the sender from the outer tire and connected to the tire gauge is fine 105 on the nose.
Gave up called Good Sam will post a separate post on that hole experience. For this post guy came and we worked together he jacked the RV and I held the air hose and he wiggled the tire until the bead caught and we filled the tire. He checked everything and no leaks, by this time I am upset and worried. I have new tires maybe 70 miles and the tire might have been flat from the RV dealer or just gone flat when I drove around for propane. I just don't know.
Back to the tire pressure sender. While waiting for the service truck I installed the two pressure senders on my bicycle to make sure they transmit. The sender that was in the inner did not outer one did. I went to remove the senders and the front bike tire is flat, now that cannot be a cowincidence yikes Looks like the sender leaks. Will soap test it today. By the time the tire was repaired it was 7 PM and dark. So now I will take this to a truck repair shop to get the hub caps loose and replace or eliminate the extenders. I just don't want flats as part of my life.
Thank goodness all this happened in the RV park and not on the road. More to follow, sadly.
Thank all of you for giving me a track to follow, had I just assumed the tire being new had air I would have been in a world of hurt.
Jim