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Topic: Losing Rear Air Pressure while traveling down grade (Read 481 times) previous topic - next topic

Losing Rear Air Pressure while traveling down grade

 About a month ago, while traveling (west on 80 toward Salt Lake),  my Silverleaf dash warning lights started flashing that I was "WARNING! LOSING REAR AIR." within 45 seconds, I had gone from 118 LBS of pressure to 45 lbs! The coach breaks did not lock-up, and after an intense few moments, the air went back up to 115 LBS, in about 8 seconds.

I have had my coach for air leaks and could not find any.

Has this happened to anyone? Do you have any idea what happened?
Rodney Nielsen
2017 IH-45
Toad: G-Wagen G63 or EQS 580 (on trailer)

Re: Losing Rear Air Pressure while traveling down grade

Reply #1 –
Could be the pressure sensor, wire connection, gauge issue OR a real issue.

Your symptoms would suggest something other than a real issue.

Start by verifying wire connections, particularly at the sender unit.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Losing Rear Air Pressure while traveling down grade

Reply #2 –
I think you had some kind of a false readout. First you maxi brakes should have come on
and second the compressor couldn't have pumped up the air that fast.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Losing Rear Air Pressure while traveling down grade

Reply #3 –
The fact that the air pressure went from 45psi to 115 psi in a matter of a few seconds, leads me to think faulty gauge.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Losing Rear Air Pressure while traveling down grade

Reply #4 –
I am not sure how your coach is wired but thinking not far off from mine.  You will have the pressure sensors located in the front cap area down low driver side. You can get to them from underneath. These wires then go to a TM102 or a TM102X Silverleaf module. This module then converts the signal from the sensor where it will communicate on the RV-C buss.  Then you dash takes this information and displays on the dash.  I would check the pressure sensors and make sure the wiring is tight and clean. Then go and located the TM102(x) and verify the wires are connected property there. I am not sure where the TM102's are located but I think I remember someone saying one is located in front of the steps under the plex glass cover that if Velcro on. The other is located back by where the water pump is. Locations in your coach may be different.

I feel if not just a software glitch, you could have a pressure sensor going bad, a TM102 going bad, or a loose / damaged / corroded cable between pressure switch and the TM102.  I would check the wiring at pressure sensor and TM102, if all looks good, I would not worry about it unless it happens again, then you would be able to do some trouble shooting.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Losing Rear Air Pressure while traveling down grade

Reply #5 –
I am not familiar with your coach but if it uses the same sensors as mine I would reccomend swapping the sensors and wait for the event to happen again. If it swaps position you have isolated the issue. No need to put back, just change the sensor. If it happens again in the original position you have proven it is not the sensor and can continue to trouble shoot it. Good luck

Re: Losing Rear Air Pressure while traveling down grade

Reply #6 –
Quote from: dsd –
I am not familiar with your coach but if it uses the same sensors as mine I would recommend swapping the sensors and wait for the event to happen again. If it swaps position you have isolated the issue. No need to put back, just change the sensor. If it happens again in the original position you have proven it is not the sensor and can continue to trouble shoot it. Good luck

Based on what Scott is saying is up front under front cap drivers side you will see the pressure switches, swap the wires for the front pressure sensor with the rear pressure sensor.  Your dash when it shows Front Air is really back air and Back Air will really be front air.  If the problem happens again and is shows as a front problem you will know you have a bad rear pressure sensor. If it show back again you will know it is in the wiring or the TM102.  I would label the wires and sensors before you start so you will know how they were ordinally put together.

As I was typing this I am now not positive these valve are under the front cap, They may be on opposite wall in the bay under drivers seat.  When I get to my coach I will have to look where pressure sensors are located.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Losing Rear Air Pressure while traveling down grade

Reply #7 –
Yes, Jack is right. I called Silverleaf to purchase the TM102 and TM 102x sensors and was informed that "they are no longer available for sale"  I must remove mine, and send it to them for repair and reprogramming. 
Rodney Nielsen
2017 IH-45
Toad: G-Wagen G63 or EQS 580 (on trailer)

Re: Losing Rear Air Pressure while traveling down grade

Reply #8 –
Quote from: RodneyN –
Yes, Jack is right. I called Silverleaf to purchase the TM102 and TM 102x sensors and was informed that "they are no longer available for sale"  I must remove mine, and send it to them for repair and reprogramming. 


 :o

Is this "no longer available" isolated to the Foretravel-built IH chassis or does it also affect the Spartan-built 2019 and later?
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Losing Rear Air Pressure while traveling down grade

Reply #9 –
I was working on coach yesterday, doing my favorite past time, chasing down air leaks.  I though I had it last week, but took the coach to Cummins to have a warranty campaign done and when I got home and check last night the HWH air tank was empty or very close it it.

I did take a picture of the pressure valves for the two air tanks.  On my coach this is on the front bulkhead in the front drivers side compartment. As you can see there are two sets of pressure valves.  I guess need to either disconnect one wire on one of them and check to see if gauge has changed, or go to schematic to find out what wire # goes to what.

Michelle, I had thought that Foretravel went away from Silverleaf but I can not find anything to back that up.  FOT's web site has the 2022 coach as the latest one which still showed having Silverleaf.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Losing Rear Air Pressure while traveling down grade

Reply #10 –
Quote from: turbojack –
Michelle, I had thought that Foretravel went away from Silverleaf but I can not find anything to back that up.  FOT's web site has the 2022 coach as the latest one which still showed having Silverleaf.

In researching, the TM102 unit is used by several other manufacturers as well, including Newmar and Newell.

I wonder if the issue is that the TM102 and TM 102X modules need to be programmed for the specific coach. 

Quote from: RodneyN –
I called Silverleaf to purchase the TM102 and TM 102x sensors and was informed that "they are no longer available for sale"  I must remove mine, and send it to them for repair and reprogramming. 

RodneyN - did you ask Silverleaf about purchasing the air pressure sensors or the TM102/102X devices?  There was another discussion topic about the reprogramming of the modules.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320