Another Air system problem

[c210pa18]

Air Problem,   several weeks ago I changed out two PPV’s on the rear air tank and one on the front tank.  The two rear units were leaking.    Now after a couple of days the pressure drops to about 65lbs and doesn’t seem to go any lower or maybe just goes down much slower after 65 pounds.  I have been working on the MH off and on so it has been getting started every few days recently.   A few days ago I had it up to the shop working on it and when I started up and started to drive back to the storage shed, about 120 yards away from the shop, the pressure in the rear tank dropped to around 65 lbs I stopped and the pressure would not come back up.  I fiddled with it, pumped the brakes a few times and the pressure went down some more but would not build more pressure.  In my continued fiddling, for whatever reason, I pushed the Air Level button and it started building pressure back to normal.   So this morning I decided to get the MH out of the shed and try to figure out want is going on.   Everything worked as it should went for a drive (8 miles) I could not get it to fail.  I parked it by the shop and worked on some other things.  When I started it up a couple hours later, it was a repeat of what happened a few days ago.   I can’t find an air leak although there must be a fairly big one to leak as fast as the compressor will pump air.  It only leaks down to 65 lbs unless I press on the brake pedal then it will go on down,  there seems to be an alarm horn in the back maybe near to rear air tank that goes off when the pressure gets down low enough, I've never heard that alarm before today.  And again if I turn on the air leveling it will build pressure again.  I am stumped.  Is there a valve that is stuck open that closes when I turn on the air leveling?  It seems most likely it is a rear airbrake problem but what does that have to do with the air leveling system?  Please help.

[Frank McElroy]

My first thought is a sticking air governor.  Air up then fan the brakes to find the air compressor cut in pressure.  I bet it's way too low.

[c210pa18]

I will go out and try that what should the cut in pressure be?

 

[Frank McElroy]

3 minutes ago, c210pa18 said:

I will go out and try that what should the cut in pressure be?

 

Typically cut-in pressure is 110-115 +/-.

[c210pa18]

Ok,  I went out and took it down to 60 then 50 then 40 at 40 pressure started to go up.    However,  I'm now wondering if I waited long enough on 60 and 50.   After the pressure came up to 130 and the release popped off, I took it down to 110 and the pressure came up,  then down to 120 and it did not come back up   Then again down to 110 and it built back up to 130 where the release popped off.    Maybe the air governor is not consistent??

[Frank McElroy]

Yep, it sounds like a sticking governor to me.  I'd replace it.

[c210pa18]

Ok thanks, Frank.  I will get one and replace it.   I'll let you know if that solves the problem.   Not sure what the connection would be with the Air Leveling being on or off.  That gave consistent results and did not drop the pressure readout but did result in the pressure building up again.

[Frank McElroy]

25 minutes ago, c210pa18 said:

Ok thanks, Frank.  I will get one and replace it.   I'll let you know if that solves the problem.   Not sure what the connection would be with the Air Leveling being on or off.  That gave consistent results and did not drop the pressure readout but did result in the pressure building up again.

When you turned on the air leveling system, it was like fanning the brakes - in effect you dropped the air pressure low enough for the governor to kick in and the compressor to start build up air pressure.

[c210pa18]

Thank you, Frank!  Replacing the governor seems to have solved the problem.

[Frank McElroy]

Thanks for posting an update.  Your description of the problem and the solution should help others who search the forum in the future with a similar issue.