Air tanks not reaching 125 PSI.

[redstickbill]

When I start the coach the air pressure tanks will stop filling at 50 PSI. If I shut the engine down, pump the brakes to bleed the pressure down a time or two then restart the engine the tanks will fill to about 130 PSI, relief valve will relieve and pressure will settle at 125 PSI. What can cause this problem in my 2007 Dynasty.

TIA,

Bill B 07 Dynasty

[Ivan K]

My first suspect would be the air governor if your gauges are correct and you shouls also have low air alarm present at 50 psi. It is a cheap part too.

[ktloah]

What Ivan said, air regulator..

 

[Tom Cherry]

41 minutes ago, redstickbill said:

When I start the coach the air pressure tanks will stop filling at 50 PSI. If I shut the engine down, pump the brakes to bleed the pressure down a time or two then restart the engine the tanks will fill to about 130 PSI, relief valve will relieve and pressure will settle at 125 PSI. What can cause this problem in my 2007 Dynasty.

TIA,

Bill B 07 Dynasty

Be aware.  You NEED to check the system out.  The (or perhaps some, many, all?) 2007 had a different auxiliary air compressor.  If you nave only ONE drain or valve in the rear engine compartment, toy PROBABLY the “dryer included” auxiliary air compressor.  It you have two drains in the rear, you have the standard one.  A friend had a problem with his auxiliary air compressor.  It was never properly serviced of checked.  When that happens, the auxiliary air compressor will allow water to get into the rear system.  My suggestion is that if you have not drained both the front and rear recently to do that.  He had some water in the rear system and had to have it checked to make sure that it had not contaminated the rear brake canisters.  Before I did any major repairs to system, I would verify that the auxiliary compressor is working and that the dryer section is working.  He had a similar issue to yours…..his air governor would not work properly and his auxiliary would run a lot.  Your auxiliary pump has a 90 ON and 120 OFF switch.  Easy to find,  many of these switches were hung low without a moisture loop.  So when water gets into them they corrode.  Amazon has the OEM Viair switches and they are cheap.  Make sure the Auxiliary compressor is coming on and shutting off.  If not get it going or abandon the “dryer type” and install the tank with drain style used in the 2008’s.  Those units had a separate drain line and valve in the rear.

THEN start to troubleshoot the system.  A bad or malfunctioning auxiliary compressor can cost you big bucks as your air system will have to be purged and maybe completely overhaul the rear braking system.

HOPEFULLY, there is no water in the rear tank and then you can fix, if necessary, the Auxiliary compressor and then address the basics of getting it back to working.

This was a common issue, I have been lead to believe, on the 2007 and that is why a regular compressor, without a dryer, was used in 2008…

[Frank McElroy]

20 hours ago, redstickbill said:

When I start the coach the air pressure tanks will stop filling at 50 PSI. If I shut the engine down, pump the brakes to bleed the pressure down a time or two then restart the engine the tanks will fill to about 130 PSI, relief valve will relieve and pressure will settle at 125 PSI. What can cause this problem in my 2007 Dynasty.

TIA,

Bill B 07 Dynasty

As others have said, most likely your air governor is sticking.  I've seen them stick where they tell the engine air compressor to shut off thinking that the set air pressure was achieved or they stuck such that the compressor keeps running until the tank pressure relief valves open.  In most cases shutting off the engine and fanning the brakes to reduce tank pressure will get the air governor to work again.  But if you see it happen another time, get you air governor replaced.  It should be located on the PS frame rail and accessible through the rear engine bay door.

[redstickbill]

After a visit to Cummins Coach Care in Orlando, FL and changing out the air governor the problem of reaching the proper air pressure has been corrected.

Thank everyone for their correct solutions.

Bill B 07 Dynasty