Need Help locating Air Brake Governor

[Djmckee]

I have a 1999 Holiday Rambler Endeavor
275 hp Cummins
Freightliner custom chassis

I am trying to locate the Air Brake Governor reading other post it should be on the passenger side rail. Either not there or can’t find it. It could just be me

[wolfe10]

The governor turns on and off (actually unloads/loads) the engine driven air compressor.


Should be near the engine driven air compressor and connected with smaller gauge hoses. The larger gauge hoses from the air compressor go to the air dryer.


What is your symptom that you feel the governor is an issue?

[Djmckee]

Pressure stay at 25 psi. If I run 2000 rpm I can get up to about 50 psi. Before this while driving RV started pegging out the air gauges purging every few minutes then quit going up to proper pressure

[wolfe10]

Could be the governor.


But, also could be a bad air dryer. When was the last time the air dryer was serviced/replaced?



With the engine running, can you hear air escaping? If so where?


Should be easy to determine if this is a gauge mis-reading or a real PSI issue, as 25 PSI will not release the parking brake!

[twinboat]

You most likely blew a line from the excess pressure.
A bad governor will not do what your experiencing now.

The flexable line between the compressor and the air dryer would be the one to check. It will only leak with engine running and hard to hear.

Once that's repaired, then find out why you were building so much PSI. That may be another leak on a small control line or air dryer control line, or air dryer.

[Djmckee]

It’s PSI yes the parking brake will not release

I have been around up and under several times I can’t hear any leaks. I was going for the cheapest fix first. Air Dryer next if this don’t fix it.

[Djmckee]

I will check that out

[Skip426]

Here's a 99 Freightliner air system diagram , in the fine print on the compressor it shows the governor mounted on the side of the compressor , and that's it's location on my Caterpillar engine mounted compressor . Green box in picture.

Also info from Freightliner on servicing the air system dryer .
My dryer is on the inside of the drivers side frame rail , beside the transmission.

EDIT: If your governor isn't on the side of the compressor , then follow the 1/4" air line from the air dryer towards the compressor , it's along that route somewhere.

[twinboat]

Just changing parts based on how much they cost is not the way to fix stuff.

You go thru the steps of troubleshooting.

I'll bet that 90% of air compressor governors changed are for no reason .

If your going that way, it may be bolted right on the air compressor itself or follow the smallest line leaving the air compressor. That will lead you to it.

[Djmckee]

Thanks for the help. Believe me when I say I am not into changing stuff we don’t need to. I have followed Twinboat’s advice I have started with the Air Dryer area checking for leaks. With the engine running pressure at about 35 psi i have started spraying soapy water there are no leaks around the Air Dryer. My next focus is to follow the 1/4 line to the Governor from Air Dryer. Just ran out of time. So I will continue that task. Before I change anything. I have never worked on Air Brakes prior to this so this all all new to me. I have only own the Home for 30 days so I don’t have all the servicing records from the PO. I really appreciate the help given here. I still couldn’t Identify where the compressor is at. I did locate the Air Dryer in the driver side behind the rear axle so starting there. I am looking for leaks first. Also my Air Bags are not inflating. Still can’t hear any leaks at this time

[Skip426]

The air suspension , is isolated from the air brake system by a PPV ( Pressure Protection Valve ) the suspension won't air up until you get to 70 psi in the front air tank .
The PPV is in place so , in the event of an air suspension bag blow out , you will still have air pressure for brakes.

Air compressor on the 5.9 Cummins , in a motorhome is on the passenger side , at the engine front , mounted to the timing gear case .
Blue box in photo .
Red box , power steering pump .
Yellow , air compressor , air supply hose ( from intake manifold)
Green box , fuel lift pump.

The dash air conditioning compressor has been removed from the engine in this picture , so if your looking down from the top the dash air conditioning compressor blocks the air system compressor from view.

BTW. Could you take a few mins and update your signature line , some members might think your still working on your 1992 and not reply .

[Dunrollin]

I had similar symptoms with too much pressure but the air dryer failed to purge, or do anything for that matter. In my case it was a nylon air line that had burst. I found it by starting at the air dryer and feeling it as it went upward. Easy repair on the air line but the dryer was in terrible condition and I replaced it as well.

Also I found the tanks needed drained badly, one had a lot of water. All this was when I acquired the motorhome.

Photo of the airline attached.

[Djmckee]

Finally had a chance to work on again today I found a broken line just like twinboat said between the Governor and Air Dryer. I fixed that no change yet. I did a bypass on the Air Dryer no change. I was able to pressurize the system from air dryer to the system with my external compressor everything work as it should. Held pressure at 120. So my problem still not shoved I am still trying to troubleshoot the system.

[twinboat]

It still leaves the larger line between the compressor and air dryer.

The failed governor line caused the high pressure you were experencing.

The high pressure may have blown the main line.