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Engine air compressor governor
#1
After driving 360 miles today we stopped at a roadside RV park in Glendo WY (middle of nowhere). I leveled the coach with slides in as we were leaving early tomorrow morning. After about an hour the level system kicked on the 120v air compressor. I decided to start the engine and go back to travel mode and use that overnight. The problem was that the air system would not build above 90 psi. I confirmed that I could not hear air leaks with and without engine running. After conversations with Tom, Bill, and Steve. We decided it was the governor, or at least that was a $20 part and easy to install. 30 miles away was O’REILLYS that had the part. I tried my best to match the plugged and 2 airline holes. The old governor has blue cap like in very detailed picture, and the new governor has the black cap. All holes on both match.

After new install I now have the opposite problem. The governor is not exhausting by 135psi when I shut off the engine. Watching videos I suspect that the exhaust port plastic filter cover that I moved from old to new is the culprit, but don’t know and it is too late to test. The video says that port should be open but he has seen dust covers and filters in some brands. So, I will test with the exhaust port clear first thing in the morning.

The park is full and we are supposed to vacate tomorrow, so I need to get this fixed ASAP.

Questions:
1. What is max safe pressure to allow it to go before I risk blowing something?
2. If exhaust port is not the fix, there is an adjustment screw I can try but it should have been set by the factory. Should I go buy another? NAPA opens at 7am.
3. Other ideas?

Video


Thanks to Tom, Bill, and Steve for consultation today!


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Mike & Jeannie Ginn
2000 Newell #555
2013 Chevy Avalanche
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#2
different trucks take different pressures. you should just adjust the pressure on the governor

tom
2002 45'8" Newell Coach 608  Series 60 DDEC4/Allison World 6 Speed HD4000MH

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#3
One port on the governor goes to the 'unloader' in compressor head. This tells the compressor to go to limp mode. Make sure this is correct and no junk in either the comp, or the governor itself. Verify that the lines go to the proper places.( Air tank and dryer)If thats good and all the ports are plugged the same as the old one you should try to adjust pressure. You were prob. as high as you was\nt to go at 135. I just changed gov. out on the MCI and the pressure was set about 130 from factory. Turned it down to just below 120. Good luck. Mark

Edit to say this is a well done video. To the point and covers all the bases.

Also sometimes these governors can be fixed just by turning the adjustment screw in and out. Not worth the trouble for a $20 part but works sometimes when parts not avail.
Mark and Marian

1987 #125
Pace 28' stacker

Gray SK  Maricopa AZ
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#4
I made the adjustment and on the road again :-) it is frustrating that a part labeled as 110-120 psi would not be set from factory. I will post more later, but I recommend every by a spare part. It is easy change and adjustment once you know what you are doing, and this part can leave you on the side of the road. I replaced this a year ago, so would not recommend buying the blue plastic cap version. Go for the black cap. I will post part number later

Thanks to all that helped!
Mike & Jeannie Ginn
2000 Newell #555
2013 Chevy Avalanche
Reply
#5
Here is some more info on my experience and how to adjust the pressure. 

My new part from O’Reillys Is Midland RB18530 valve governor D-2 all ports 1/8” NPT 100-120psi. Tom found one on Amazon which looks just like it “D2 Truck Air Governor Bendix Midland Frieghtliner”. This has a black cap and is adjustable by loosing the lock nut the turning the screw clockwise to lower the pressure. Be sure to tighten the lock nut. The old blue cap unit does not look adjustable or something was broken off mine in the picture. Freightliner installed mine a year ago and boy am I disappointed in them. First, they would not let me watch, now they supplied an inferior part.


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Mike & Jeannie Ginn
2000 Newell #555
2013 Chevy Avalanche
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#6
so even though it says it has a range of 100 to 120 psi, you adjusted it up to 125 or so?

tom
2002 45'8" Newell Coach 608  Series 60 DDEC4/Allison World 6 Speed HD4000MH

Reply
#7
(07-14-2018, 10:53 PM)encantotom Wrote: so even though it says it has a range of 100 to 120 psi,  you adjusted it up to 125 or so?

tom

No, I adjusted it down from like 135+ to 125. I really don’t know how high it was set because when it hit 135, I shut the engine off.
Mike & Jeannie Ginn
2000 Newell #555
2013 Chevy Avalanche
Reply


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