1981 MCI 9 air compressor governor adjustment

[RickB]

Hey all,
Any advice on resetting my air compressor cut out pressure? It is currently set at 135 psi and I have been reading that 115-120 is max recommended pressure. I have a 1989 manual but it is a different model of governor.
Any thoughts???
Thanks, Rick

[Dallas]

Your air compressor is mounted to the rear of your engine. Your air compressor Governor is mounted on the rear of the compressor.

It's called a Bendix D-2.

There is a blow off valve set for 150 psi on your wet tank. If the air pressure reaches more than 150psi, the blow off valve will blow off and sound like a jet engine in afterburner mode.

To adjust the governor, remove the black rubber cover and turn the screw one way or the other.

If you don't have a governor that looks like the one pictured.. change it...

[niles500]

A 1/4 turn on the adjustment screw is approx. 4 or 5 pounds and 125 lbs is max pressure - HTH

http://www.bendixvrc.com/itemDisplay.asp?documentID=2382

[RickB]

Unfortunately my governor doesn't look exactly like the one in the picture. Mine has a removable soft rubber end instead of the finned type end in the picture. Other than that it looks exactly the same as the picture. Is mine an older model or does mine just have a different cover. There is a circular metal mesh under the soft cover. Do I just try and turn the bolt in the center to adjust it? Thanks for your help

[Dreamscape]

Yes, just turn the bolt head until you see it increase or decrease. Then you can adjust for the final press you want. You can hear the cut off or listen to the air compressor, it sounds differant when building pressure as opposed to not.

HTH

[buswarrior]

Hello Rick.

All sounds good.

I'm just writing this for those who may not know the story.

You already know that you have to drop the air pressure low enough to get the compressor to start and build again after each adjustment attempt.

Once you have your top pressure where you want it, confirm that cut-in is 20-25 pounds below. This spread is not adjustable. Anything much further from that, it should be replaced.

The governor is the mechanical switch that determines when the compressor will pump and when it will not. To check the settings, you have to lower the air pressure, noting where the "switch" turned on and then let it pump and it will show you when it's going to cut-out.

happy coaching!
buswarrior

[Dallas]

Rick,

Just as a thought, since usually D-2 governors don't need adjustment...

Are you reading from the dash gauge or did you install a KGU (Known Good Unit) between the compressor and the wet tank?

It could be that your gauge is just inaccurate.

One clue would be that the cut in and cut out pressure would both be equally as far off.

If you adjust your governor to read correctly on the gauge and the gauge is wrong, you aren't doing yourself any favors. Make sure the governor reads between 120-125 psi.

Dallas

[TomC]

When it is cold, the pressure will be higher than with a warm engine since the spring will relax a bit when warm.  Also of importance-do you have an air/water separator?  Typically you can tell if you do or not by watching the air pressure come up to maximum.  If you have an air/water separator, when the compressor turns off at maximum pressure, you should here a definite release of air pressure-that's the air/water separator spitting out the water for that one cycle.  If you don't have a air/water separator, get one-it will save lots of money in the long run.  It is so important, it is standard equipment on Freightliner heavy duty trucks.  Good Luck, TomC