Air Governor

[redbus]

I put on a new air governor this morning solving the problem I had but now the pressure seems really high to me. With the old governor the dryer would spit at 115psi,now it spits at 135psi. Is this too high?

[bevans6]

It is adjustable.  Part of the installation process is adjusting it, i would think.  On mine, the adjustment is under a cover, there is a nut and screw.  You would back off the nut (take off some pressure on the spring) to lower the pressure.  120 psi is a common cut-out pressure, 135 is not unknown, but seems a little high to me.  Double-checking the gauge accuracy would seem to be a thing to do as well.

Brian

[redbus]

Thanks Brian
How many turns would you recommend backing it off before checking again?

[JackConrad]

Terry,
    Unscrew the cover on the end of the governor.  Loosen the locknut, turn the screw counterclockwise and re-tighten the locknut.  I would not lossen more than 1/8 turn at a time. You can always turn a little more if neccessary. After you adjust, pump the brakes enough to drop the air pressure, then see what it pumps up to. When you have it adjusted, re-install the cover.  Jack

[bevans6]

I would do two turns to start, and see what happens.  The directions from my manual are:  Loosen the adjusting screw nut (a lock nut, basically) and turn the adjusting screw.  If the cut-out pressure is higher than desired turn the adjusting screw clockwise with a screw-driver until the governor cuts out at the desired pressure.  Tighten the lock nut.

Check your cut in pressure after you do this.  The cut in pressure should be 25 psi lower than the cut out pressure.  If your bus was a MCI, the recommended cut out pressure is 115 - 118 psi.  The range between cut in and cut out is built in and there is no adjustment for that.

Jack, I'm reading the manual as I type, it says turn the screw clockwise to lower the pressure.  That would raise the spring cap, reducing the preload on the spring, so makes sense to me.  Just noting that as your advice, which I would always value, is opposite to the manual.

Brian

[JackConrad]

You are coorect, I should not trust my memory at my age.  I am pretty sure the cut in and cut out pressures cannot be adjusted separately. You adjust one and it changes the other by the same amount.  Jack

[bevans6]

I think you are probably right about the amount to start with, 1/8th to 1/4 turn rather than two turns.  After you make the first adjustment you would get a sense of how much to turn for how much pressure change, it will be pretty linear as long as the spring is reasonably pre-loaded.

Brian

[redbus]

Jack and Brian
Thanks for the valued advice. I will adjust it tomorrow. I thought 135psi was a little high. I have had this Bus 7 years and still need a lot of advice.Thanks again.

[white-eagle]

that's probably not the only thing you need advice on.  i'd at least take Connie out for Lunch, even if she's not your mother. 

[gus]

My new governor also decreases the max press when turned CW.

Mine is set at about 105 psi which is plenty for my lightweight bus but I would think that 120 would cover almost any bus. My theory that any excess max pressure just invites more leaks!!

I could never find a way to control the cut-in pressure, don't think it is possible with the top adjustment anyway.

[redbus]

Yea Tom I'm sure it will be lunch at least. After 46 years I guess she deserves that much. Oh by the way Fran has a rough row to hoe also.

[buswarrior]

FYI, some of the newer equipment is running somewhat higher pressures, in the 130 lb cut out range.

It will not be unusual to find ones pre-set to these higher values moving forward.

As noted, there is only one adjustment on an air compressor governor.

The spread between cut-out and cut-in should be somewhere in the neighbourhood of  20 to 25 lbs, nature of the beast, and not adjustable.

Turning the adjuster will move this spread up and down, to your liking.

So, you may choose your minimum or your maximum, but not both.

happy coaching!
buswarrior

[niles500]

If memory serves me correctly (and that is not a foregone conclusion) it's 3# +/- per 1/4 turn and cut in is set @ 80% +/- of max cut out pressure - HTH & FWIW

[bevans6]

What are the DOT specifications for air pressure cut-in or cut-out pressures?  Are there legal limits? 

Brian

[redbus]

I adjusted the governor to cut-out at 120psi but I still have the original problem so I will start on the air dryer next.