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Air governor replacement
I had been noticing my air dryer purge more frequent than I would like to hear lately. Between Fort Worth Prevost and myself fixing any air leaks that had been discovered over the last year, draining the air tanks often, and changing the dryer filter, I figured I would try something else.
For less than $100 (just about cost to drive it to Prevost) and 10 minutes of my time, I replaced the D2 governor on my compressor. I took off the old one which was rated at 105-125psi and put on the new one which is rated at 100-120psi. Im not sure if governors can get old and tired but the new one seems to be performing great. The best way I can describe the result is it appears to be much more responsive and the dryer no longer purges near as frequent.
I had some reservation about going with a governor with a different cut in/cut out rating but as easy as it was I thought I would give it a try. When I park the coach at my house, I have to overcharge the airbags to back in my driveway. A handfull of times the rear of the coach would overcharge but the steer axle would remain at ride height. Troy at Liberty suggested I turn the governor up to a higher psi to get the front bags to overcharge because the steer axle was the heaviest (in terms of equalizing air pressure) part of the coach and would always be the last to rise. I never did for three reasons: its hard do without having to remove the governor entirely; I rarely ever need the coach in my driveway at home; and 90% of the time the coach lifted without an issue. Having a cut out pressure of 120psi, the front of the coach has lifted everytime with no issues; without timing it, quicker than ever before.
We always carry a spare governor in our big trucks. By far the easiest fix that anyone can swap with 2 wrenches and otherwise leave you unable to build air pressure out in the middle of nowhere.
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13 Replies
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The gonernor is adjustable Patrick, so you can turn it up at tad if needed. Prevost won’t go beyond 125 psi, but I just spend some time with a Liberty owner that told me Liberty turned his up to 140 psi for more front air bag lift when leveling.
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A lot of the devices in the pneumatic system are pressure limited to 130 PSI. I know Prevost will go to 130, but am not aware they want to go higher.
Maybe I am reading something into that that might not be the problem but one thing that would cause short cycling of the compressor is water in the air tanks. With reduced volume due to water there is less volume of air to compress. That would also be consistent with slow lifing in the front because the pressurized air in the system would be limited in volume.
Have the air tanks been drained routinely and has the dryer been serviced regularly? And her is the $64,000 dollar question: Has the Liberty installed spitter downstream from the compressor been checked for proper operation? Those are a rather unreliable device and if they are not functioning a lot of water can be delivered to the accessory tank along with all pneumatic devices including the suspension.
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If there is any water in the system, I cannot find it. Fort Worth Prevost had the coach about 45 days ago (3500 miles ago) and installed new petcocks on all the tanks including ping tanks, leveling valves (2 in the rear and 1 in the front), new desiccant filter on the dryer, etc. I have the bill to prove it!
I religiously drain the aux. compressor tank along with the Norgren water separator. I have never found water come out of the tanks except for a tiny bit of moisture shoot from the aux. tank that is dries before it hits the ground.
Jon, I know you always refer to the “spitter,” but where exactly is it located and what does it look like? I have turned everything that has a drain or petcock on it and never found water. Ive never found anyting on the coach to be a “hack job” or installed wrong or out of the scope that Liberty or Prevost would find acceptable.
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My 2012 Liberty is set to cutout at 135 PSI.
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The “spitter” on both my XL and XLII was located on the rear (RH) bulkhead in the steer compartment in the area of the well pump pressure switch. It is in line with the solenoid valve that functions as the check valve in the air line going from the aux compressor.
The “spitter” has a bowl that can be removed and it is about 1″ in diameter and about 3″ long. The fixed part or head of the spitter is unpainted aluminum.
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Where is the air governor located?
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It’s on the engine driven air compressor.
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Some later models, such as possibly Jerry’s coach will not have a governor located at the comprtessor and adjustable, but will instead have the Haldex dryer with the built in non-adjustable pressure governor.
If you get the sense I feel playing with the pressure to get a bus to raise up in the front is not the best decision you are right. If I rule out restrictions to the air flow a slow rising front end is an indication the front axle may be overloaded. The obvious solution is to reduce the weight if possible. If that is not practical you can encourage the front to come up to ride height faster by lifting the tag simultaneous with trying to raise the front. Once at the correct ride height even coaches with overweight axles will stay at the correct height.
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Jon, I agree with you on the air pressure comment in the way of raising the air pressure to raise the coach. I just noticed mine seems to raise the front quicker than before even with only 120psi. I should be good on the weight and I know Liberty stresses a balanced coach that does not exceed the axle rating. In fact when I was up for tires they told me not to go with 365s but to stay with the 315s. This is my particular coach full of water and fuel:
Steer Axle: 16,340lbs
Drive Axle: 20,400lbs
Tag Axle: 12,460lbs
I think Prevost rates the front axle for 17K. I guess if we get pulled into the scale I’ll have my wife get up and go lay on the bed(I hope she never gets on PC and sees this)!!
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Patrick,
Can I get your wife’s e-mail address?:)
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I have printed this post from Patrick, laminated it in plastic and am awaiting the opportunity to meet his wife. Of course the laminated plastic version will never come out of my pocket if Patrick wishes to bribe me.
I am very interested in certain expensive Bourbons. I like small things like a Rolex, I wouldn’t mind having Patrick wash and wax my coach, etc.
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HaHa. I guess the edit button won’t do me any good now!! A wash with your water and your wax is about all I can offer. All my cash is spent on a 50000lb piece of stainless; but I keep it clean.
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Bring your own ladder Patrick. I’ll gladly supply the water and wax.
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