I installed a new pressure regulator including a new line from it to the compressor. When I start the truck it builds to 120 psi. As I drive and use air it continuously fals to below 60, the compressor never comes on. What is it actuating in the compressor head? Can something be stuck or not working in the compressor...When I got this in January it would build to 30 psi stay there for a while then got to 120. Then for a while it would build to 140, causing the pressure relief valve to open. It did a few other odd things causing me to put in this new regulator...When I installed this it would go to 130, too high. Per the 34 manual I started adjusting it 1/4 turn at a time counter clockwise, screwing out, to try to lower the pressure. The pressure just kept getting higher. Finally tried turning it clockwise and this lowered the pressure. Can someone confirm the 34 is wrong and it is closkwise, screwing in, to lower the pressure.
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New Air pressure Regulator Not Working
- Thread starter renovate7
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- Interlachen Fl.
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If you put a new governor on it and are still having issues, it might be the unloader in the compressor. I have never had one of these compressors apart, but, if it is a single cylinder Midland, they are kinda hard to find parts for, it might be easier to get another compressor, but, you can take the plugs out of the top and see if there is junk in it...be careful, there is a spring in there. If it is the 2 cylinder Bendix, they should be under the air inlet. Pull it off and see what's there. One more thought, if the line from the comp. to the gov is pinched or blocked with goo, you can build too much air...the signal from the gov. back to the unloader isn't getting there, so the air keeps building till the tank relief goes off. Try taking the line off at the gov and the comp and put compressed air back thru it, and check the fittings for carbon, corrosion, dirt,etc. Do this first, then go into the unloader. Keep us posted
Will
Will
BEASTMASTER
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follow the line from the gov. to the top of the comp., maybe 2 -7/16 bolts hold it on ? under that housing is two little valves and springs. on mine one was bent and stuck ,so i staightened it and oiled it , put it back together and behold ,works like a charm. no more listening to that pressure relief blowoff. 
- 8,539
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- Monrovia, Ca.
That would be the unloader that was bent.
Thanks for the input. My 20 manual, dated 10/91 is WRONG about adjusting for pressure. It says the opposite of what that Bendix spec says... I looked in a parts manual and it showed the unloader on top of the compressor. I think that may be where the problem is. This truck sat for up to 2 years before GL sold it in January. Having grown up in the forklift business I know the worst thing you can do for any equipment is let it sit. Seals dry out then leak, shafts corrode, moving parts stick, water condenses and builds up in tanks. I think I have/had wheel cylinders hanging up just because of this. My brakes seem better than they were making me think a cylinder is working again. I've received 4 wheel cylinder kits and 2 new cylinders and am planning to inspect the brakes soon...I'm going to pull the unloader and will report back in.
So far so good. I pulled the unloader on this single cylinder compressor and found a lot of surface rust etc. The two pistons/plungers would move up and down as I pushed on them with my finger but there was a lot of crud around them. I took them out and cleaned them and the compressor with some 0000 steel wool. I put some PB Blaster in the little holes and worked the pistons a few times. Seem real smooth now. I powered up the Deuce and let the pressure build. At 120lbs the needle took a solid bounce and stopped. Bled off the air at a gladhand to 80 psi and the compressor kicked on and built to 120 again. Did this few times. All seems OK now. This has probably been a problem since I got this and explains my erratic air pressure...Does anyone know what these pistons are actually doing? The unloader didn't seem to have any moving parts in it or anything tightly sealing to theses pistons.
Well I'm learning more and more about my duece. It has been making an air sound and clunk since day 1. I now think it is from the air regulator and more specifically the "cut-in". It cuts-out perfect around 120psi, but the pressure never really drops much. Stays pretty steady around 120. It just make the air sound about every minute then follow by a "cluck" inside the regulator. I'm thinking it needs lube or the cut-in is too high. Any thoughts.
PS: I was glad to find the noise was coming from it and not the front drive!!!
PS: I was glad to find the noise was coming from it and not the front drive!!!
My solution was to install a second new regulator. NAPA has them for $18 plus a $4 core charge. The new one works great. Initially it built to 130psi then dropped to 110 before cutting back on. I turned the screw about 1/2 turn and it now turns on at 100 and off at 120. The manual says each 1/4 turn of the screw equals 4 psi. It sounds like your regulator is not working correctly. Did your truck sit for a while at GL etc? I'm finding that a lot of my little leaks are most likely because this truck sat for 2 years or so before GL sold it. The worst thing for any seal is to just sit and not get some lube from whatever they are trying to hold back. They will stick to the metal, dry out etc. I grew up in the forklift business (Material Handling Industry). They are nothing but a leak waiting to happen.
MitchG
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Do you have a oart number for that air regulater from NAPA?
- 7,058
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- Mid Hudson Valley NY
Anyone got pics of the unloader and the like to help some of us see what exactly it is?
Jake0147
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- Panton, VT
Without being too specific to this compressor, the general idea of the "pistons", or valves, is that they function like glorified reed valves, or one-way check valves. When the piston in the compressor (like an engine piston) moves down, air is drawn past the intake valve, which spring closes wieh the air stops moving. When the piston moves up, air pressure forces open the outlet valve, which leads to the air line to the tank. The unloader prevents the intake valve from closing, so when no air is called for, no pressure can be developed in the compressor.renovate7 said: