Rob Posted October 6, 2010 Share Posted October 6, 2010 This R612 is making lots of air pressure, to the tune of blowing the relief valve on the tank. I adjusted the governor with no luck, so I replaced it with a fresh reman unit. It will still make air with all settings until the relief valve on the tank opens. I disconnected the unloader line from the governor that runs to the compressor head and it unloads as it should, according to the adjustment screw setting. I'm thinking the unloader valves in the compressor head are not functioning. Has anyone seen this happen before? The air compressor seemed to work fine a couple of days ago.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/16029-too-much-air-pressure/ Share on other sites More sharing options...
rhasler Posted October 6, 2010 Share Posted October 6, 2010 This R612 is making lots of air pressure, to the tune of blowing the relief valve on the tank. I adjusted the governor with no luck, so I replaced it with a fresh reman unit. It will still make air with all settings until the relief valve on the tank opens. I disconnected the unloader line from the governor that runs to the compressor head and it unloads as it should, according to the adjustment screw setting. I'm thinking the unloader valves in the compressor head are not functioning. Has anyone seen this happen before? The air compressor seemed to work fine a couple of days ago.RobIt seems like I had one a while back that had the siganl line to the governor pinched part of the way shut during a frame rail job that did something similar. Quote "Mebbe I'm too ugly and stupid to give up!" Link to comment https://www.bigmacktrucks.com/topic/16029-too-much-air-pressure/#findComment-64842 Share on other sites More sharing options...
theakerstwo Posted October 6, 2010 Share Posted October 6, 2010 Rob to test it you need to air up the unloader port were the governor line connects and then put 100 or so air pressure to the unloader valves thru the port. It should be able to hold pressure if you can cut the supply off to the ports and see if the pressure holds up. The unloaders are only small pistons with o/ring seal and if they leak by the the unloader may not be unloading completly.I have a shader valve that i can screw in to the port and air it up and check the pressure in a few seconds with tire gauge.If it is a midland compressor you can remove the valves which are under the bolt on plate on top of head. If it is a bendix go thru the intake port to remove them.Easy to do and the field maintence kit will have them in it.It takes air to unload the compressor. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/16029-too-much-air-pressure/#findComment-64843 Share on other sites More sharing options...
Rob Posted October 6, 2010 Author Share Posted October 6, 2010 Rob to test it you need to air up the unloader port were the governor line connects and then put 100 or so air pressure to the unloader valves thru the port. It should be able to hold pressure if you can cut the supply off to the ports and see if the pressure holds up. The unloaders are only small pistons with o/ring seal and if they leak by the the unloader may not be unloading completly.I have a shader valve that i can screw in to the port and air it up and check the pressure in a few seconds with tire gauge.If it is a midland compressor you can remove the valves which are under the bolt on plate on top of head. If it is a bendix go thru the intake port to remove them.Easy to do and the field maintence kit will have them in it.It takes air to unload the compressor.Hi Glenn, I have a few Schrader valves with 1/8th NPT threads and will do as you suggest. The line from the receiver to the governor is connected and routed properly without restrictions. The governor does pass air pressure to the unloader port when it's setting is reached. I suspect the unloader pistons are leaking by their respective "O" ring seals as suggested. I don't think this is a Bendix compressor as the unloader port is a bolt on type plate with three capscrews retaining it to the head. It uses a #4 Stratoflex hose connected to the unloader port. Thanks,Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/16029-too-much-air-pressure/#findComment-64849 Share on other sites More sharing options...
Greg Rider Posted October 6, 2010 Share Posted October 6, 2010 Is it making too much pressure or do you have a bad relief valve? Quote #1 on A-model registryIf I drink because of work, why can't I drink at work? Link to comment https://www.bigmacktrucks.com/topic/16029-too-much-air-pressure/#findComment-64872 Share on other sites More sharing options...
Rob Posted October 6, 2010 Author Share Posted October 6, 2010 Is it making too much pressure or do you have a bad relief valve?The valve is relieving at 155psi by the gauge I've installed into the tank. I removed the drain cock installed the gauge into the port. I agree with Glenn as it takes air pressure to raise the pistons in the compressor head. If the rings are passing air the pistons cannot lift thus the compressor will not unload, or send air to atmosphere but rather to tank.The dual needles of the air pressure gauge in the dash will peg against the "0" stop after wrapping completely around the face.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/16029-too-much-air-pressure/#findComment-64873 Share on other sites More sharing options...
Greg Rider Posted October 6, 2010 Share Posted October 6, 2010 If you're getting that much pressure on a known good gauge then it is probably the unloader. That's my $.02 of opinion,,,that's all I can afford! Quote #1 on A-model registryIf I drink because of work, why can't I drink at work? Link to comment https://www.bigmacktrucks.com/topic/16029-too-much-air-pressure/#findComment-64877 Share on other sites More sharing options...
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