BAC Forum
General Boards => Technical Support => Topic started by: Robert Mielenz on November 29, 2018, 07:09:58 PM
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My air compressor has recently started not building air after overnight shut down. I tapped on the governor and it woke up and built air. After it starts it runs normally, in and out between 85psi and 120. Took it to shop and replaced governor, same problem. Mechanic tried cleaning "dump valve" This morning it took 1 1/2 minutes before it began building air. After it starts it runs normally, builds air quickly and maintains system air. Any thoughts on what component is causing the problem.
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Maybe the Air Compressor's unloader valve (in the compressor head) is sticking.
I have a nice Bendix Air Compressor manual that show how the compressor and unloader valves work - and has troubleshooting section, but it's too large to attach here. PM me for a copy or maybe Steve can upload to the Member's tech section (I'll e-mail him a copy). Even if this is not the exact same compressor it still has some great info in it.
Good luck
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Here is the web link to the manual. Let me know if anyone thinks there is value in putting it in the Tech library (Reason for ? is that I am not aware that this is used in Beaver coaches. Pls correct me if I am mistaken)
http://www.bendixvrc.com/itemDisplay.asp?documentID=6770
Steve
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Steve, you make a good point.
I looked up the specific compressor used on our CATs and located the manual for it. The same compressor is used on the C-7, C-9, C-13 engines). Of course there is always a possibility that "a member's engine" has something different.
I am emailing you the Service Manual for the Air Compressor used on our CAT engines. That manual also has a good description of how it works and a nice troubleshooting section.
BTW - the air compressor is CAT p/n 385-0936 (OEM# 255-4160) which is a single cylinder compressor. It is actually the Bendix BA-921.
Any member that wants to verify what parts are on their engine can go to https://parts.cat.com/en/catcorp you need to register with the site, then put in your engine serial number.
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The Bendix BA 921 and 922 compressor service data sheets and application matrix have been added to the Coach Assist Tech Library. It appears all CAT engines starting with the 3126 series use one of these 2 compressors.
Mike, thanks for the data.
Steve
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Thanks to all of you. Problem solved.
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Robert,
What was the cause of not building pressure?
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It appears that the compressor unloading valve had carbon build up and was sticking. We gingerly applied cleaning solvent to the valve as the compressor was working. It appears to have cleaned the valve to the extent it now is much better, but not completely fixed. It is still slow waking up.