Air Pressure Slow to Pick up.

[GringoPhil]

Hi all,

Fifty three degrees here today, started the coach ran for a while would not pick up air pressure past thirty pounds. Last month was slow but pickup air to 120+.

THANK YOU

[MrE]

There's a pressure relief valve on the bottom of your air dryer, located drivers side engine compartment. With the motor running, stick your hand under it to see if it's stuck partially open. If so you can tap on it with a wrench or small hammer to see if it closes. If it's oily it probably means that your compressor is going bad.

[GringoPhil]

Jon,

Your quick to respond :thumbup: I'll inspect it now. Let's hope for an easy fix.

phil

[NewellCrazy]

I agree with Jon, Try that first and let us know whatcha find.

Sean

[folivier]

Someone recently had a similar situation. There is a controller on the engine air compressor that is a common $15 part (any truck place should have it) that controls compressor cycling. Is air exhausting from around your air compressor when it tries to build pressure?

[77newell]

Hey GringoPhil: sorry to hear of your troubles. Either the compressor isn't putting out enough air or you've got a large leak. If once pressure was previously built up - though slowly- it didn't drop precipitously once the compressor unloaded (turned off) then you don't have a leak large enough to cause your symptoms. Another way to test this is to hook up shop air to the system, charge it up, shut the supply off and see how fast the pressure drops.

If you find that a leak is not the problem then I would be exploring the compressor and its governor. Bendix has provided a great troubleshooting guide for this in the following PDF file:
http://www.bendix.com/media/documents/products_1/compressorsgovernors_1/troubleshootingguide.pdf

This guide has some relatively simple test procedures for determining that the compressor is or isn't working OK. If it is OK then the governor is gone to .... wherever it is that governors go when they are shot.

[MrE]

GringoPhil, I made an assumption that your compressor is direct drive, your symptoms are also what would happen if your belt was loose when it's belt driven.