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I'm having with air pressure on a 379 Pete with vin #

I'm having with air pressure...
I'm having with air pressure on a 379 Pete with vin # ***************** it's only building 90 psi on primary side no air leaks and I have tried a new compressor, still 90 psi no secondary at all no air leaks none found at all
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Answered in 3 minutes by:
5/10/2019
Technician: Mike Mcmillan, Shop Foreman/Triage Tech replied 3 years ago
Mike Mcmillan
Mike Mcmillan, Shop Foreman/Triage Tech
Category: Medium and Heavy Trucks
Satisfied Customers: 6,440
Experience: Volvo/Mack Master Tech, Certified with Cummins, Eaton, GM, Hino, Detroit Diesel
Verified

Hello and thank you for using Just Answer. My name is ***** ***** I will be assisting you with your question. I am sorry that you are having issues with your Pete. Please allow me a few moments to look over your question and I will be right back with you. Thanks.

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Customer reply replied 3 years ago
Have you come up with anything yet on this
Technician: Mike Mcmillan, Shop Foreman/Triage Tech replied 3 years ago
I am sorry I must not have hit send. Is the air compressor getting any air to the unloader valve when it hits 90? Have you tried bypassing the air dryer? There is a check valve between the wet tank and primary tank to keep from back feeding but that doesn’t seem to be the issues here.
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Customer reply replied 3 years ago
the air compressor is fine its brand new and cant bypass the dryer it has the ad9 dryer on it not able to bypass that one
Technician: Mike Mcmillan, Shop Foreman/Triage Tech replied 3 years ago

You can bypass the air dryer on an AD-9. Just connect the inlet and outlet together. This is just to tell if you have a restriction in the air dryer itself, or if the valve is not holding pressure against the inlet. When the pressure hits 90 are you getting any air out of the unloader valve line?

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Customer reply replied 3 years ago
It was doing the same thing with the original compressor so I put a new compressor on it because it had over 100,000,000 miles on it, but before i changed it i hooked shop air to the the truck and both primary and secondary built up fine
Technician: Mike Mcmillan, Shop Foreman/Triage Tech replied 3 years ago

The unloader line is what signals the compressor to stop pumping, This line is from the dryer or a direct feed to the air governor. Which in turn applies air pressure against the piston in the air governor and signals the unloader valve to charge the line to the compressor to stop pumping.

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Customer reply replied 3 years ago
its possiable the dryer is bad I have already changed the governor
Technician: Mike Mcmillan, Shop Foreman/Triage Tech replied 3 years ago

Yes, it is a possibility.

Mike Mcmillan
Mike Mcmillan, Shop Foreman/Triage Tech
Category: Medium and Heavy Trucks
Satisfied Customers: 6,440
Experience: Volvo/Mack Master Tech, Certified with Cummins, Eaton, GM, Hino, Detroit Diesel
Verified
Mike Mcmillan and 87 other Medium and Heavy Trucks Specialists are ready to help you
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Customer reply replied 3 years ago
I'll take on off a test truck and try it
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