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Air pressure problems


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Hey guys, I have an 2001 Rd 688. Started it up today and I'm only building about 90 psi on the guage, but the low air buzzer isn't building any pressure at all. The green needle on the guage reads about 90psi. The orange needle reads 0 psi and obviously the buzzer is going off. I'm in Michigan, could it be frozen? Where do I start. I normally would call my buddy, but unfortunately Covid took him way to soon......

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The orange needle is for the secondary air system. Usually the low pressure indicator (buzzer) is tapped of the secondary system supply tank. There is a one way check valve at the inlet of the both primary and secondary tanks to prevent supply air coming from the compressor from flowing back into the compressor and/or air dryer and/or wet tank. It sounds like the check valve at the secondary tank is stuck or failed. 

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Sometimes the check valve will have a metal bracket around it and it says “check valve” or it’s a large elbow fitting with an arrow on it. 

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26 minutes ago, Onyx610 said:

That will do it, maybe replace the dryer cartridge too. 

Good call Ony ! This comment applys  To the newer vehicle's specially!  The magic transmissions and after treatment crap needs dri air to operate correctly We see more failures to the 7th injector dowser modules attributed to  water than almost any other failure on the after treatment setup ! and the stuff aint cheep!

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Let the truck build air pressure and stand outside of the truck and look to see where the air purges at. That’s where your air dryer is at and the cartridge is on top of it. 

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  • 4 weeks later...

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