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step cover mac valve leak

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99' Windsor

My step cover mac vale leaks from the exhaust port when the pressure @ 120 PSI.

After shutting down the rig the pressure drops (from the leak) and @ 60 PSI it stops.

The mac valve is a 4 port unit 45A-AA2-DDCA-1BA. I've been told the it can be replaced with

a Humphrey Valve D1052 from NWRV Supply. Has anyone had experience with this valve.

If so, I need a hookup diagram.  As far as I can tell, it doesn't have an exhaust port.  Do I need 

that port.


Dan Petrow

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I don't have the part number from when I replaced mine as I'm not at the coach. However, it's pretty easy to replace. It should be located on the passenger side firewall. CAUTION!!! There are two ways to access the valve; one from underneath and the other through the generator compartment. DO NOT ACCESS IT FROM UNDERNEATH!  There are two wires connected to it, two screws to hold it in place and two air lines running to it. When you disconnect the air lines, your coach will DROP in about a second and a half. If you're underneath, that's where you will stay until the coroner arrives.  The air lines are a press fit meaning you press IN on the collar while pulling on the line and it'll pop right off. Replacement is the reverse of removal...Dennis

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I'll go further than Dennis and say to NEVER get under a vehicle with air suspension, or one on hydraulic jacks, without a MECHANICAL support capable of supporting the coach in place.

ANYTHING that causes an air or hydraulic pressure loss will drop the coach SUDDENLY, to about 4" from the ground.  Not enough space for me.

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Thanks for your input, the mac valve is located on the firewall above the genset.

No worries about crawling under the rig.  Still having a hard time locating the mac valve (is it discontinued?

Pulled all the hoses off and sprayed ports.  Don't know if it helped Has anyone had experience with substituting a Humphery Valve.

Again The mac valve is a 4 port unit 45A-AA2-DDCA-1BA.   And the Humphrey Valve D1052 from NWRV Supply.



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I don't know about the Humphrey valve but would think it needs to relieve the opposite pressure somehow. Have you looked at MAC 45A-AA2-DFEA-1BA as a possibility? It is used in some Monaco/HR as OEM.  ~$65

Often times the valve can be taken apart and cleaned unless the coil is burned. I have done it on a tag valve years ago and still works. If you have moisture in the line, it won't last. Aluminum does not like it. The leak stops at about 60 PSI because the pressure protection valve kicks in.

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