Info on AC !!
Thread Starter
Senior Member
Joined: Jan 2005
Posts: 314
Likes: 1
From: Bryson City NC
93 300SE Rauch "Smoke"
Info on AC !!
I am looking for some info on replacing the Ac expansion valve on the firewall of my E420! I am gettin a negative or vacuum on the low side. The compressor is running so I must getting some pressure in the system. I have a new drier and pressure switch on order. I bought a set of gauges and from what I have read if you get a very low or negative reading it indicates a bad or stuck expansion valve and it is not running cool! I can see the valve on the firewall looks fairly easy to get to but I need some tips on replacement! Thanks
Smokie
Smokie
MBWorld Fanatic!
Joined: Dec 2006
Posts: 1,042
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
I am looking for some info on replacing the Ac expansion valve on the firewall of my E420! I am gettin a negative or vacuum on the low side. The compressor is running so I must getting some pressure in the system. I have a new drier and pressure switch on order. I bought a set of gauges and from what I have read if you get a very low or negative reading it indicates a bad or stuck expansion valve and it is not running cool! I can see the valve on the firewall looks fairly easy to get to but I need some tips on replacement! Thanks
Smokie
Smokie
You only have half of the equation. What is the pressure on the high side? With an outside air temp of 80°F, the high side should be approx. 124-158 PSI, or about 20-35° above outside air temp (I pasted a link to a TP chart).
If the high side is also low, the system is short of refrigerant. If the high side is equal to or slightly higher than the outside temp, then I would say the expansion valve is stuck shut or has a bad element.
http://assets.fluke.com/appnotes/ele...r/1265816_.pdf
Last edited by shdoug; Sep 6, 2007 at 11:26 PM.
