[W126 Coupe] Expansion valve theory:

[Richard Hogarth]

In my experience;
The expansion valve is a pressure device, not a temp. device. 
The expansion valve has a sensing line that  is attached to the suction side
of the ac compressor in some way. 
The expansion valve senses the pressure at the suction of the ac compressor
and modulates flow to maintain the pressure at the compressor suction.
 Therefore your initial question is important. What is the static pressure
of the system?
 
I'm 2 hours from houston,
where are you in texas?
 
axlehead at bellsouth.net

  _____  

From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Nathan Goodlet
Sent: Saturday, August 13, 2005 6:40 PM
To: Mercedes Coupes Mailing Lists
Subject: Re: [W126 Coupe] YOU'VE GOT TO GET SOME GUAGES AND LEAK DETECTOR


Yeah yeah I've got gauges, somewhere.
I also understand very well the AC system conceptually.
There is no real need for gauges to tell me I am not making high pressure,
or the high side would be hot 
Question is what causes the expansion valve to open and close? This pix
shows what appeears to be a thermocouple. .
. 
I've got liquid in the system that could not be liquid at less than
somewhere between 80 and 125 psi. I'm not too sure of the static pressure at
this point, I believe the blend favors the 70 psi at room temp component.
Course Texas hasn't seen 70 during daylight hours lately.
Problem is nothing is frosting up, or heating up significantly right now. 
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