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Old 08-26-2007, 05:16 PM
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hispassion hispassion is offline
I Want A 1935 500K!
Join Date: Nov 2006
Location: Peoria, Arizona
Posts: 112
Thanks for the input guys. However, the compressor is NOT cutting off!

The MAS control module has no affect (as I understand it) on climate control except to cut off the compressor in the event of a failure.

In the Phoenix summer heat, there really isn't any way to tell if it's heated air or just ambient air. Heck, the cold water faucets here spew hot water from July through September.

Since the compressor is not cutting off and the vent temp comes up almost instantly, I'm now led to believe something is failing in the A/C system. Compressor maybe? With my limited experience in domestic refrigeration, compressors (I think) have reed valves and maybe there's a weak reed valve. Would this cause the high rpm heat up issue?

With this thought in mind, I'm surmising this scenario...

If it can't compress (above a certain RPM) and the freon is allowed to pressurize the evap, this could essentially heat soak the evap making it seem like the heater comes on or the heat ducts are open.

Something to note; when the heat does rush in, there are no plenum door noises, just a change in temperature.

I welcome your thoughts, ideas and diagnosis.

Michael B.
1992 300CE - 157kMi (my white beauty)
1992 300CE - 220kMi (sold)
1990 300E - 189kMi (sold)
1990 300SL - 102kMi (salvaged parts available)
1986 300E - 230kMi (salvaged parts available)

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