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Old 06-18-2003, 04:07 PM
Posts: n/a
90 300se a/c try this one tech masters!

Greetings all!!!
I will explain what I have done first. My compressor started to leak. So I decided to get a new compressor and while the desire to stay with r-12, I changed all the hoses, condenser, R+D, pressure and temp switches all from Mercedes Benz. I have replaced the high and low fan relays too! The only thing I did not touch was the expansion valve and evap core.

My problem is two fold! When I am in the car and turn the "a/c" on everything seems very nice....cold etc etc. I just never see the compressor kick off. Now I have done the adjustments to the clutch so that when I disconnect the pressure switch I see the clutch disengage. So I rule out the over tighten clutch. Could this be a problem of the MAS unit not letting it go electronically?
The second problem and I have seen this from several posts is that the aux fan never comes on until the temp gauge is around 110 degrees. I agree that they will come on at around 110 degrees when the a/c is not on for the sake of bringing the temperature down for the engine.
But they must come on for the a/c system at an early point. For example in stop and go traffic you need air to pass through the condenser so that you get ample of cool air for the passenger.
My concern is that while traveling and forcing air to move though the condenser I great artic cold air. Now if I put 12v direct and make the aux fan come on I get great cold air at standstill. As an experiment and safety in mind, I want to wiring up a direct 12v to the aux fan (switched) while in downtown or traffic for manual testing So again is this all controlled by the MAS control unit? I read Steve Brotherton's article and was just wondering.
Thank you all for this wonderful forum and the people who join to make it happen!
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