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I over-filled my AC - how do I reverse?

Old 06-13-2010, 12:26 AM
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Originally Posted by dr bob View Post
Turns out that the later S4+ 928 has enough extra condenser and fan capacity to work with R-134a OK, so long as the fans ALWAYS work. Net performance is comparable up until somewhere north of 95║F ambient at engine idle.
The manual cars have a taller condenser due to no auto-box cooler (about 3" from memory?), so presumably a greater refrigerant-condensing capacity even?

I use r134a (no choice here in Australia) - I haven't figured out yet why the fans in my '87 always run with AC on, and in my '89 they don't.

I guess I should have a closer look at the over/under pressure switches and make sure they're working correctly. Memory says that if you bridge the pins on the top one (over-pressure), the fans will run all the time, so I may have a short inside the switch.

I need a new condenser for my '89 (car is currently in pieces, so I pinched the condenser out of it to fix the '87's leaky system earlier this year) - my plan is to track down a suitable aftermarket parallel-flow condenser to fit, further improving the efficiency of the system.
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Old 06-13-2010, 02:43 AM
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The fans on the S4+ cars work from AC system pressure as determined at the transducer that sits on the top of that little tubing manifold next to the drier. The controller by the passenger's seat doe the dirty work with that signal only when the AC button is pressed and maybe only when the compressor relay is engaged. I need to go look at the schematics again to be sure. The expected operation is the same between the '87 and the '89 models I think. On mine, the fans start immediately on AC button press with the key in position 2 (engine run), even if the engine is not yet actually started.
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