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I have a weird problem with the AC on my 940 turbo wagon. When I'm driving at normal speeds, it works great. When I'm at a stoplight or just idling somewhere, it's also great - since about 15 seconds into being stopped, the ECU activates the low-speed fan and the fan will stay on indefinitely as long as the AC and engine are on. The problem occurs when I'm in heavy traffic, going slow but not completely stopped. At this point, the ECU doesn't have the idle signal, so it won't turn on the fan - and I'm not going fast enough for the condenser to do its job. At this point, system pressure rises so quickly that the purple high pressure switch shuts the system down. I know that the brown and grey pressure switches should be turning the fan on at this point, but they don't. I've replaced both of them, and still no dice.
The weird thing is that I've jumped both the brown and grey connections, and they power up the fan just like they're supposed to, even with the engine off - so I know the circuit and the relay are good. The compressor is new as of last year, and doesn't have a high-temp shutdown switch, so that's also ruled out.
My other 940, a year older, doesn't have the ECU idle feature, and the grey pressure switch cuts in and out just as it should. Needless to say, the cooling is much better in that one in slow traffic!
So I'm guessing that the ECU is somehow overriding the functionality of both pressure switches. Is this possible? Anyone know more details about these little differences in AC wiring between model years?
Thanks in advance
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