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Hello. This is my first time trying to setup link ecu on an e36 retaining its AC. On the stock circular bmw x20 connector, i found that pin 5 is (ac pressure switch). I am wondering how this pin should be connected to the link ecu. Is it a 5v signal from the ecu or a digital or analog input to the ecu?
also regarding pin 4 in the x20 connector (ac compressor control), is this low side switched by the ecu to engage the compressor?
Ahmed,
Common options to figure that out would be to test with a multimeter before ECU replacement, or get the factory service manual which should explain how both items work. I like to have the factory manual because it provides other useful information as well.
I don't know that switch offhand, but if it's only a single wire, and it's called a switch, I would see what's on the wire when system pressure is low. If it's NC, then maybe the signal becomes ground when pressure is high for example, but you'd have to test to determine that.
On the plus side because it's just an AC pressure switch, you can operate the AC, monitor the switch behavior and then figure this out without much trouble.
The AC control pin might be a bit risky to just send power or ground on, so I'd measure the stock behavior or get the manual to be on the safe side.
