My snow flake lights up on the climate control but nothing happens. There's no voltage going to the ac clutch or any change in the vehicles's idle. I'm thinking it might be the dme.

Did you connect gauges to the high and low side ports and determine what the system pressure is without the compressor engaged? If the system is low, the DME will not engage the compressor.

I actually replaced the pressure switch so I had the system recovered, vacuumed, and properly recharged. Still nothing...blows ice cold once I send 12v to activate the clutch. Also installed new electric fan, which had stopped working...no the fan run on high all the time. I also replaced the coolant temperature sensor. I'm definitely not overheating. Any ideas?

I used scanner1.4 and found a code/fault for high pressure. ( I believe it was code 15). That's*after I replaced the high pressure switch. Fan seems to be working correctly now.

If the DME and AC system is giving a High Pressure fault that could be the reason why the fan is running all the time and on high. Could also be the reason why the compressor is not engaging because of a high pressure condition.

Do you think it likely I got a defective pressure switch or that the dme is toast. When I bought the truck it had a 12v run to the compressor..and all the connectors were left plugged in. Maybe the dme shorted out??

Reason why someone ran 12 volts to the compressor is because they were too cheap to fix it right. I suppose they had a switch to turn on the compressor. Lucky that the system didn't blow up.

Don't think the DME is fried if you have a high side trouble code and the compressor is not turning on. The DME is doing what it was designed/program to do and that is to shut power to the compressor if the high side is too high.

Did you buy a genuine BMW part or an aftermarket part?

I bought it from pelican parts and it has the bmw stamp on it. However, it was smaller than the original ( socket size needed to remove/install). The part number was not bmw's, I believe it was OEM brand.

I checked the pressure with the compressor OFF and I got 85psi on both the high and low side. Still the compressor wasn't getting any signal to turn on..not even for a few seconds. I'm starting to think I got a defective or wrong pressure sensor.