Air conditioner not working

[Meestahbig]

It's been awhile (2+ years) since my 2003 needed any repairs, but recently a bunch of stuff has gone wrong and I am tackling them - coolant and power steering fluid leaks resolved. Now onto my broken AC.

I've replaced the compressor before in 2016 and it's worked fine until now. I only have brief notes about the swap being pretty straightforward, but forgot a lot of the details.

I do see the belt running when I call for AC, so pretty sure the switch is OK. The system is holding pressure and has a full charge - so I don't think its been leaking bc it is now low.

Here are a few questions:
1) how can I rule out a bad temp switch and bad pressure switch?
2) I forgot how to test the continuity on my existing compressor
3) how to determine my compressor is actually dead and the cause before shelling out $300 on a new one.

Thanks.

[EODguy]

When you replaced the compressor did you replace the condenser?

Many times not doing so will slug it with oil and it kills it. Pressure wouldn't be affected in that case.

Don't ask how I know...

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[Bdc101]

Does your aux fan work? If it doesn't work, the AC will not turn on. Can be a blown fuse or a bad fan.

[X5chemist]

The clutch is a two wire plug, +/-. Check for power. Use a digital voltmeter across the compressor plug. 0 ohms means the clutch is fried.

Mine has a bad switch. I know because the fan does not turn on right away. Once the engine is hot, it doesn't matter. Engine cooling keeps the fan running. It's a bit annoying on hot days. I don't mind it for now. I start driving right away and cooling begins. I have not replaced the switch since the system has to be evacuated. I'd rather not disturb it until necessary. Once it's moving or the fan is running, temps go down to 42F!

If you have a 12V power source, you can actuate the clutch. Or use a bidirectional scanner. With the engine off and activation, you should hear the clutch engage. With the engine off, can you spin the compressor by hand? Likely, the clutch is worn out or slipping.

[Meestahbig]

I did some more checks. The clutch spins ok by hand. With the car on and the AC button pushed the clutch does spin with no issue, however there is no change to either the high or low side pressures, which are equal at near 60 psi. So the compressor is spinning but not doing anything. I'm going to assume the compressor is shot, but typically with my other HVAC the compressor dies and have no connectivity or it shorted out to ground and blowing the circuit.

[Effduration]

you may have figured it out - with a bad compressor -

BUT as already asked, is your Aux fan working ?

BTW- my aux fan failed...and rather than go with used or a new Genuine BMW fan, I went with Taiwan-made TYC fan for my E53 with lifetime warranty for 1/3 the price. I have been happy with it and would do it again if I had to ..

I checked, and TYC has been making electronic auto parts since the 60's...

[aureliusmax]

recently I found that clutch power pigtail connector screwed onto the body of the compressor was missing the insulation and shorting out against the body and not actuating the compressor clutch.