AC Compressor Clutch Not Getting Power

[sapote]

I'm asking because when I just tried it I didn't hear jack or squat from either valve. So at least I think I know now why the clutch isn't engaging. Now I just have to figure out where the leak is coming from. Any suggestions on how to diagnose this would be greatly appreciated. Thanks...

If the Freon already leaked out, then maybe just use compressed air to pressurize the system then listen for leaking sound and set the connection joints with soapy water. Are you going to evacuate the system down to some millimeter of mercury column vac (I pulled the vacuum of my home AC system down to the level of air plane flying at 30,000 feet) and charge it up with Freon yourself?

[BMWE46M3]

I really like the compressed air idea. Assuming I find the leak and replace the part then I will just take it in to a shop for a proper charge.

Regarding the compressed air method, can I simply add the air directly into the low or high side Schrader valves? I don't have any refrigerant gauges but will pick some up if necessary. Any instructions on this method would be appreciated. And yes, I did search for online videos but from the ones I saw every method included injecting the compressed air into the gauge manifold and since I don't have this, I'm wondering about directly injecting into the Schrader valves. Thanks...

[Cubieman]

That does sound like a great idea, just don't over pressurize the system. You could probably find the adapters needed at auto parts and/hardware store to get your compressor hooked up to the schrader valve.

[BMWE46M3]

Do I pressurize the valve located in the back of the engine or the one behind the passenger headlight?

[sapote]

Do I pressurize the valve located in the back of the engine or the one behind the passenger headlight?

I believe the valve near the fire wall is on the low side and for charging the refrigerant. The valve on the other line close to compressor is the high side.
The low side can take to 50 psi, and the high side can be 300 psi.

Using compressed air is not the best way to detect very small leak, but it is useful for relative large leak. For very slow leak, a very sensitive vacuum gauge is needed. I had done with vac pump that pull down to 100 micron mercury (for reference, ambient pressure at sea level is around 29 inches mercury column) , and wait for 10 minutes to see if the pressure rise up too fast or not. The pressure will rise even if no leak as there is some air molecules inside the system. Then fill the system with Nitrogen gas and then evacuate again to clean out the last few moisture and air molecules. Did this 3 times before charging with refrigerant.

[BMWE46M3]

Thank you…

[TropicalM3]

The evaporator is a common failure on these cars, I suspect you may need to replace that.

[BMWE46M3]

Thanks for letting me know. I plan to take a look when I get a chance to remove the front bumper.

[Shonky]

Thanks for letting me know. I plan to take a look when I get a chance to remove the front bumper.

Evaporator core is in the dash. Quite a bit of work to get it out. Local generic AC shop near me didn't even want to do mine (might have a slow leak)

[BMWE46M3]

Crap that’s right. I was thinking the condenser. So did you end up doing it yourself?

[Shonky]

Crap that’s right. I was thinking the condenser. So did you end up doing it yourself?

I haven't done it yet. I have had to have recharged twice in about 3 or 4 years so it's a super slow leak. At $150 a go to recharge every couple of years vs ripping the whole dash out I'm on the fence as whether I should do it. I also don't know for sure if that's the problem. They couldn't find any of UV dye evidence last time so the assumption was it leaked at the evaporator core.

[BMWE46M3]

Sound logic.

[Cubieman]

Kind of off topic but do our vehicles have known heater core issues? Specifically leaking.

I ask as when mine "went out" on another vehicle it dropped coolant all over the passenger footwear area which was quite the mess.


I wondered if one was to do an evap if you may as well do the heater core while your in there.