AC Compressor Clutch Not Getting Power

[BMWE46M3]

So my AC clutch stopped engaging last week, and I can't figure out what else to do with the exception of taking it in to a shop. I first disconnected the plug feeding into the compressor and checked to see if it was getting any power when the ac system was "on". There was no power. So I checked the connector itself and the wiring. The wire sheathing was cracked in one location so I suspected maybe the wire itself was damaged so I cut the wire before the damaged sheathing and once again looked for power but this time on the bare wire (not the connector) and still got jack. So I then checked every fuse and relay switch associated with the AC system including the relays behind the glove box. Still nothing... I then removed the HVAC control unit and removed the circuit boards and looked for any signs of failure (i.e. broken solder points, blown resisters, etc.) but everything looked fine. I have also checked the system using my Schwaben (AKA Foxwell) scanner along with INPA but there are no errors. However, I also recognize these two tools are limited. I was able to command the electric auxiliary fan to operate with the software. I also had the system charged less than a year ago.

With all of this being said, can anyone think of anything else I can check before I take it in for "professional help". Thanks...

[Shonky]

Clutch won't be engaged if it detects no pressure. May be as simple as gas leaked. Was it perhaps getting less cold recently? Hear a hissing noise in the centre of the dash. Left side (US drivers side) colder than right? All of those indicate low gas.

[BMWE46M3]

Thanks for the reply. I will check out the pressure.

[Shonky]

Not sure but you might be able to read via INPA or something like DeepOBD that might give you idea what's wrong if there are no codes otherwise.

[BMWE46M3]

Unfortunately INPA was useless, and I don't have DeepOBD.

[Arith2]

If the pressure is fine, start with checking the pressure switch. Has your instrument cluster been acting up in any way?

[BMWE46M3]

No, the instrument cluster has been fine. Why do you ask?

Anyone have recommendations for a set of pressure gauges?

[Cubieman]

Harbor Freight for your gauges and vacuum pump if you decide to charge it yourself.

I don't really recommend the use of those DIY AC "cans" you get at the auto parts store but the gauge off one of those will give you an idea if you have a charge at least.

[Arith2]

No, the instrument cluster has been fine. Why do you ask?

Anyone have recommendations for a set of pressure gauges?

Power to the clutch runs through the cluster as it is the gateway of the car. Do you have the wiring diagram?

[BMWE46M3]

Harbor Freight for your gauges and vacuum pump if you decide to charge it yourself.

I don't really recommend the use of those DIY AC "cans" you get at the auto parts store but the gauge off one of those will give you an idea if you have a charge at least.

thanks....

[BMWE46M3]

Power to the clutch runs through the cluster as it is the gateway of the car. Do you have the wiring diagram?

I have a Bentley manual so I suspect there is one in there. So when you're talking about "cluster", I assume you mean the HVAC control unit, correct? I've had no problem with it. And like I mentioned in the beginning, I removed it and dismantled it to examine the pair of circuit boards but everything looks fine. And if I didn't say so above, the light for the AC (the snowflake) illuminates when depressed and I was also able to detect when it was depressed using my scan too. Unfortunately the compressor clutch line is getting no signal/power.

I'll order a set of gauges and vacuum pump and check things out and will report back.

Thanks everyone...

[BMWE46M3]

If I depress either of the Schrader valves on the high side or low side of the system when the car is off should I hear refrigerant hissing out?

[BMWE46M3]

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...

[Cubieman]

You would have to charge with freon and put UV dye into the system to find the leak unless it is quite obvious.

[BMWE46M3]

That’s what I thought. I’ll try and pick up some gauges and vacuum pump this week. Thanks…