[JustAnN55]

I’ve got a 2016 535i xdrive. On the first hot day of the summer, I noticed the vents would not blow cold air even with AC button illuminated. Checked under the hood and and the compressor wouldn’t engage. Tried to do a recharge and it wouldn’t take any refrigerant (makes sense as compressor is not engaging). Fast forward about a month, the car had to go to the body shop to repair damage from a shopping cart. The owner evacuated the system at no cost and even tried to recharge it with the same issue; car wouldn’t take the charge. Now we’re here. 90° days, no AC. And no ideas. My simple brain says compressor is locked up. But my pragmatic brain says that’s too easy. Fixing the car isn’t so much the issue as I’m cable of that part myself. But I don’t wanna just start throwing parts at it without knowing the problem. I did have the car checked and the only HVAC code that’s shows is that the compressor is shutdown due to negative pressure (no refrigerant). So my big thing is, how do I get refrigerant in the system if the compressor won’t engage because there’s no refrigerant? I know I could technically bypass the low pressure switch to force the compressor to engage (if it even will) but it’s a 4 pin connector and I don’t know which to jump. And if I’m not mistaken one of them should be a 5v lead that could potentially brick ECU if i mess it up. Any answers that may lead in the right direction would be greatly appreciated.

[Cvx5832]

You can charge a system without the compressor engaged, at least enough to get it above the compressor engagement threshold, where it can then take in the rest of the amount.

I also don't believe the compressor just quit. It's an input somewhere that's telling it not to.

[Hoa]

Evac the system and see if there is any leak. The needle must stay without movement for 30 minutes to ensure it is good. Typically if you are low on refrigerant, it is leaking somewhere. Most common places are condenser or compressor. Once confirmed that there is no leak, do not release that vacuum air. With that, you can pump in at least enough to engage the compressor. If compressor still won’t kick on, try to manually engage it by injecting a signal to the compressor directly. If that still doesn’t work, compressor is bad. If it does work, you have electrical issue which will require you to trace the wire.

[JustAnN55]

Originally Posted by Hoa

Evac the system and see if there is any leak. The needle must stay without movement for 30 minutes to ensure it is good. Typically if you are low on refrigerant, it is leaking somewhere. Most common places are condenser or compressor. Once confirmed that there is no leak, do not release that vacuum air. With that, you can pump in at least enough to engage the compressor. If compressor still won’t kick on, try to manually engage it by injecting a signal to the compressor directly. If that still doesn’t work, compressor is bad. If it does work, you have electrical issue which will require you to trace the wire.

Originally Posted by Cvx5832

You can charge a system without the compressor engaged, at least enough to get it above the compressor engagement threshold, where it can then take in the rest of the amount.

I also don't believe the compressor just quit. It's an input somewhere that's telling it not to.

Update. The system did take Freon. So I now have new codes. Which to me are pointing to an issue with the IHKA itself. Obviously not 100% sure my research is finding that it seems to be a communication issue. I very much appreciate the responses. This is the first time I’ve ever had AC issues with any car I’ve owned, and it feels defeating not just being able to diagnose it.