BMW A/C Repair

I recently had to have the radiator & engine fan replaced in my 2000 BMW 328i (224,000 miles). Upon driving away from the mechanic, the a/c wouldn’t work - no cool air (worked prior to this). Returned immediately to mechanic. He checked relays, fuses, etc… but couldn’t get compressor to kick in. “Come back when we have more time to check it out.” Next morning, I noticed the readout on the exterior temp was -40 degrees F. Not in Houston, Texas! Temp was at least 75-80. As I drove on open road with no stops, temp rose. Aound 20-25 degrees, the compressor kicked in – cool air! Pressure held most of the time but occasionally would drop suddenly to sub zero temps. Compressor would kick off. But as I kept driving, temp reading would rise & at 20-25 degrees, a/c would work. In stop & go traffic, forget about it. Reading never reached correct exterior temp. What is the problem & how much to repair? NOT going back to this mechanic! Don’t trust him now due to other subsequent problems from radiator & fan repair. Will take up reimbursement of cost with him.

I don’t see a radiator fan replacement being the cause of this problem at all, BUT I could see the original faulty radiator fan as being the cause of an A/C problem seeing as how a non-working fan can be detrimental to the A/C system.

You also refer to “cool” air, which is not the same as “cold” air. So, problem exists and this problem likely existed before the fan replacement.

Without a schematic to look over, I cannot tell you what the problem is here but it seems to be that it’s a bit premature to blame the mechanic for this; especially on a car with 224k miles on it and a history of a radiator fan/AC problem.

Yes, your new problem is related to the radiator replacement. The exterior temperature sensor is mounted in front of the radiator. It must have been damaged, or the wiring to it damaged during the radiator replacement. It will have to be replaced or the wiring fixed. The climate control will not function correctly until this is fixed. It won’t even turn the compressor on if it thinks it is too cold.

So you don’t think that the temperature sensor could have been damaged by someone working where it is?

If you’re familiar with the BMW wiring setup then I defer to you. I’m not even saying the shop is not guilty of causing this problem; only that an 11 year old car with 224k miles on it could be reasonably expected to have problems due to aged electronics and corroded electrical wiring and connectors.

The OP says (quote) that they are “NOT going back to this mechanic!” It seems to me that the guy should be given an opportunity to really look the car over before whaling on him.
The OP is also looking for reimbursement on something that is not even known as to whether the shop is at fault or not.
If I were the shop I would not reimburse anyone based on a fix done by someone else who stated that I had screwed up because there is a lot of oneupmanship involved in the mechanic world. Many mechanics take a little delight in pointing the finger at other techs.

I do wonder how the A/C could have worked so well on an aged, high miles car considering the radiator fan was inoperative.
As far as I know, just about every car has safeguards to prevent compressor operation when the radiator cooling fan is inoperative. (high pressure cutout switch, thermal overload switches, etc.)

There is a TSB titled “outside temperature display is incorrect”. Unfortunately the file carries a “file not found” message. You should try and locate this TSB. TSB’s are called “Service Information” when dealing with BMW.