A/C blows only hot air after temp sensor & instrument cluster replacement

[gigtime]

I've got a 2003 Z4 roadster with 2.5 engine.

Late last year, I hit a black garbage back in the middle of a darkened I-10. It took out the protective cover below the bumper. I removed all the loose plastic and taped up a hanging wire I later discovered was the ambient temp sensor.

Recently, the car died on me. It looked like a bad fuel pump but it turned out it was actually just out of gas, the gauge was stuck. BMW of Austin replaced the instrument cluster.

They also told me the ambient temp sensor had been dragging on the ground and was damaged. They wanted a fortune to repair it because they needed to replace all the missing parts to have a place to mount it.

Without the sensor, the car shows the temp as -40F and the AC would only blow hot air. Doing a search here, I found that's normal when the sensor is gone or wiring is damaged and it prevents the A/C compressor from coming on.

I picked up the sensor today and replaced it, fastening it near the horn with a zip tie until I'm ready to replace the whole bumper. I saw posts here warning me that it would take about 20 min of driving for the sensor to start to work but mine showed 100 F right away (it was prob 95 here today) but the A/C continues to only blow hot air. I drove for 20 min or so and checked different settings Max, auto, etc. but nothing but hot air.

I realize there could be a leak, bad compressor or it might just need to be charged but before I have all that diagnosed, am I missing anything? I've read about a safety mode when the system detects a problem but am not sure how to 'reset' the system if that's the problem. Just spent a fortune on repairs and am hoping there's something I'm just overlooking.

Any suggestions?

[AVolkov]

Try to disconnect the battery.

Once I hit a bump (the speed was very low, but the car hit it with subframe) and all cluster died for 1-2 seconds, after that the AC blowed only hot/warm air. The battery disconnection and moving the temp control a few time from cold to hot solved the case.

[gigtime]

Originally Posted by AVolkov

Try to disconnect the battery.

Once I hit a bump (the speed was very low, but the car hit it with subframe) and all cluster died for 1-2 seconds, after that the AC blowed only hot/warm air. The battery disconnection and moving the temp control a few time from cold to hot solved the case.

Did you just disconnect the positive terminal or both + and - ? I disconnected the positive terminal, waited a minute or so and reconnected it. Tried different settings on the A/C including moving the temp controls but same result. Nothing but hot air.

[HaiDef]

more freon?

[gigtime]

Originally Posted by Hdoan86

more freon?

This wasn't something that came on gradually and, as I understand it, when the refrigerant is low, the compressor tends to constantly cycle on and off. That's not happening.

The ambient temp sensor coming off was the prime suspect but sometimes replacing the instrument panel can trigger a problem so they dealer is going to reset it on Monday. They also recommended the battery disconnect but that didn't do the trick.

We'll check freon then, too. I'd love for it to just be in need of a charge or have a small leak. After dropping $1400 on it this week, I don't have to replace a compressor and condenser and it's tough to go without A/C when it's 95-101 every day.