idafrank1

SL Air Conditioning Problem

Has anyone experienced A/C issues with an older SL? My 2003 Mercedes SL with a gasoline engine is blowing hot air. The A/C system doesn't switch on. I scanned it and there's an error stored, something about undervoltage. Could it be a refrigerant leak or a bad pressure sensor?

A 2003 Mercedes SL is experiencing air conditioning issues, blowing hot air and not switching on, with an error indicating undervoltage. Possible causes include a refrigerant leak or a faulty pressure sensor. However, after professional diagnosis, the problem was identified as a wiring issue causing undervoltage, which shut down the A/C compressor. Repairing the wiring resolved the issue, restoring the A/C system's functionality.

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4 comment(s)

Undervoltage? That's weird. I had a similar problem with my SL's air conditioning not cooling. I was convinced it was the AC relay or something in the A/C system itself. Did you check the refrigerant level? A small refrigerant leak can cause the pressure sensor to shut things down.

I haven't checked the refrigerant level directly. How would I do that? And where is the pressure sensor located? I'm not very familiar with the A/C system layout on this car.

Honestly, checking the refrigerant properly requires special tools. The pressure sensor is usually near the compressor. Given the undervoltage error you mentioned, and my experience, it's probably best to get it checked out by a workshop. They can diagnose it properly. Could save you money in the long run.

Thanks for the advice. Took it to a workshop, and you were right, it wasn't just a refrigerant leak. Turns out there was a wiring issue causing the undervoltage, which then shut down the A/C compressor as a safety measure. They fixed the wiring, and the A/C system is working perfectly now. Cost me 240€.

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