christianmond6

Mercedes ML Air Conditioning Failure

My 2009 Mercedes ML, gasoline engine, with about 114960 km has an A/C system that's stopped working. The air conditioning doesn't activate, so there's no cooling. An error is recorded. Could undervoltage be the problem?

The air conditioning system in a 2009 Mercedes ML stopped working, with an error recorded, possibly due to undervoltage. Potential causes include issues with the A/C system relay switch or the belt tensioner, which can affect voltage levels. A visual inspection of the belt tensioner is recommended, but a full inspection by a qualified technician is advised to diagnose electrical issues accurately. The problem was confirmed to be undervoltage, resolved by replacing a faulty part.

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4 comment(s)

That sounds like an issue I had with my ML. A/C failure is never fun. Did you check the A/C system relay switch? Also, have you looked at the belt tensioner? A bad belt tensioner can cause undervoltage issues that affect the HVAC system. What error codes are stored?

Thanks, I haven't checked the relay switch or the belt tensioner yet. Would a visual inspection of the belt tensioner be enough for a first check? I'll get the error codes and share them.

A visual inspection of the belt tensioner is a good start. Look for wear, damage, or misalignment. But, a full inspection might need special tools to check the tension properly. Since undervoltage is suspected, and you have error codes, I'd suggest seeing a qualified technician. They can do a full check of the electrical and air conditioning systems. For me, it was an electrical issue causing the A/C to cut out sometimes.

Thanks for the help. I took your advice and saw a technician for a full check. It turned out undervoltage was the cause. Replacing a bad part and some labor cost 240€.

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MERCEDES

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