I am new to the forum. Just bought a 2001 ML320 and two days ago, I had the A/C running, so the next morning, I switched from cold to warm air. Ever since then, regardless if I have it on cold or hot it blows nothing but hot air. I took it in to the shop to recharge A/C and it is working fine but still the same problem. The mechanic thinks it's the temp control motor to the tune of 1006.00 to fix....HELP !!! any suggestion from the group? Checked all fuses and they are all good.

 

We just bought a 1999 ML320 5 days ago. My wife is German and fell in love with a super clean ML320. One previous owner. It appears very well taken care of. All the records checked out. But it does have 127,000 miles. We paid $6,500. Two days after we bought it the air-conditioner stopped working. Since then it works intermittently. When it does come on it works fine and is nice and cold. It seems to be tied to the temperature. When it gets hot enough, after all the occupants have been sufficiently cooked, the thing finally comes on. The dealer said they will diagnosis the cause for free next week. I've read horror stories of $1,000 temperature control units needing to be replaced.
This is our first Mercedes. I fear we may have made a bad choice. From what I have read it appears that the ML320s have design and quality control issues particularly with the electronics and drive train. I take good care of my vehicles and stay on top of maintenance. I don't mind fixing things once. But I get very annoyed when the same items continue to cause problems due to faulty engineering. My wife loves the vehicle. I just hope this isn't the start of many expensive repairs.

 

I took the car to an independent mercedes repair shop, and right away, i had to pay for diagnostic and a new re circulation pump e-box that cost me 417.00 so far and still not fix the A/C issue. I was told that it might be the temp control box and it will run about 700.00 and up
I am afraid the ML320 is the step child vehicle of mercedes.

 

I don't trust the Mercedes dealer anymore so I ignored their offer to diagnosis the cause of the A/C issue for free and then "talk over" the cost of the repair. Screw them. They have lost my business forever. Instead I took the car to my local mechanic in whom I have great faith. Unfortunately, he is an expert in Fords and not Mercedes. I also own a Ford F250 diesel. For $100 he checked out the entire vehicle and said that overall it appeared to be in very good shape. That's the good news.
He could not check the transmission fluids. Apparently it requires special Mercedes tools. He also said that the engine has 12 spark plugs, two per cylinder, that may require a special tool to remove. Anyway, he believes that the cause of the air-conditioner issue is a leaking seal on the compressor. He priced the job with labor at slightly over $1,000. He is an honest guy but I sensed he was uncomfortable working on Mercedes.
Before I committed to the repair I spoke to some local Mercedes owners. They told me about a local independent father and son shop that has been repairing Mercedes for over 40 years. Thus they are experts in Mercedes and can handle any job. I called them and they were super knowledgable about Mercedes issues in general and ML quirks in particular. The son told me not to panic, that perhaps they could just replace the seal or a hose. He said that MLs are very nice vehicles and reliable once you sort them out and stay on top of maintenance. Anyway they are going to look at it next Wednesday. I feel better already. These guys love Mercedes and really seem to know what they are doing.