My AC doesn't stay cold after about 10 minutes. I was trying to do the diagnostics using the AC control display.
I get the numbers on the the drivers side, but the passenger side is blank.
Is there a bulb that could be burned out? Any suggestions?


It's a 1999 E320 with 271k miles.

If you have the same controls as a 97, there is only one bulb and that is for night viewing. When you are in normal mode, is the right side visible?

As long as the compressor stays engaged after 10 min, the most likely cause is a expansion valve sticking closed. My 97 SL320 was like that. The valve can stick open freezing the evaporator but air flow will also drop.

The next possibility is the variable displacement compressor going to minimum displacement.

I looked again in the only thing visible is the letter C.
A couple days last the week air-conditioning didn't stop like it normally does. You might be right about the valve sticking.
Where was it located and how do I check it?

The expansion valve is near the brake booster where the 2 AC lines go through the firewall.

The valves are in the $ 25 range for aftermarket and I just change old valves anytime the system is empty to avoid future problems. Access can be difficult though but removal consists of one nut for the hose , two allen / torx bolts and the valve comes off.

With a properly operating valve, the suction hose ( the larger one ) will be cold as it exits the valve, if it is hot and the system has a proper charge the valve is sticking shut.

Make sure the compressor isn't stopping though. And check to see if the heater valve is opening when it shouldn't. There was a recent thread where this happened and one side of the dash vents were hot and the other cold during AC operation. http://www.peachparts.com/shopforum/tech-help/145624-hot-cold-air-same-time-c280.html

Thanks. I'll check and see if the suction hose is cold.