nlzmo400r

2013 ML350 gas with M276:

Wife says AC was working fine and then suddenly it stopped blowing cold yesterday. A/C light is flashing and will not stay illuminated if pressed.

checked codes and found 91e815 : Output for compressor has a malfunction, short to positive.

Pressure in system is good, I checked voltage at the clutch solenoid and saw 11.5v. Compressor spins easily by hand. Tried to apply battery voltage directly to clutch via battery - clutch doesn’t do anything.

Am I right in thinking the AC clutch is toast but the compressor is ok if it still spins freely?

Lastly, has anyone replaced the clutch without removing the compressor and evacuating the system?

mike919

I don't know anything about the A/C compressor on these, so not sure if the clutch should engage when voltage is applied. But your saying the compressor spins by hand, it seems like what your actually spinning is the disengaged clutch not the compressor itself

Terry WM

Hi
It is not uncommon for the clutch to fail, mine did twice.

I replaced the second one in car, fiddly but doable.

jimyj

It sounds like the AC clutch itself might be failing, especially since applying direct battery voltage didn’t activate it even though the compressor spins freely by hand. The short to positive indicated by code 91e815 suggests there could be an internal fault within the clutch solenoid, preventing it from engaging properly. Additionally, wiring issues such as a damaged harness or poor connections to the clutch solenoid could be causing insufficient power delivery, leading to the clutch not engaging. It’s also worth inspecting the ground connections for the AC system, as a compromised ground can disrupt the electrical flow needed for the clutch to operate. You should probably run a full system scan. There should be fault codes on at least one or more control modules related to this. You'll either need to take it to a mechanic, but if you want to figure this out yourself, then you'll need to get a full system scanner. The youcanic full system scanner is very good at diagnosing all systems, and there are other scan tools that can do this. Just be careful to use a full system scanner or you may scan the car and see no fault codes as some scanners can read all vehicle systems. youcanic can run an in-depth all system scan as well as diagnostics. I hope this helps, and feel free to reach out if you have more questions!