'99 ML430 - Air Conditioning inop
 

Hi,

Yesterday while we were on a trip I noticed that the driver-side stop-light wasn't working. Not wanting to drive several hundred miles without it I bought a GE P21W bulb at the gas station and installed it. On the way home I noticed that the a/c was not working. (It was last week.)

When I reached home I checked the underhood fusebox to see if fuse 44 had blown (A/c fans). It was ok. On a short trip this morning none of the instruments and stats lights worked. When I returned from that trip I opened the fusebox to make sure I hadn't disturbed anything, closed it up again and started the car. Now all the instruments and status lights work but the air is still inop.

Anyone care to venture a guess what's going on?

Jim

A/C compressor operation is controlled by a computer called the AAM.
That computer must receive a signal from the controls inside the car & then evaluate the a/c system pressure & at that point activate the compressor.

Computer controlled means computer diagnosis.

Thanks very much MB Doc. Can you answer a few more questions?

Where is the AAM located?

Does installing a new one require a Dealership?

Could my installing that stop-light bulb have caused this? (Is the AAM that sensitive?)

Was there ever a recall on the AAM? (I ask because I vaguely rememebr reading that there was a recall of some type, but I'm not sure.)




Thanks.

Yes AAM on 1998-99 ML's require special dealer coding.
Bolts to the bottom of the fuse box.

Never recalled. Many 1998 models had a service update. First 22,000.
Light bulb couldn't cause that problem.

Thanks for replying MB Doc. One last thing. Can independent MB service facilities usually do the install??


And that's the last question........

Depends on their level of scanner quality.

Might need refrigerant (R134)
 

If the light on the AC button comes on but the compressor doesn't, try getting a $20 DIY refrigerant recharging kit from Autozone or Advance and try recharging. I did that several times and it will get the AC working (until it all leaks out again) ! It takes about 5 mins and unless you have a really bad leak it should get you going again.

Thanks. I'll give that a try!

Jim