tanreddy

Hi folks,

I am newbie in here & please help! I have ML320 (2003)
My blower fans don't turn on & my A/C is blowing ambient air. To test & troubleshoot, I did the following Checked fuse F44 & is good. Removed relay K26 and it tested good. Using a multimeter connected to a ground, 30 & 86 on the relay showed 12V (i.e. they are getting power). Connected the multimeter to power & tested the relay base. 87 shows12V. Cranked the engine up & turned my A/C on & 85 doesn't show any voltage (i.e. no ground is being provided by the computer). I thought the problem is with either a climate control module OR AAM. I replaced my climate control module in the dash with a new one. That did not help. I bough a new AAM module & replaced the existing one and reconnected the wires.
Engine wouldn't start as the pins were not all the way in AAM. I corrected it. Engine cranks up. I still don't see the auxiliary fans starting & I don't see cool air. I see that the low pressure line doesn't cool as well.

Please help!

Dfixit1

The condenser fans get their signal from the ECU to come on when temp gets up to required and should likely be off when you start the engine then enguage when the temp rises. If the A/C is not cooling and you have replaced the AAM, I would check or have the 134a checked. My 2000 ML 320 calls for 1.7 lbs or 27.2 oz and that pressure is what the(on my SUV) Trinary switch needs to send the signal to the AAM Then back to to the compressor clutch to enguage. My best guess, with a replaced AAM is either low on freon or bad pressure/trinary

Dfixit1

Mercedes-Benz is very protective of their A/C compressors. The Aux or condenser fans get their signal through the ECU when the engine temp gets up to at least normal operating. Also the A/C freon HAS to be up near its required pressure to satisfy the pressure or trinary switch which ever you have. My 2000 ML requires 1.7 lbs or 27.1 oz of 134a. So having said all that. If it's not one of those items it could be the engine temp. sensor bad. it could be the ECU or or or at some point you may have to find an Indie shop or dealer{god forbid} that has a really good scanner and see what codes Moma Benz is throwing at you for messin round with her baby.
I just had a somewhat similar issue with mine, new AAM and all is good eccept my fans run any time the engine is on unless I pull the relay, I have also replaced and checked the #26 but it's just getting a continous signal. So I have a date with my Indie Guy 0n 7-1, I'm not sure but he may can reset the ECU so the fans work as they should and mate/program my key FOBs to the new AAM.
Let us know if you find out why yours is on the "Fritz" if you get It figured out