94coupe

Sudden onset of AC blowing warm air in all phases of operation including normal driving and idling.
For a start, I am uncertain if aux fans are operating normally.
( After driving in warm weather for 30 minutes aux fans are not running when car is sitting still, idling.
They do run on high under same conditions if I disconnect the 2-pin lead from the thermostat )

I have pulled and and reinserted aux fan fuse, both aux fan relays, and relay fuse, with no change.
Considering that AC issue may be related to aux fan issue.

Looking to troubleshoot further.

Any help appreciated.

ohollenbeck

Sounds more like the compressor not kicking in, or much worse, the dreaded evaporator leak.
I have a 94 E420 that all of a sudden started doing the same thing, ok did the first quick thing by getting a couple of cans of freon, and charging it up.
It worked for 1 day, then got hot again, more Freon, 1 more day.
OK, now I feel there is a leak, so how to find it, used the Freon with the green die this time,
The green die was coming out from under the center of the dash, actually the HVAC box.
Inside the HVAC box are the control flaps and the evaporator.
After some homework, bad evaporators on 94 and 95s are common, they have copper and alum mixed, and the dissimilar metals eventually react, corrode and leak.
If so, the best solution is replace the evaporator with a new all aluminum part, what I did and now works fine for 5 years.
The only problem is that you need to remove the entire dash board to get access to the evaporator, not for the faint of heart.
I paid to have mine replaced, about $1800 5 years ago, and that was the cheapest I could find. The part is only $200 or so, it's really all a pain in the *** labor job.
And while its all open, replace all the vacuum pods, some of them are probably bad already, and they will all go sooner or later, and the fresh air flap pod is NLA.
It would be nice if your evaporator was already replaced, and something simpler was wrong, but a/c not working on a 94-95 is highly suspicious for a bad evaporator, The video below is not for a 124, but it's the same process... enjoy


Good Luck...

94coupe

Thanks for the reply. I went through the dreaded evaporator replacement a number of years ago, but I don't know if they used an aluminum replacement.
I suppose it could always recur, but I am going to do further troubleshooting.

I was suspicious that if the aux fans were not kicking on properly, they might be affecting the AC operation.

Shadow5501

ohollenbeck

That's great you've had the evap done already, Shadows comments are more in line now. I'd start with the compressor 1st...

Good Luck...