1994 E320 AC woes - MBWorld.org Forums

Mar 20, 2018 | 10:35 AM

94coupe

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e320 coupe

1994 E320 AC woes

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.

Mar 20, 2018 | 11:52 PM

ohollenbeck

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From: North East

04 E500, 00 SL500, 99 SL500, 94 E420, 92 500E, 92 500E, 92 300CE, 06 Lexus GX470

Quote:

Originally Posted by 94coupe

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...

Last edited by ohollenbeck; Mar 20, 2018 at 11:56 PM.

Mar 21, 2018 | 04:41 AM

94coupe

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e320 coupe

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.

Mar 21, 2018 | 08:14 AM

Shadow5501

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Joined: Nov 2009

Posts: 724

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Car free at the moment

On the 124, no low speed aux fans is more likely a symptom of low refrigerant / non-functional compressor than a cause of no cooling. If the compressor and refrigerant charge were ok, you would have good cooling at driving speed, as there is plenty of airflow over the condenser regardless whether the aus fans are operating.
Next step is to determine if the compressor engages when ac is switched on. You should be able to hear it click and see whether the clutch begins turning. If compressor engages, check for low refrigerant charge or blockage in the system. If compressor does not engage, also check for low refrigerant charge as a cause, but could also be electrical issue, bad compressor clutch coil, excess compressor clutch gap, etc.