500SEL Air Conditioner not working
 

While doing a search for similar problems I found this post.


I have a 92 500SEL and in the instruction manual it mentions a Diagnosis Mode for the Automatic Climate Control. What does this do? How do you get into it. The reason I ask is today the temperature outside was in the 80's. My wife had been driving my car and when I got in and turned on the A/C the air conditioner did not work. The red light came on on the Auto button and also on the EC button and refresh button but the unit would not push out any air. I turned the car off and tried again but that did not reset it. I waited to later on tonight and the outside temperature went down to 70. I turned the dial button to Auto and pressed the Auto button, this time the blower came on and the unit proceeded to cool the interior. Can anyone think of why the unit would not work in higher outside temperature? I also see in the manual that when the temperature is high outside that "the system engages the recirculated air mode". Could there be someting not engaging correctly based on the high ambient temperature?


I am having the same problem, I have checked the compressor and it is engaging properly any clues. My car is a 1993 500SEL

Thanks guys

Cardude

A/C Diag Codes
 

read the 'stuff' on my page, #15 for A/C. I believe it's the same techique for the '93.

Thanks,

I will give it a shot tonite.


Cardude

Mixed results,

I ran the first test just fine. I wonder how many bars are really required (of coolant pressure) to cool the car. But anyway I could not get the second test to run properly I keep getting E0 00 as if the codes had been erased.

Any other clues, compressor still engages



Cardude

Normal operation
 

for my car, as an example, goes like this:
1) the evaporator sensor (#5) cycles between 36F and 43F with the engine at 1500 rpm.
2) the refrigerant pressure (#6) cycles between 8 to about 14 or so. Initially, it will start from about 5 or 6 and then build as the A/C operates. Also if it's a warm/hot day, the readings will vary abit.

If your readouts are the same as mine, then there's nothing wrong with your A/C! It could be the pushbutton's contact on the panel.

If #5 reads low, that might explain why the A/C did not turn on. Not enough pressure to activate the switch.

for my car, as an example, goes like this:
1) the evaporator sensor (#5) cycles between 36F and 43F with the engine at 1500 rpm.
2) the refrigerant pressure (#6) cycles between 8 to about 14 or so. Initially, it will start from about 5 or 6 and then build as the A/C operates. Also if it's a warm/hot day, the readings will vary abit.

If your readouts are the same as mine, then there's nothing wrong with your A/C! It could be the pushbutton's contact on the panel.

If #5 reads low, that might explain why the A/C did not turn on. Not enough pressure to activate the switch.


My #5 reads very high at 77-88F

Sounds a little high maybe I'm a little low on coolant?


Cardude

What's #6 read?

#6 55F

Oops! Meant #7?

#7 05

The car was not running while performing the test. The test was run with the switch turned to the on position.


Cardude

Need to run the test with the car idleing and A/C on. Since you said that the temp (#6) is around 77F, you probably will see that the coolant pressure is low.

With the car running,

#5 53F
#6 70F
#7 03/04
#8 16/25
#9 07
#16 R


Cardude


It seems low. Is it safe to add it myself.


What would you consider normal?

If you add some R134a (sure that all '93 MB used R134a), it will probably just leak out. I guess it depends how big the leak is???

Probably should add some leak detector while refilling the A/C so you can see where it is going.

But make sure the cart used R134a. In one of your posts, you mentioned a '92. They, most likely used R12.

Ok, so it does seem low. The car is a 93 500SEL, I was quoting the only post I could find while doing a search on this topic in the very first post. I will double check to see if it is a 134a. I sure hope its not the evaporator. Can the dye be purchased by a DIYer.


Thanks for all your help on this topic,


Cardude