A/C Problem on a 124 1986 300E
 

Hi All,

Need your guys help. On my 86 300E 124 chassis I had my a/c shop check the car and said they found no problems, freon was full, no leaks.

I noticed that when I reach a stop light the vents stop blowing cold air, they continue blow but it blow cold to warm then hot. But once I get moving again the cold air is back. Also when I reach a stop not only the vents start blowing hot air the engine temp gets higher.

What can cause this?

Thanks
GP

Are your auxiliary fans working?
 

Or the main fan?

I'd agree with JH -- if the aux fan isn't running, and the visco clutch is weak, the temp will get too high and the compressor will shut off until the high side temp comes down. This is to prevent stalling from high pressure, and blowing the high side AC hoses (I've done it, because the aux fan wasn't working on the 220D).

Check the fuse for the aux fan, and make sure it runs when you unplug and cross the temp sensor wires on the receiver dryer, and that when you unplug the temp sensor in the middle of the head that the aux fan runs.

Chances are the visco clutch is empty, too.


Peter

If the system has been converted to 134 this would happen and be normal behavior. If system still 12 then above replies apply.

Have a great day,

Hi,

Forgot to mention the system has been converted to R134

Thx

Larry:

R134a usually just gives reduced cooling at idle -- it will blow cool air, not cold, and the fan will stay on high. This was my experience with the 300TE in Cleveland -- temp in the 80s, six people in the car, and stop and go driving with a bad visco clutch. Wasn't hot, just not cold.

Hot air would be something else, like the compressor cutting out.

My brother says ALL German cars, R134a or R12, have limited cooling capacity at idle -- his new Jetta TDI does the same thing. Has to do with a 6000 rpm rev limit on the engines, I think, so they run the compressor slower than US or Japanese cars.

Good thing, I'd hate to burn one up trying to pass someone.....

Peter

Rotate the temp dial back and forth a tiny bit when it acts up -- the 300TE has a tendency to stick on hot or cold, and I have to wriggle the dial to get a decent temp. I've heard this is loose pins on the circuit board, but I've not dived in yet to fix or find another one.

Peter