Strange a/c problem on '86 300E
 

Greetings All,

Perhaps someone can shed some light on this unusual a/c problem I have with the wife's car. I thought perhaps I was low on freon, and maybe I was but the compressor kicked in fine and ran constantly, but no cool air out of any vents at all. Did not matter what fan selector speed I chose the results were the same. No cool air output. I felt the lines coming out of the compressor and one was too hot to keep a hand on while the other wasn't cool or cold but ambient temp. I thought behaps the monovalve was over riding my call for cool, but wouldn't the output air temp be hotter that just ambient and the temp of the output line of the compressor be cool or even cold to the touch? I was using the sight glass as my gauge for reciever fullness, and maybe I shouldn't do that, should I? If the sightglass is pretty much free of bubbles, isn't the charge pretty well at it's full mark? Any input on this strange happening will be more than welcomed. I don't want to keep wasting this pricey R-12 on a problem that will require dumping the system to resolve.

Charles

Come on guys,

Help me out on this one. I know there is a wealth of knowledge just waiting to be tapped into and even more logical opinions.

Charles

Not a pro, but I'll throw in my 2 cents.

Your compressor turns on and runs constantly? I take that to mean you see the compressor clutch engage and turn and it keeps turning....never cycles off??

If the clutch is engaging and activating the compressor and it's not ever cycling off, then I'd say the temp sensor on/in the evaporator is never seeing anything near 32F. However, if this were a low charge issue, I'd expect the receiver-dryer pressure switch to cycle the system off in order to save the compressor.

The sight glass is certainly useful, but...

Whether the system is cycling or not, you need to have a competent pro hook up some R-12 gauges.
The low pressure side could be reading low or high and/or the high pressure side could be doing the same thing. The gauge readings can tell a good tech what's going on.

The receiver-dryer sight glass is not the final word in my opinion. This test should not break the bank. The fix may be a different story.

I would suggest you go to:

http://www.ackits.com/cgi-bin/ultimatebb.cgi

and post your question. Chances are you will get a reply from a professional automobile a/c service technician that will be of significant assistance.

Hope this helps and good luck!

Perhaps it could be something with the expansion valve? That is weird indeed. Maybe there is no freon in the system? and the sensor on the reciever drier is bad, and telling the compressor there is.