1989 740 GLE Air Conditioning Compressor Controller

I am having a problem with my air conditioner compressor only running for a
few seconds then turning off for 15 seconds or so then repeating. Because
of the short on cycle time, I don't get a lot of cooling. It doesn't make a
difference if I put the selector on Max air conditioning, Medium, or bilevel
air conditioning, it still cycles on for just a few seconds. Does the main
computer control the on/off cycle time or is there another control? I have
enough freon in the system and it seems to work ok except it just doesn't
cool much. Can I get a schematic for the air conditioning circuit somewhere
on the internet? Has anyone else had a similar problem? Thanks.

Dave

 

I would virtually guarentee you dont have a full charge of refrigerant with
these symptoms.


Tim..

 

I agree with Tim - those are classic symptoms of low charge.

In the '89 you have an R-12 system unless it has been converted to R-134a.
Ordinary people like us can't buy R-12 any more, but professionals have it
at a very dear price (since the production is prohibited in most of the
world now).

Mike

 

If I recall reading correctly, overcharging the system will also lead
to excessive cycling -- but lack of coolant is the most common cause.