Hello,
I've got a 91 240 and just recharged the system, but the compressor cycles on for around 3-4sec and then back off for 8-10sec.
Coolingseems fine, but my concern is the rapid cycling of the compressor>?

It's been converted to 134 and also had a replacement compressorin the past by previous out of state owner's shop.
Any clues I can look for to solve the cycling issue?

UPDATED:
Just completed a road test. The cycling seems more rapid when at highway speeds..?

The car is in really great shape at 125k.

Thanks
Hope everyone is doing well.

 

Hey guys i have a simliar problem yet i have NO ac
mine cycles ON for 1 second and then off for 3
any ideas on the problem?

 

Maybe it is overfilled? This makes for very little room in the evaporator.

 

Is this normal? I have a similar problem, recently recharged w/134a after repair. Mine does not cycle at idle (ie runs fine), but cycles every 3-5 seconds at speeds over ~30 mph. Maybe overfilled? What would low side psi be for the system (91 740 base, BTW)?

Thanks

 

740SkiWagon you probably have a blocked system at the orifice tube or your pressure is low.



MyDaughters740

Low side should be in the 20 to 45 psi range. the high and low side should be at the same psi when the system is off and the engine cool. Also your compressor sounds about right. is the system cooling?

 

Beardog

I might be higher than 45, maybe in the 55 range. Probably drain off some pressure? Yes, it is cooling, but not as much as I'd like.

 

try cleaning the evaporater in front of the radiator, and then finding the condenser and cleaning that grill as well. you might be able to access this by removing the blower.

Also when your charging the system, you need to run theengine at 2500 rpm.

 

is the pressure reading for the car not running and the a/c off and cooled to ambient temperature?

 

Pressure is a/c running at idle, ~88 deg F outside.

 

MyDaughters740

if you can check the high side and the low side before you run the engine. the system should equalize and the pressure should be about equal to the ambient temperature (ie 80psi= 80 degrees F)If there are no blockages in the system. IF the pressure is lower then the ambient temp, then the system is low in pressure. other then that, right now, I would suggest that you try cleaning the condenser and the evaporater. The condenser is in front of the radiator, and the evaporater is under the dash near the blower moter.


also try running the system at 2500rpm and see if the pressure fluctuates between 20and 45psi. this isaround the normal points for the compressor to shut off and come back on.