I have a 1991 240 that has had the R134A conversion done. Just got the car and been fixing little stuff. Down to the A/C now. The compressor turns on for a few seconds then goes off few seconds then back on few seconds. Just cycles like it is lowon freon. Hooked up the gauge to the low side you get from Walmart and it showed a little low. So added some freon to it. This did not seem to fix the problem. When the compressor is on you can feal a significant cooling of the air. However, with the compressor cycling it does not seem much eficient. Any ideas what would cause it to cycle like this?

Thanks.

 

OK. I played with the A/C more last night. Shorted the pressure switch to keep the compressor engaged. Low behold the freon level drops to below acceptable levels. Add freon the unit starts working a lot better. Still need to add more freon was real low. However the unit does not cycle as much any more. Lesson learned: Be sure the compressor is engaged for at least one minute to get a valid pressure reading.

Now off to other problems...

 

glad you got it to work! thanks for the info for future readers!

~jon