jwex2

My 99 320's A/C will not blow cold air on occasion. It happens about every 4th usage or less. Everything is reading correct on the diagnostic display except for the evap temp is not as low as during cooling . It is not above the ambient temp when not working so it appears that the compressor is not working. Although most of the time it works great. I had replaced the blower regulator to fix a fan problem . The numbers indicate that the evap temp unit is OK. The refrigerant is OK and the EC light operates and does not light when the malfunction occurs. The problem remedies itself after a couple trips.

Any thoughts on how to troubleshoot this. It is unpredictable enough that I cannot always pull over to diagnose or get to a shop when it is not working.

Any ideas? Is there a reset procedure to resolve temporarily if I really need the A/C

Redtallman

could be the valves . when u first start the car they are set open for heat when u cut on ac they suppose to shut off the water to heater core think they are call duo valve do a search i found it in the e 320 area sometimes they stick hope that help

neodoc

Try checking the sun sensor inside the rearview mirror housing. On mine, the A/C would not cool on hot days if left on Auto, and sometimes cut off cooling once it got started. The sun sensor was replaced and problem went away. Just my $0.02.