93 300D (124) - A/C won's stay running...

[svengruber]

A few days, for the first time ever, my A/C began to intermittently stop working. Specifically, the air blew cold for a few minutes until the car warmed up, and then the compressor kicks off and warm air follows. After a few minutes of pushing all the HVAC control buttons, I found that turning on the front defroster results in cold A/C coming through the defroster and side dash vents. If I cycle from the defroster back to normal A/C modes, the compressor kicks off and no A/C. If I start in the defroster mode though, I get normal hot air. I have worked under this approach for a few days to maintain A/C in these last hot summer days.

Again today, A/C worked for a few minutes upon startup and then shut down (no cold air, fan automatically went from high (auto mode) to low). Again, I switched over to defrost mode and had cold air for a few miles, and then it stopped producing cold air. No A/C no matter what setting today. Lastly, when under low engine speed crusing into the neighborhood, I again turned on the A/C to see what would happen and could feel the drag on the engine of the compressor kicking on and off, on and off, repeatedly every few seconds. I have since stopped using any of the HVAC system as I don't want to burn anything up.

I read some forums regarding issues with the auxiliary water pump drawing too much amperage and triggering similar results. I have unplugged the auxiliary pump with no luck...no cold A/C.

I replaced the KLIMA relay a few years ago when the A/C stopped working. That fixed the problem then and I have had no problems since.

It comes across that something (relay, switch) is getting overloaded and is causing the current issue, but otherwise I have no clue. Any thoughts or suggestions?