The a/c on my 1984 TD is flakey as hell. First problem: The ccu turned on the blower, but only if I pushed the defrost button first. Then it stopped doing that and worked normally.
I had the car retrofitted to R134. The a/c ran ice cold for two weeks. It would cut in and out occasionally, but always came back. Then it went out for two days. Came back one morning. I checked the connections at the receiver dryer and found some corrosion. Cleaned them. A/c no longer works.
When the compressor clutch did come on, auxiliary fan didn't run.
Shorted the connections from lower switch on the receiver dryer. Heater pump came on. Shorted top two connections that should power the clutch, nothing. No voltage from either terminal to ground.
I understand there is an a/c relay somewhere that should provide power to the clutch. Where is it?
If I run 12 volts to the receiver dryer terminals, shouldn't the clutch come on regardless of the condition of the relay or the CCU?
Why isn't the auxiliary fan coming on? Where do I find those connections so I can test that with 12 volts directly?
Am I missing something?
Help. It's 98 degrees here and I am boiling in my otherwise terrific 300TD.
To make matters worse, my wife says,“It serves you right for fooling with those old cars,” while she tools around in her air conditioned Saab.

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Stage Wizards Lighting and sound designer
1981 SD 328,000
1985 300TD, 266,000
1984 300 TD, 267,000