Working on fixing a long list of problems on my 79 300D. I want to get my A/C going. Here's what I have so far.(Excellent thread regarding this)

Aux water pump was disconnected. I want to trouble shoot off the car to make sure it worksl

Defrost button of control panel works and fan blows air.

A/C switch does nothing when turned on.

Where do I start?

I believe, if there's no refrigerant in the system, the pressure switch won't make up, and it won't allow the AC compressor to engage. Do you have gauges to check? York compressor, right?

'77 300D, 363k mi

You have the servo system I believe. If you search on my username and 'servo manual', I posted a link to the manual for the servo system which has troubleshooting procedures.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13