'85 C20 350/400, A/C- Thought I saw a similar post but didn't find it. I just plugged in a multi wire plug to a relay on my firewall and now I have a only low fan speed (in all run modes), but no A/C . At least it's some progress over nothing at all. A/C worked great before the swap after a R134A conversion. I've got power to a pair of light green wires on one end of a coupling that also has a single dark green that goes to the A/C clutch and apparently he accumulator/drier. but no power. There's a multi wire plug on the black plastic fan(?) box and all colors show power with a test light. Looks like no power at to the clutch is part of the problem. I don't think that is related to having only a low speed on the fan. Since all work was in the engine compartment and fuses are ALL good, the problem must be under the hood, electrical, and maybe vacuum?. Second photo shows light and (dead end)dark greens' plug, the first shows a dark green wire (by left fender. near booster) that doesn't seem connected to anything. Should those two connect? Wiring diagrams I have for an 85 don't show any light green wire and only one dk grn from "panel lps 5 amp" fuse to "Panel & interior lamps control switch" (WTF?), not to A/C fuse at all. IDK what "convenience center" is. Don't know where "ACCotroller is at. Haven't seen any "gra" wire at all. Is BLK a ground? It has no power.