The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - AC high pressure cut out switch needed or not?

**hatzie** · 06-08-2013, 01:15 PM

The big alternator post on the back is power out (hot) to the battery. It's usually marked BATT.

The light green wire is hot when AC is selected and maybe defrost. It runs from the heater/AC controls to the low pressure cutoff switch. If the AC is charged then the LPCO switch is closed and power runs through it to the dark green wire that's directly tied to the compressor clutch.
I believe the H series compressor clutch has a short ground wire that runs to the engine or accessory brackets. There are no switches in the ground wire and it shouldn't be tied to the alternator BATT terminal.

06-08-2013, 01:15 PM	#24
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 5,021	Re: AC high pressure cut out switch needed or not? The big alternator post on the back is power out (hot) to the battery. It's usually marked BATT. The light green wire is hot when AC is selected and maybe defrost. It runs from the heater/AC controls to the low pressure cutoff switch. If the AC is charged then the LPCO switch is closed and power runs through it to the dark green wire that's directly tied to the compressor clutch. I believe the H series compressor clutch has a short ground wire that runs to the engine or accessory brackets. There are no switches in the ground wire and it shouldn't be tied to the alternator BATT terminal. Attached Images __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 06-08-2013 at 01:38 PM.