91 4.9L - Need A/C Wiring Diagram

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Jun 25, 2018 | 09:44 AM

1991F250OH

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91 4.9L - Need A/C Wiring Diagram

I'm trying to troubleshoot a no-power condition at compressor clutch. Have a low/high pressure circuit continuity (w/LP switch bypassed) but not sure what else may be there (WOT relay?). Just replaced PCM so I don't think that's an issue but if someone also has a PCM pin diagram it would also be appreciated. Thanks.

Jun 25, 2018 | 12:27 PM

subford

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From: Easton,Ks

Here is one for a 1990 and a 1991 should be the same or close to it.

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Again 1990 and a 1991 should be the same or close to it.
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Jul 5, 2018 | 07:54 AM

1991F250OH

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Problem SOLVED - Appear that previous owner replaced the '91 A/C compressor and hoses with a later model (92-95) which included a HPCO switch. I suppose it would have worked except the LP/HP switches were never connected to the compressor circuit because the harness the guy used had the wrong male end C104 connector. Quick trip to local pick-n-pull and a splice job of the correct connector got the clutch working again, however, it looks like the compressor is probably bad as it began smoking as soon as I got the clutch to engage.