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Discussion Starter · #1 · (Edited)
1986 Mustang 5.0 factory air I owned for 27 years.

My ac has been acting up it works on cold startup freon reads good, then when it cycles or the switch is turn off and back on the clutch doesn’t kick back in and has no volts at clutch. When working the cycle switch has 12.2v on both sides, the wire at the wot relay from cycle switch has 12.2v, the red computer power wire has 14.1v, the computer to wot trigger is what I not sure about it reads 9.6v, then clutch wire reads 12.2v. Then when not working only thing different it no volts to clutch black/yellow wire. I tried two new relays still samething. (All volts reading are from a power probe III). If I use the power probe to add 12v to clutch wire it kicks in when not working.

Anyone got any ideas?

Thanks Jerry
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you need to put a set of ac gauges on it to see what high and low pressure are doing. When engine is running and your AC is working, i bet you'll find that wire with 9.6v is showing ground. That's most likely the trigger wire from the ecu. It sounds to me like the ecu is not triggering the relay on. Did you check that relay when the engine was running and ac was on high?

 

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Discussion Starter · #3 · (Edited)
I think I traced it down to a bad ecm, the pin wire 54 had 9.6-10.2v. The clutch should be hot on the relay unless the ecm gounds it out to kill power. Just swapped in the original computer that was taken out for bad capacitors, that has been fixed and pin 54 now gets 14.1v just like pin 57 and all seem good but I need to drive it a few days to know for sure. Emc that was in the car is also showing signs that the three capacitors are leaking to And need to be replaced.

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