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5.0L (1979-1995) MustangTechnical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.
You didn't list the year,make,model & engine unfortunately,but if this is a 86-93 Foxbody you're working on,its likely a bad clutch coil,ac wot cutoff relay or one of the wires is open on the relay.The relay/plug has a slot on the side of it that slides over a metal tab/bracket (screwed to the inner fender apron) on the passenger fender under/ beside the maf sensor.Pin 30 & 87A on the relay are normally closed which allows 12v to continue on to the ac clutch coil which energizes the coil & makes the compressor engage.When the ecu detects wot,it grounds the relay through ecu pin 54 and this causes the normally closed relay contacts to open, which cuts off 12v to the ac clutch coil & the compressor stops running.Thats possibly/ likely why both wire terminals at the ac clutch coil harness are currently showing as grounds.You can remove the relay from its harness plug,touch the meter leads to pins 30 & 87A with a multimeter. Check for continuity/ohms.The meter should read 1.0 ohm or less.If it reads higher,OL or infinite,the relay is defective.The following diagram may help with a visual of the circuit.Ignore the circled "break in circuit" item.Like stated above,pin 30 & 87A are normally closed with the relay off,so to understand how the relay/circuit works,visualize a line being drawn between pins 30 & 87A, meaning the contacts are closed (which would allow voltage to pass on to the ac clutch coil through the black/yellow wire) and then visualize it with no line meaning the contacts are open (which would prevent voltage from passing on to the clutch coil)
Last edited by wbrockstar; Feb 25, 2020 at 06:19 AM.