Reinstalled A/C blowing fuse—-Where to look???

[BillyMoore]

So I bought the A/C conversion kit to reinstall the factory A/C in my 91 GT convertible. Everything fit perfectly and after I got it charged up with 134 and oil the fuse for the compressor circuit keeps blowing. I isolated it to the low pressure wiring on the accumulator… the fuse does not blow until I plug the accumulator in. It will blow with the compressor unplugged. Anybody have any ideas on where to look? I’m guessing there is a dead short somewhere. The A/C had been removed from this car when I bought it. I installed everything new but the evaporator inside the car.

When I have everything connected and a new fuse installed and turn the A/C on the clutch doesn’t appear to try to engage and the volt gauge drops way down and the engine briefly lugs down from the alternator load then the fuse pops within a second or two…

I’m at a loss and not the best electrical troubleshooter. Any advice?

 

[General karthief]

Does the ac clutch engage?

 

[revhead347]

I assume you are talking about the cycle switch on the accumulator/drier that controls compressor function. Try bypassing the pigtail with a paper clip and see if it blows.

Kurt

 

[90sickfox]

Also check the WOT relay. On the earlier 87 to 89 cars it's located on the passenger fender apron by where the MAF is located. Not sure about the 91. I've had a couple cars that had issues with the wiring at that relay. Like Kurt said, if you jump the switch out it should cut the compressor on if the control panel is swit hed to AC and the key is on. If there's an issue with the AC compressor harness it can also cause the fuse to blow. There's a diode in the harness where the black / yellow stripe wire runs from the compressor towards the drivers strut tower.

Also, unplug the compressor and see if the fuse blows with everything else connected. Wouldn't be the first time a new part was bad.

 

[BillyMoore]

I tried to jump the switch on the accumulator to see if the compressor clutch would lock in but it did not and it did blow the fuse. Also, fuse blows with the compressor disconnected. I will look for the WOT relay and check that.

 

[Mustang5L5]

Here’s the wiring. My guess, the wires on the WOT relay have dry rotted and are shorting to ground.

I believe in 1991 the WOT relay is bolted to the fender under the MAF

Unplug the WOT relay and plug the low pressure switch in and the try another fuse and see if it pops. If it doesn’t, the issue lies from the WOT relay (or it’s wiring) downstream to the compressor.

My guess the wiring on the wot relay plug is a bit brittle.

 

[BillyMoore]

I got side tracked…I checked the WOT relay wiring and changed the Relay, no change. I failed to mention in earlier posts that I had the dash pulled back to change the heater core so I’m wondering if I should pull that back to look for a pinched wire…I’m not sure where to look but this acts like a major short to ground. When I plug everything in and turn the A/C on it puts such a load on the electrical system the engine slightly lugs down and the volt meter pins low. Any more advise out there?

 

[Mustang5L5]

Remove the WOT relay, put a new fuse in and turn the ac on. It won’t engage, but if the fuse pops that would suggest your short lines ahead of the wot relay on the wiring diagram, which includes all the dash wiring that might be pinched somewhee.

Edit: actually the low pressure cutoff is further up the line that the wot relay. You can just unplug that first, and then try to power up with a fuse. If it doesn’t pop. Unplug the wot relay and plug the low pressure switch and try again

The idea is to try and confirm what is good and what is not. If there is a pinched wire ahead of the low pressure switch, then the fuse should pop when you start car and engage the ac as it send 12v down that wire to the compressor.