a/c issues 88T

[cjones55555]

Morning all,
I have a 88 T that is fairly stock. I ran into A/C issues. The system has a full charge of R12. There is a 10A fuse on the passenger kick that keeps blowing everytime I turn the A/C on, keeping the compressor from kicking in.

As you look down on the engine, there are two schrader valves below the turbo. I disconnected the low pressure switch. Oreilly Auto Parts sell these valve/switches cheap, around $10. I'd like to replace it to see if that is the cause of my fuse blowing.

My question is: How? There is a nut looking thing on the top and a bigger nut looking thing on the switch. I assume I put a wrench on the smaller one to keep it from moving and unscrew the larger one. Assumptions are a bitch and there is some rather expensive R12 at risk.

Any help?

Chris
88T Auto
cjones55555@yahoo.com

 

[CPT Furious]

You are correct with the wrenching concept, however, you will lose all of your expensive R12 that way. The dealership assured me that it would not release pressure if I just pulled the switch to replace it, but they LIED. That was the last time I ever stepped into one...

 

[Supraholic]

sound like some sort of short circuit somewhere.. to blow fuse like that.. Check if there is continuity between any of the terminals of the pressure switch to the body of the car.

 

[cjones55555]

sound like some sort of short circuit somewhere.. to blow fuse like that.. Check if there is continuity between any of the terminals of the pressure switch to the body of the car.

Sounds good. Just disconnect the switch from the harness, touch a meter to any and all of the terminals and see if I have continuity. If I have continuity, there's a short somewhere. Right?

Thanks
Chris

 

[SPD TRP]

Looks like that 10A fuse circuit goes to the dual pressure switch and the ac amplifier which is located up behind the glove box in the general area of the ecu. I would unplug the dual pressure switch and see if the fuse blows, if so there is your problem, if not move to the amplifier, unplug it and see if fuse blows. Not sure of ac will even turn on with out the amplifier plugged in. Something to try and lets hope it is the dual pressure switch.

Just changed the condensor fan pressure switch, had to take down pipe out to get wrenches in there.

Wayne

 

[cjones55555]

Looks like that 10A fuse circuit goes to the dual pressure switch and the ac amplifier which is located up behind the glove box in the general area of the ecu. I would unplug the dual pressure switch and see if the fuse blows, if so there is your problem, if not move to the amplifier, unplug it and see if fuse blows. Not sure of ac will even turn on with out the amplifier plugged in. Something to try and lets hope it is the dual pressure switch.

Just changed the condensor fan pressure switch, had to take down pipe out to get wrenches in there.

Wayne

I unplugged one of the switches and I'm not blowing fuses. I'm at work and when I did this all I really wanted to see was if I blew a fuse. I didn't check to see if the A/C was working.

So that told me the problem is either in the switch or a short between the switch and the fuse. I was hoping it was the switch. I'm willing to replace the switch. my only problem with that is fear of losing freon.(R12 aka the expensive shit I have to get my bro-in-law to purchase for me)

I was told this switch was connected to a schrader (sp?) valve and removing it would not release the freon. Then in a reply to this tread someone said they lost all their freon when they removed the switch. I'm a little lost.

Thanks
Chris
88T Auto

 

[Supraholic]

If you unscrew the any of the pressure switch, you will loose freon.. no shrader valve there... check in
http://www.cygnusx1.net/supra/library/TSRM/d/D_27.html

for the wiring diagram for the A/C 10amp fuse.. trace the wiring diagram and see where the shorts could happen.. i wouldnt pull the swiches just yet.. because R12 being expensive...

 

[cjones55555]

A great many cars, both older and newer than the MKIII, have schrader valves under AC switches but I honestly don't know if ours do. I kind of doubt it knowing how adverse Toyota is to them.

There is no need to pull the switch unless it tests bad. A few moments with an ohm meter is all you need. For your symptom to happen the switch would gave to be shorted to it's body so that's easy to check. If you do need to replace it the refrigerant can be recovered.

I have my home work to do. I will try to track down my short.

 

[cjones55555]

If you unscrew the any of the pressure switch, you will loose freon.. no shrader valve there... check in
http://www.cygnusx1.net/supra/library/TSRM/d/D_27.html

for the wiring diagram for the A/C 10amp fuse.. trace the wiring diagram and see where the shorts could happen.. i wouldnt pull the swiches just yet.. because R12 being expensive...

Thanks. cygnusx1 is ( I believe ) for a 91 model and the 88 is different. That does not mean the wiring diagram for this fuse isn't the same, just I have run into issue in the past.

What your post does tell me is to leave that damn switch alone until I exhaust other options.

Thanks for all your help.
Chris
88T Auto