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Old 05-08-2013, 12:30 AM   #1
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Default A/C Issues

Hey guys,

My A/C works for 10 minutes(actually feels cold) and then my 10 amp fuse in the passenger side kick panel keeps popping. I don't know what is causing it and quite frankly don't know much about A/C systems. I know it still has R12 in it and will be more than happy to convert it once I have a working system first.

So I took my car to a local car repair shop and of course got the bad news. They said the wiring to the clutch is shorting out and that I need a new compressor b/c they don't sell them separately. $460 for the compressor/$720 installed. I am not really looking to spend that kind of cash on this car right now.

I am a decent backyard auto mechanic type guy who has recently completed a successful head gasket replacement on this vehicle and does most of my work DIY style. It's an 87 turbo in mint condition with 100k miles. One of the cleanest mkIII's I've seen.

Am I up the creek on this one or are there some natural steps I can take to get to the bottom of this without burning a hole in my wallet?

Thanks in advance.
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Old 05-19-2013, 01:46 AM   #2
Busted Knuckles
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Rockauto.com has compressor clutches for as little as 50 bucks!

However, you need a puller to properly remove the clutch IIRC from the TSRM.
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Old 05-19-2013, 12:49 PM   #3
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I'm wondering, if you replace the fuse as soon as it blows & switch back on straight away does the fuse blow again straight away or does it take another 10mins to blow?

I ask this because if the fuse takes another 10min then the clutch windings or a bad connection could be drawing too much current causing the fuse to heat up & eventually blow, but if it blows straight away then more likely there's something being affected by heat/cold and shorting out.

If you suspect high current draw not dead short then you can measure it using a multimeter with it's probes in place of a fuse, and maybe also compare resistance readings between the clutch windings on your car & one that's known good. Also you could perhaps go through the connections & grounds for the AC clutch anyway and just make sure they're all clean & wiring isn't chafed/corroded.

If you suspect a dead short then you could also use the multimeter (but don't try to measure amps!), this time by using the AC until it blows the fuse & then checking resistance in the clutch windings & through other areas of wiring, and also check for shorts to ground in the supply wiring.

I suppose the clutch windings could be at fault but I have to say I've never experienced it on any vehicle before, I'd have to say it's more likely a wiring/connection problem & therefore easier/cheaper to fix. But a session with the multimeter will tell you more anyway. HTH

EDIT-: Here's the TSRM section on testing the clutch windings, there's the specs for the winding resistance values http://www.cygnusx1.net/Supra/Librar...ection=AC&P=22

Also on the next few pages are details on removing/installing compressor and dismantling the clutch. Perhaps (and I don't know how much it'd cost) you could take the windings to an electric motor specialist if they're bad & get it rewound for cheaper than buying a clutch? Or if you're like me (broke & just like fixing stuff for the love of it) you could even look into rewinding it yourself...
Best of luck

Another EDIT-: Here's the part of the TEWD http://www.cygnusx1.net/Supra/Librar....aspx?S=D&P=30 showing the wire from the 10a A/C fuse. It's the v/r (violet?/red) wire at the top, it runs from the fuse to a plug where it goes to the pressure switch and the A/C amplifier, from there it becomes a y/g (yellow/green) from the pressure switch & a l/w (blue/white) from the amplifier, which plug together & send a y/g (yellow/green to the relay & then an l (blue) from relay to clutch. If the clutch Ohms out OK then these are the connections/wires to check next...
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Last edited by MA70-3.0GT; 05-19-2013 at 01:17 PM.
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Old 05-20-2013, 01:32 PM   #4
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I have a used compressor which i suspect to be good. If you are interested let me know.
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