[Lear35A]

I have a troublesome clutch and I'll take any/all free advice. When I push the AC button on the dash, the 7.5amp AC fuse (#29) blows immediately. As a test I put in a 25 amp fuse, and the AC works...the clutch engages, and the system blows nice cold air. I just ran it this way for a minute, and the wire going to the clutch got hot. Obviously the clutch is drawing too much current, but it's not shorted out. How is this possible?



Awhile back I ordered from Zims (I think) a rebuilt clutch. I checked the resistance across this rebuilt one and my fuse blowing one, and they were exactly the same and, according to Zims, within spec. So I sent the rebuilt one back.



Any ideas? Maybe run it for very short periods with the 25 amp fuse to "loosen it up"?

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[mbardeen]

How about checking the wire? Perhaps there's an internal break or fray somewhere?

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[vliegwielolaf1234]

Bad wiring , is my guess . also bad connections would make a wire go hot or even melt and burn



The loosening up thing , i would say no , that would possibly set you on fire <img src="/forum/images/smilies/968/excl.png" class="smilie" alt="" /> <img src="/forum/images/smilies/968/excl.png" class="smilie" alt="" />

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[Lear35A]

I'm not against checking/replacing the wire. It comes from something called the air conditioning pressure switch. Anybody know what that looks like or where it is? From that switch it goes to relay G19 in the fuse box and then to the fuse #29. Unless I can locate that switch my troubleshooting has ground to a halt.

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[mbardeen]

The pressure switch, judging from what I can tell from the parts diagram, is connected to the system right next to the desiccator.



In this photo, the desiccator is the aluminum cylinder, and the pressure switch seems to be under the cooling hose.

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[Lear35A]

That's too easy. Thank you. I'll check this first thing tomorrow.

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[MB968]

[quote name='Lear35A' timestamp='1345146887' post='131111']

Obviously the clutch is drawing too much current, but it's not shorted out. How is this possible?



[/quote]



Most ohm meters only put a small voltage across whatever is being checked. With a full 12v across the clutch, you could cause a ground fault that didn't show up with the ohm meter. If you put 12v directly across the clutch (not through any of the other wiring) and check the current flow with an ammeter. If it is above the spec. then the clutch is likely shorting internally with the higher applied voltage.

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[DaveN]

If it turns out your re manufactured clutch is the issue I have a brand new one you might want to try. I ordered it and never needed it

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[Lear35A]

I know this doesn't make a lot of sense, but it is exactly what happened. I let the AC run for about a minute at a time with a 25amp fuse. I i did this about four or five 4times over the course of a couple of days. Just now I tried a test. I put in a 15 amp fuse, and it didn't blow. So I put in a 10 amp fuse, and it didn't blow. So I tried the 7.5 amp fuse, and son of a gun it didn't blow either. I'm going to drive it now for awhile and see if things stay good. This is about the best outcome I could ask for. Now if the crack down the middle of the windshield will repair itself....

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