Hello Folks

1999 3500 Duallie Quad Cab SLT Laramie 2wd, Cummins Diesel

Is their any common issue with the air conditioner blowing the fuse? ie wiring etc?

I found the fuse burned and tried another one with instant results(burned it out to).

Heater and fan still work well. No other apparent electrical issues

Cheers

Peter

 

Rubbed wire on the AC clutch would be my guess. The harness would have to be traced to see where the wire may come in contact with some hard edges that may rub through.

 

Tested with wire disconnected at clutch connector, fuse good. Power at connector. Other pin at connector shows open/no ohms.

ohm'd the clutch and got 0.3ohms between the two leads in the connector. Although, no ground fault through either of the two leads on the clutch side.

Is this the sign of a faulty clutch? Why would it blow the fuse with no short/ground fault.

I couldn't find a diode anywhere as discussed in other threads.

 

Good question on the clutch.. Not sure what the correct resistance is on the clutch coil.

 

Service manual asks you to test it differently, they call for voltage between 11.5 and 12.5V at the clutch, and Amp reading must be between 2.0 and 3.9 Amps, at 4. Amps, replace the coil.

Working backwards, V/I=R, we theoretically should see between about 3 ohms and 6.25 Ohms to satisfy the conditions.

Running the calcs shows at .3 Ohms you would be drawing right at 40 Amps, which would blow your fuse immediately.

Now there could be other factors of which I am not taking into consideration, but if it were me, I would probably take a chance and replace the coil, unless someone else a bit more familiar with the system chimes in.

PS diode is there, usually shrink wrapped.......but I really don't think that is your issue.

Re-read the post, are you saying with the connector disconnected from the clutch it still blows the fuse?

 

If the fuse stays good with a/c on (calling for clutch engagement) and clutch unplugged change the clutch. .3 ohms is pretty close to a short circuit, coil windings probably melted together somehere internally. I'm not sure what parts are replaceable on the clutch/coil/etc or if you are better off with a new compressor.

 

All good information! Of course the math makes sense once you look at it. Seems like a short.

 

Thanks guys.

With the clutch harness disconnected at the compressor, the fuse stayed good.

It was the clutch coil internally shorted.

A clutch here was $340 + from the dealership.

A compressor here was (at my considerable discount"Lordco Auto Parts) $413

I got a NEW compressor from "autoaccompressors" from Florida off ebay and had it installed for about $30 more than the compressor alone would have cost me here. Total cost installed was about $442 CDN.

Thanks again guys, for all your insight.

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