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Old 06-05-2019, 07:02 PM   #2
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,471
 

2003 L-Series 3.0L Sedan
Default Re: Transmisson Backlash and AC Clutch

There are cars with driveline slop but not to the extent of what you're experiencing. Are you sure its a driveline problem? Broken/worn engine mount(s)? Engine controls can produce similar symptoms. With 120k miles, what's the history of maintenance and parts replaced?

How do you know the ac clutch coil is open and the reason for the ac fuse blowing? The ac diode is used to absorb arcing in the ac relay contacts when ac is turned off. Diodes tend to short and blow fuses when ac is turned on. Look for this diode in the engine fuse panel, remove it and measure it for resistance with a multimeter. A diode acts as a choke for electrical voltage when a magnetic field collapses and generates a reverse voltage. This voltage can arc across the ac relay and burn contacts. Most ac diode failures occurs by creating a short and acts as a wire. A shorted diode usually blows the ac fuse when ac is turned on. A diode will measure resistance in one direction and when multimeter probes are reversed, resistance is higher. A faulty diode that's internally shorted will measure the same resistance in both directions like a wire.

Clutch coils have a very low resistance, between 2-3 ohms. Clutch coils have a built in thermal fuse to open when overheated above 450F, a possibility from a slipping clutch (rare). An internal short in the coil would either blow the main ac fuse or the internal thermal fuse. You can measure coil resistance.

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