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FINAL STAGE (final drive is differential) (archive)

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Posted by Chris B on August 11, 2001 at 02:30:56:

In Reply to: Sword ( Final Drive ) Repair posted by JarJar Binks on August 09, 2001 at 22:01:56:


Thought I'd throw in my 2 cents worth on this since I repaired my "sword" yesterday. Symptoms: heater fan would only work in the fully ON position.

Once I got the sword out I had a heck of a time getting all that ugly epoxy out of the way so I could unsolder the power MOSFET's for replacement. Power MOSFET's for anyone not electronically inclined, are devices whose current flow is dependent upon the voltage applied to them; as the voltage increases so does the current and hence the fan speed.

The sword assby is much bigger than I expected; a honking long piece of metal about a foot or so long to which a Printed Circuit Board is attached (PCB) , and about 3-5 inches wide... I was expecting something much smaller.

Used grinders and damaged the PCB traces a bit but I was able to rebuild them using short pieces of wire soldered across the damaged areas. I did not want to use big blobs of solder as that would risk future cracks on the board.

One thing different from one of the articles I scrounged up re the procedure; I did not have to remove the existing stand-offs (simply mounted the new MOSFET's on them; this means I only drilled the rivets out on the heat sink. After applying plenty of thermal compound ( heat sink grease ) to the tabs of the devices, I then simply drilled a couple of holes through the metal heat sink and the PCB through which I then mounted a couple of small bolts ( with thread sealer on nut ) to hold the heat sink firmly against the power MOSFET's.

Lastly, I was able to remove and re-insert the sword without removing the glove box, but this required me to use a lot of foul language as I had a heck of a time with re-insertion. Removal was fairly simple but it did require more wiggling and force than I thought would be necessary. What a stupid place to mount a bunch of power FET's carrying high currents.

Total cost was about $5 Cdn up here in W. Canada and the job took me about 5 hrs. start to finish. Hope this helps anyone tacking this in future.

JJB






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