I'm helping a buddy diagnose a no-charging condition on his 86 245. It's got the typical crumbling wiring harness, with the small red alternator exciter wire in the worst condition. If we want to run a new exciter wire, what guage/type would we need and where would it connect upstream from the alternator?

Thanks.

Light guage, it carries very little current. It goes to the instrument cluster. As suggested just trace it back to the firewall and connect there. I believe it is red.
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David Hunter

It's 18 gauge I am pretty sure, but you could use 16 guage just in case. You should use wire rated for engine temperatures. I have used wires from late model junkyard 700 series. You should be able to pick up the red wire at the firewall connector. It is a grey connector for 8 wires.

Running the wire the same way as the original is a bit of a pain. It runs under the front of the block so you have to take the belly pan off. If you run it this way you should also put a cable protector on it. I would also run a new oil pressure sensor wire while you were at it.

I have also run a wire across from the passenger side without any problems.

Thanks, guys. I'll run a wire to the oil pressure switch while I'm at it. Wires to it are toast.

Inga is an 86 245DL and her four grey harness wires were in really bad shape. The starter solenoid wire was bare for at least five inches when she moved to my house. Still started right up but it was a matter of time there. Then got the dread warning lights coming on and it was time to replace wires. If the oil pressure and exciter wire are bad the starter wire and water temp wire are in at least as bad a shape.

Inexpensive solution is to go to an auto parts house and purchase a trailer harness (Both sides). Cost me less than $6 and the wires are TFE (Teflon). That makes the insulation good to over 800F so not problem using them under the hood.

One more suggestion ,(unless you just want to get greasy) is to run the oil pressure and exciter wire down the firewall and passengers fender to reach the pressure switch and exciter wire. The connector on the oil pressure switch is almost impossible to find without slicing one off a donor harness so you want to try and save the one on your car.

While you are in there around the alternator, check out the blue ground wire that goes from the Alt frame to the engine block also. That wire gets eaten up over time and you need a good solid ground to the frame of the alternator to have a good charging system.

Had the connector installed for going on three years and 50K miles now and still working like a champ.

Regards,

Paul

thank you so much for the trailer harness idea. My 86 245 wires are in need of attention and your idea is perfect.


280,000 miles on an 86 245
200,000 miles on a 93 945

Boy, I sure do like the trailer harness idea. The wires coming out of the bundle to the right side of the gray junction box are crusty, too, so might just run the 4 wires all the way to the back of the cluster to be safe. Thanks.

If you slice the black cover back a few inches, you most likely will find good clean wires up in there. The key is to get the old wires back under a good moisture free cover like heat shrink and good electrical tape. The crap insulation is fine away from heat and oily grime. Sadly under the hood is nothing but heat, oil and grime.

Good Luck,

Paul