71 Charger, Keep burning up blue alternator wire

[FJ571440B]

 As the title says. Was a new Evans Wiring harness I've had for years just now using. It starts with the key and runs. But by just leaving the key on in the run position for a few seconds the blue field wire at the alternator and up in the dash to the factory crimp got hot and was done. It burned it all the way up into the dash to the factory splice,(from (23) blu/ wht wire in the fuseblock)I rewired inside the dash real nice, cleaned connections, got rid of some nasty soldier blobs, crimped and shrink wrapped all new connections and then as soon as it was back together and turned the key, bam! Cooked it again where it runs along the manifold this time only. I just built nearly this entire car myself including engine, trans, paint and brakes but cannot figure this out for the life of me. I have Nacho's bypass set up but it happened before and with it installed, (10&8G w/14G link, no red wire, removed from cab side of bulkhead). JUST this wire.What gives!??? Thanks for any help! (hint hint Nacho!)

[Nacho-RT74]

Have you checked the brush you are connecting is correctly isolated from alternator chassis? It could be grounded what makes to short out.

On dual field/elect reg setup, both brushes must be correctly isolated. Some ppl become these alternator on single field alternator grounding one of the brushes with a jumper wire or replacing the isolation washer with a metalic one leaving the prong there so connecting the blue field wire there which is positive will short out. Sometimes the isolation mounting get cracked too. This last it happened to me once getting same result than you got.

[Pete in NH]

Hi,

A small inexpensive multi-function test meter would be helpful here and could tell you a lot about what could be going on. If you disconnected both field wires at the alternator and used the meter to measure the resistance between the field terminals you should see 4 or 5 ohms, that is the field winding resistance. Then if you place one meter lead on the alternator case and the other meter lead to each field terminal one at a time you should see an open circuit, no connection at all. This would tell you if there is an issue with the alternator. Next disconnect the positive battery terminal on the car and measure between the blue wire and the negative battery terminal with the ignition key on and off both should again be an open circuit, if not there is a problem that needs to be tracked down.

[FJ571440B]

I'm going to have to bust out the multi meter and test lights etc, this is a brand new alternator also, but I will try and post up my findings later tonight, thanks guys

[FJ571440B]

That was it Nacho, thanks man! Also success with your 8G, 10G and 14G f.link wire set up

[Nacho-RT74]

Grounded brush? Why? Replaced isolator washer for a metalic one or broken brush isolation?

It was also casuality you conected the blue wire there! If it was the green wire instead wouldn't burn anything but just full fielded the alt getting max output from it.

Hi,

A small inexpensive multi-function test meter would be helpful here and could tell you a lot about what could be going on. If you disconnected both field wires at the alternator and used the meter to measure the resistance between the field terminals you should see 4 or 5 ohms, that is the field winding resistance. Then if you place one meter lead on the alternator case and the other meter lead to each field terminal one at a time you should see an open circuit, no connection at all. This would tell you if there is an issue with the alternator. Next disconnect the positive battery terminal on the car and measure between the blue wire and the negative battery terminal with the ignition key on and off both should again be an open circuit, if not there is a problem that needs to be tracked down.

[FJ571440B]

 I get off work around 10 AM today and when I go home I will bust out the multi meter and test light.  I just re-wired everything last night and check to make sure I have the insulated washers where they need to be. Originally, I changed one of the brushes out because the blade that was on there wouldn't stay tight on the connector and it made enough resistance to burn the wire a little bit so,  I pulled one off one of my older alternators and put it on and that is when I put the insulated washer incorrectly on the wrong side.  After I did that is when I started burning wires up through the harness. I finished rewiring it last night, turn d the key on left and it on for about a minute and the wires didn't even get warm so that had to be it. You guys helped my buddy Kernel,(Brian/ Bmotoxstar) that Ive known since we were kids with his harness. He was on the phone with me helping out as I was doing it. He was tickled pink like a schoolgirl when he fixed his wiring thanks to you guys, he really appreciated it and so do I! 👍🏻

[FJ571440B]

Alternator isnt charging. Dies immediately pulling battery cable off. Takin it up to get tested and exchange for another and see in the morning.  All else seems good, starts/runs good, except for the need for a cluster regulator as I have no dash lights. Temp, oil and alt gauges work good though. Gas tank goin back in tonight so Ill assume the fuel gauge works properly grounded. Had to test sending unit, rinse tank, all good.

[BMOTOXSTAR]

Ah...since the gauges work and the lights come on could be the headlight dimmer switch? Try the dimmer. Since the gauges work the regulator should be good? I think.... 

Does the shifter indicator light come on when you turn the headlight switch on?