[HO455]

Originally Posted by jumpsoffrock

Can I add another charging wire in addition to the factory 12ga wire?

I am adding a large electric condenser fan and also prepping for any possible future electric mods. I am going to carefully tear apart the junction area near the drivers headlight and essentially insert a new 10ga charging wire from the alternator.

The trucks original harness to the alternator has one 12ga red and the white and blue wires, and I have always been hesitant to simply chop off legs of the original harness, even if not in use.

Then I thought, can I simply add the 10ga wire, splice it in as near to the 12ga red, and keep the factory 12ga red charging wire, as long as the exciter wire goes very near to where they are?

I was intending on simply splicing a new exciter wire to wherever the 10ga wire enters the harness.

Thank you.

As expressed earlier the stock 37 amp alternator isn't likely to be up to the load you are anticipating. The stock charging system doesn't like to run at full load for extended periods of time. When it was designed stop and go traffic wasn't considered. As a result when you add extra load one of 2 things usually happen.

Your battery slowly goes dead as the alternator output at idle is lower than the full rating of the alternator. Stop and go traffic means your idling more than you are running above 1200 rpm. Your battery is discharging as the load has exceeded what the alternator can supply.
The second thing that is likely to happen is after repeatedly having to charge for extended periods the regulator or the alternator will fail. GM designed the system to charge at full load to recharge the battery after a deep discharge then maintain the battery charge. The components will overheat if they have to run at full load continuously.

Simply adding a wire between the alternator output and the harness splice isn't likely gain you any additional charging from the stock system unless there is an existing problem with the factory wiring. The addition of the second wire will change the balance in the charging circuit and your amp guage will no longer work correctly. (Assuming you have an amp guage and it still works.)

If you do increase the amps your alternator can supply adding a wire like you said would keep from overloading the factory charge wire but, it is only part of the circuit. The rest of the circuit between the splice and the positive post of the battery will still be original. So let's say you upped the alternator to 60 amp output and your new wire means you can safely supply that 60 amps to the harness. Then you leave your lights on and have to jump start the truck. With the battery so low the alternator will be supplying full output and you will have the stock wiring between the splice and the battery trying to carry 60 amps. If your fuseable link is still good it will eventually pop as designed. If somewhere in the past someone removed it you will end up melting the harness and possibly shorting the alternator to ground. That just ruins your whole day.

If you want to keep your truck as stock as possible you could change your harness, alternator and regulator to the factory's 61 amp system. There is very little documentation on that system even though it isn't that uncommon. I have yet to locate a correct wiring diagram for it. As far as I have been able to tell the factory (At least on 67-68's) upgraded the regular harness with additional wires and junction blocks all sized correctly to carry the load and have the amp guage work correctly

I upgraded my alternator and the original harness on my Burban, and you may find some information that would help in the link below. Scroll to post 466.

https://67-72chevytrucks.com/vboard/...698377&page=19