Multiple charging wires from alternator
 

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.

Re: Multiple charging wires from alternator
 

Are you are using the stock alternator? It will not have enough output to run most radiator fans. If you have updated the alternator the 10g wire may be too small. Basically I need more information to be of and assistance. Alternator size and fan draw for starters.

Re: Multiple charging wires from alternator
 

Be careful with upgrading wires, automotive wire is different from household wire, is different from marine grade wire.

Bigger is not better, if you up size a wire you can feed a circuit too many amps causing things to fry and cook. Especially the heater circuit. Fans will continue to take more amps if fed more juice. This is in the dash circuit and feeds through the ignition switch which in turn will cook more components.

GM did some pretty trick stuff to regulate power and conserve the use of copper in the electrical wiring so you have to take that into consideration. Look up some threads in the electrical forums, you will see folks have had some interesting experiences trying to do upgrades, myself included.

Re: Multiple charging wires from alternator
 

i would think going with a larger wire to the main splice would be fine since thats where the power for the whole vehicle is drawn from i went with an 8 gauge wire . http://www.madelectrical.com/electrical-tech.shtml read this if you want to make electrical upgrades full of great info

Re: Multiple charging wires from alternator
 

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

Re: Multiple charging wires from alternator
 

This is not true. The wire gauge isn't used for current limiting unless it's used as a fuse. :lol:

Re: Multiple charging wires from alternator
 

Yes, you can add another wire in parallel without any ill effects.

Re: Multiple charging wires from alternator
 

If you are running a stock alternator with a regulator I would ditch it for an internally regulated CS or SI style alternator. If you don't want to change the alternator pulley on a CS style alt you can opt for the a 61amp 10SI or 12SI if you need more amps. We can't tell you if the 61 amp alternator is sufficient with out knowing the fans amp draw. I would leave the factory 12ga. alternator wire in place and then run an "alternator bypass" wire from the alternator to the large battery wire post on the starter. This would eliminate the need to mess with the factory splice or upgrade the fusible link.

I'm assuming you plan to run this fan with it's own relay.

Re: Multiple charging wires from alternator
 

X2. I did this just a couple of weeks ago after I installed a 100amp alternator. I ran the parallel wire to the stock distribution block using a fusible link to protect the circuits. I'm now getting the full benefit of the high output alternator.

Re: Multiple charging wires from alternator
 

I added a 10g wire from the alternator to the battery in parallel to the factory wire. This is on my Chevelle when I put a 100 amp power master with external regulator on with the duel electric fans . Been 7 years not one problem with it . I most likely went too large a wire but better safe than sorry

Re: Multiple charging wires from alternator
 

Sorry for the lack of update. I now use a 63 amp unit from a '78 chevy truck.
Yes Kev, the fan will be ran by the popular Volvo fan relay, connected directly to my new junction block.

I am going to add a 10 gauge wire from the alt to a new junction block near the passenger headlight and connect that junction to the factory harness(using the old plug connector from the original volt regulator). I will also add an additional 10 gauge wire from that junction block to the factory junction on the passenger side.

Although I do not know if I should add another fusible link. I have a funny feeling all of my meddling is kinda causing a "go-around" of the original fusible link and therefore it isn't even necessary.

I do not think I will ever tax my charging system enough to cause it to burn up my original harness.

Re: Multiple charging wires from alternator
 

You have a plan. The amp gauge will no longer work but they rarely do anyway on our old trucks. Cheers.

Re: Multiple charging wires from alternator
 

It sounds ds like the new wire feeding the relay is a stand alone circuit that is independent of the truck circuit other than being fed from the alternator. If this is the case the the addition feeds its on circuits or fuse panel then the original wiring is still intact and the amp gauge should read the charge level going to the truck wiring provided it doesn't go outside the gauges calibration area. I believe the key is that ots two circuits with the amp gauge on one and not a parallel circuit that can feed around the gauge.

Edit: I just reread his intended routing and Accelo is correct. If the OP leaves out the jumper to the original voltage regulator plug what I typed should be what happens.

Re: Multiple charging wires from alternator
 

If the gauge was working before it will still work.

Re: Multiple charging wires from alternator
 

You may never have a problem with your fuseable link. But if you did it isn't likely to be convenient.
But with your increased amperage from the alternator you could end up in a situation where the battery is charging at a higher rate than the fuseable link can carry.
Or if the engine wasn't running and your fans, headlights, wipers, heater, radio and such were on and you tried to start the engine you could draw more current from the battery than the fuseable link can carry.
When starting the engine the system voltage will drop and thus amperage will increase at every load. It's that Ohms law thing.
At the minimum I would recommend carrying a spare fuseable link or two so you won't be stranded if the worst happens.

Re: Multiple charging wires from alternator
 

(I'm just writing this for my own record)

The condenser fan I'll be using is a pusher fan from ~1984 Mercedes; I saw one in the junkyard today and the fusebox dictated a 16amp fuse for it. So that gives a good idea of what draw I'll be encountering from that.


I bought two additional gauge panels to toy with as I plan on doing some DIY gauge mods, but if I am as stupid as I think I am and ruin the gauge panel with my shabby mods, I can always go back to my original and just add the typical aftermarket gauge pods and be done with it. I appreciate the aftermarket solutions but I don't budget for that kind of stuff.

I'm gonna try and swap amps for a voltmeter pod from a squarbody, so if my new circuits mess with the function of the factory amp meter(yes it works fine) then so be it. https://www.garagejournal.com/forum/...lies/dunno.gif

http://67-72chevytrucks.com/vboard/s...d.php?t=680817

https://www.youtube.com/watch?v=xNPF1u9K9dQ

Re: Multiple charging wires from alternator
 

Do some looking around on this site. I haven't done this mod myself but I seem to remember several people taking apart a cheap auto parts store volt gauge and installing the factory needle and installing inplace of the amp gauge. Makes it a cheap mod with a new gauge. Reworking a stock cluster can be very painful but this looked pretty simple.

Re: Multiple charging wires from alternator
 

Tbone1964 sells volt gauge conversions in the parts forum. https://67-72chevytrucks.com/vboard/...ght=volt+guage
As mentioned bigger wire never causes a problem except for less flexible and taking more space. BTW #10 wire = 30 amps. Many think that stranded wire is better for DC current. It is the opposite. Better for AC, difference is really marginal. Fine stranded wire is more flexible so it is better suited for automotive applications.

Re: Multiple charging wires from alternator
 

The 2nd easiest voltmeter conversion is to swap a square body voltmeter in to the ampmeter spot in the panel. Do search there are several threads on how it's done.
The 1st easiest is to get the TBONE1964 guage