engine harness wiring/1wire alt

[rjs53]

I've looked at lots of old posts about this and have found a lot of info. But in all the posts and pics, nobody says if the brown wire originally hooked to the voltage regulator is hot when the key is on. In pictures and post everyone hookers it to the #1 post on the new alternator, but if its hot when keyed and I have a the +lug wired to the #2 post this seems like an accident waiting to happen. Can someone shed some light on this for me? Thanks.

[LockDoc]

Originally Posted by rjs53

I've looked at lots of old posts about this and have found a lot of info. But in all the posts and pics, nobody says if the brown wire originally hooked to the voltage regulator is hot when the key is on. In pictures and post everyone hookers it to the #1 post on the new alternator, but if its hot when keyed and I have a the +lug wired to the #2 post this seems like an accident waiting to happen. Can someone shed some light on this for me? Thanks.

The brown wire is the exciter wire that tells the internal regulator to start charging (turns it on). That is all it does. Just hook it up like all of the instructions say. All of those people can't be wrong....

LockDoc

[dmjlambert]

More info: the brown wire gets positive voltage when the key is on, but the voltage goes through a brown and white resistor wire and on some trucks also through an indicator light bulb that is between the ignition switch and the firewall connector. So it's not full power 12V as if straight from the battery positive terminal. There is normally some resistance involved.

[rjs53]

I’ll check it for voltage. As of right now I tried it and it didn’t make a difference other than my volt gauge went way down

[dmjlambert]

If you have an alternator that has been modified to be a 1-wire alternator, then you won't be using that wire anyway and it won't make a difference if it is hooked up or not. In your post you don't mention what exactly you have going on, but in the title you do mention 1wire alt, not sure why. These trucks don't come with a 1-wire alternator. They also don't have a volt gauge on the instrument cluster, so perhaps you are talking about a multimeter hooked up somewhere. Are you having any problems with the truck, or just wondering how things work?

[rjs53]

I swirltched to anyone wire alt. The po had hanged to an HEI and had done something so that after charging the battery it would start but die in minutes and kill the battery. I have been trying to sort everything out and have all the gauges working. Not sure if the temp is working because the brown wire was hooked up to the temp sender. From all the schematics I’ve found the brown wire did not go there. My charge gauge is working but not sure if it’s correct or not and the wire has me stumped.

[dmjlambert]

Yes, sounds like you have stuff changed around from the factory setup. It may have never worked right since the PO made the changes. If it were mine I would change the alternator out to a regular internal regulated one, either 12SI or CS series and fix the wiring to be correct including 3 wire connections. And also get the temp sensor wired like factory.

First you can probably just start by having a parts store like Autozone give the battery a good charge and test. A fully charged battery should not get killed in minutes on a running truck.

If you continue to have troubles or just have questions, post your questions here and tell us everything you can about your truck, such as what engine and options you have and accessories you have that are not part of the stock setup (such as electric radiator fans and other high-current-draw items and how they are connected), and how exactly is the HEI power wire connected. If you don't have electric radiator fans or other high-current-draw items you should be able to drive the truck for days and hundreds of miles with a good battery and no alternator at all hooked up.

[rjs53]

I changed to an internally regulated alt. Read my previous post and saw it said anyone not TO A ONE. Dang spell check. So I pulled the wiring bulkhead off the fire wall and rewired it so the purple goes to start on solenoid, red wire goes to hei and the green and brown not sure. Maybe green goes to temp? I deleted the junction peg on passenger side next to battery, ran everything off positive of solenoid except fuseable link. I ran it to hot on alternator and a wire from the battery. Had everything wired like factory but wanted to clean it up a bit. Battery charges now truck runs and idles fine, but a couple loose wires, and I hate to cut them off when or if they are still useful. Truck has a 350/th350 came like this from the factory. Not sure if this is original motor, kinda doubt it.

[Grumpy old man]

This should help .


Post 13


http://67-72chevytrucks.com/vboard/s...d.php?t=692750

[rjs53]

Yes I've looked at the post many times, I have the Si 12 but couldn't figure out why the brown wire had power or if it should. Apparently it should have keyed power but not a full 12 volts. Thanks for the help.