Hot Rod Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
4 Posts
Thanks for that info sedan delivery - I think it will help me out in my effort to figure out what's goin on with the wiring in my truck. In short, I bought a 1985 S10 pickup that originally had the 2.5 4 cyl. It was replaced with a 1980 (carbureted) 267 C.I. V8 engine. Most of the original wiring harness, in the engine bay, is not used and tied up to the firewall. Just the essentials (Batt., starter, alt., oil, temp., etc.) are in use. The problem is the charging system - does not charge (when I remove the battery cable, it dies). The alternator tests (Autozone) good, so one or more of the alternator wires is not connected to the proper place. I should mention that aftermarket gauges are installed, therefore bypassing the idiot light. It is my intention to get rid of the aftermarket voltage gauge and use the original idiot light. I am totally ignorant on wiring connections, so the diagrams I downloaded and printed should help me to understand more about it and get it charging properly. I am not concerned about the remaining wiring harness as I don't intend to use anything else in the interior, other than heater, wipers, and stereo.
 

·
Registered
Joined
·
3,111 Posts
On the alt there are basically 3 connections

The Alt pig tail has terminals 1 and 2

Terminal #1 from the alt goes to the one side of the idiot light on the dash. The other side of the idiot light goes to a switched 12v source (hot when the key is in the run position) This is the exciter wire and tells the alt to start producing juice. The idiot light does not get a ground wire, it gets a ground from the internal regulator in the alt when the alt isn't spinning. That's why it lights when the key is turned to run but the engine isn't running, and it goes out when the engine starts. You do not have to have an idiot light or a resistor, you can have just a switched 12V running to the #1 terminal and it’ll work just fine.

Terminal #2 from the alt goes to the hot side of the wiring system, normally it’s spliced into the hot feed leading to the fuse box. This is the sense wire, it tells the alt to produce more or less juice depending on the demands of your electrical system.

The large lug on the back of the alt is the output wire or charge wire and is normally tied directly to the pos post on the battery via a large gage battery cable.

You can use both the gauge and an idiot light. You can tie the gauge into any switched 12v source and it'll work just fine. My guess is your exciter wire isn't connected to a 12 volt source (other side of the idiot light)
 
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top