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Alternator stopped working a while back and I replaced it, but the replacement gave the same results (12.4). I've been back and forth testing and replacing things and couldn't figure out what was wrong. I finally found that the green wire that I believe goes to the instrument cluster wasn't getting or giving any reading. So I spliced it into the yellow wire and the alternator kicked in and has been reading 14.2 since.
So my question is, will this cause any damage? Will it kill my battery? I'm not sure if the green wire had a bad connector or a break in it somewhere, or if it's a problem regarding the charge indicator. If it only goes to the indicator, I'm not sure why it would be required for the alternator to start but that's the only thing that got it working. I am looking for a replacement for the wiring harness, but I'd like to be sure that it's not something else causing the issue first.
Not too uncommon for the trigger wire from the dash panel to fail. The work around is to give it a hot that is only on with the ignition. If the trigger wire is always hot, it will indeed drain your battery. I found fuse E (15amp) in the under hood box to meet the requirements. Mine is a 96, so your box may be different, but likely that will work. Easy enough to find out, if it is hot with ign on, & off when off or on accessory, you are golden. I used a fuse tap that plugs into the holder and has a wire running out on its own separate fuse. That approach does require a little trimming of the fusebox lid, if you want it to still close. I ran my wire in small split loom & followed the power brake vacuum hose. Nothing really looks out of place, and it works well, 14.7 with the ac & fan on high.
That was exactly the info I was looking for! I will do just what you did if fuse E is the same (mine says it goes to the Heated Oxygen Sensor). If not I will try fuse 6 (AC Cutch).
Does your indicator still light up initially when you first turn the key to ON? Then goes out after the engine is started? Or does it not illuminate at all?
Yes, it could be the wire itself, but if the bulb is burned out and your in-line resistor has somehow failed too (or perhaps the circuit board?) then you won't get any power on the Green w/red wire to turn on the regulator/alternator.
The resistor is there so that in case the bulb ever burns out, there is still a pathway for some voltage to be routed around the broken bulb circuit and still turn on the alternator even if the light is out.
It sounds like you're on to the fix either way, but just figured I'd ask that question to see what, if any, indication yours is giving other than the alternator not charging.
Ford 3G alternators don't care about too much. I retrofitted one to my RX-7 years ago and it was a breeze. Here's the diagram I made for the retrofit:
On the back of the alternator, there are 3 terminals in the main connector
A: Voltage sense (goes to battery positive terminal)
S: Stator (loops back to single quick disconnect terminal)
I: Ignition (ignition switched 12v source, triggers field to make it output power)
Your battery warning light may work differently than my RX-7's one does, but mine triggers like normal. Besides, the RX-7 has a proper voltmeter from the factory, so the warning light gets ignored anyway
