I have a 1973 f100 with a 390 and i cant seem to find the correct wiring diagram for my voltage regulator. Does anyone have one?

I may have found out why my truck wasnt charging.

 

this will do it.

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Yeah, that'll do it!
Does your truck's instrument panel have full gauges, including an ammeter? Or are there indicator lamps and few gauges?
The voltage regulator wires differently for these two scenarios. Looks like the 4-wire regulator connector has been changed for a new store-bought one, based on the cleaner wires and incorrect colors.

If you have gauges, there are only three positions utilized. If you have a charge indicator lamp, all four wire positions are used.

Are you still using a standard alternator for your year truck with the external regulator?

Paul

 

Yes i have full gauges in my truck, and i am using a OEM style altenator for my truck. I know the solid green wire goes to my gauge, i have the field wire reconnected now, i have no idea where the two yellow wires and two white wires run to. Thank yiu very much for the reply

 

Unless '73 was different, your regulator is wired incorrectly then. Don't take any of this as gospel until some others chime in to confirm or deny (and I'll check the book later too) but with full gauges the regulator and alternator are wired thusly:

1. "F" - Field wire (Orange) runs from the "F" position on the regulator to the FLD terminal of the alternator.
2. "S" - Green w/red stripe runs from the "S" position of the regulator to the ignition switch directly. Has 12v in RUN only. Not in ACC.
3. "A" - Yellow wire(s) run from the "A" position of the regulator connector to the battery. Has full battery voltage all the time.
The second Yellow wire runs a short distance to a radio noise suppressor choke that looks like a condenser/capacitor (because that's what it is) and reduces radio static.

With just lights, the letters stand for Field, Stator, Armature, Indicator.
With full gauges, the letters have different meanings and I've given them the following designations. F is still field, S is "switched", A is "always" and I is not used.
That's important. Only three wire positions are utilized in trucks with ammeters. All four are used in passenger cars and trucks with indicator lights.

The Green w/red wire is what turns things on and tells them it's ok to charge when the alternator starts spinning. Should have as close to 12v as possible, but a volt or two missing won't kill the deal usually.
The Yellow wire should have as close to full battery voltage as possible. If it's down by less than half a volt, you're probably ok. But if you measure a loss of more than a volt, I would check and replace if necessary.

There may be a White w/black stripe Stator wire from the alternator's STA terminal, but with Fords of your vintage, I'm pretty sure they were only used to power up the carburetor's electric choke. The trucks I know all got them starting in '73, but I'm not sure if that's universal or not.
As I said, I'll check the book as soon as I can to make sure I'm steering you straight. What I said is how it works on Broncos and at least the later seventies trucks I'm more familiar with.

Hope that helps. Good luck.

Paul

 

Thanks again paul. I appricate it. Im going to keep looking for a 73 wiring schematic but still havent found anything. The 74-79 are the same and are designated 74 - 79. 67-72 is designated for 67-72 so that makes me believe my 73 is different. Its driving me nuts

 

The red wire went through a fuseable link to the yellow wire i hooked it too. The other wire im unsure of where it goes. This plugs into the main truck harness

 

So that's the alternator side harness?
In the Hayne's book they're broken down into '73 by itself, '74, '75 and '76 together, '77 by itself and '78/'79 together.
I'll see if I can find anything on the '73 diagram that might help.

Paul

 

Yes sir, this goes to the altenator side to tie in with the wiring to the regulator. The batt wire goes from altenator to this plug then splits to the starter solenoid. Theres also the standard two prong plug and the horn wire as well. This has me all confused. Ive rebuilt these soooooo many times and never seen one like this.

 

Well at least the concept is straightforward. So you can literally re-wire it yourself to get it all up to snuff and just be out a little time and a few feet of wire.

Simple enough, as the Black w/yellow wire connects from the alternator's BAT terminal directly to the starter relay on the battery side.
The Orange wire runs directly from the F terminal on the regulator to the FLD post on the alternator.
A Black wire runs from one ground bolt to the regulator ground bolt.
And that's it, for charging duties. Period...

For the electric choke on a stock carburetor, you need the STA post on the back of the alternator to run directly to the Ford choke coil. If you have an aftermarket carburetor though, this wire goes unused.

For the Yellow, it's either the horn relay main power or the ammeter feed.
If it's just the horn relay main power it can be run to the battery side of the starter relay directly. The original would have a fusible link on it, and I think you mentioned that. A Yellow wire from the factory without a fusible link is probably for the ammeter.
If your plug that we see in the pic has three wires out the bottom, but only has connections for two wires on the top, then the Yellow wire in your hand is simply spliced into the Black w/yellow wire (inside the molded rubber connector) to get it's power for the horn relay or signal for the ammeter.
Assuming your truck even has a horn relay that is. Not all trucks did of this vintage.

While it's nice to have a working ammeter, it has no bearing on whether the alternator charges or not. Only whether or not you can read about it on the gauge. So just to get things charging, you don't need the Yellow wire just yet.

Maybe instead of trying to figure out all the odd colors and directions then, just "roll 'yer own" so to speak.
I don't have that connector on mine. The Black wire runs straight from the back of the alternator to the starter relay. The horn wire gets it's power straight from the battery side of the starter relay as well.

Paul

 

THANKS PAUL! Im going to make this harness work for now then ill build my own shortly. Youve helped out a ton man!

 

Cool! Now come on 14 volts!
If you see 14.5v or so on a meter when the engine is running, you're in the money. If you see less than 13v, it's not charging right. If you see over 15.5v it's charging too much and likely an issue with the regulator.

I just noticed in the pic your special best-bud electrical wiring guru helper 4-legger type under the table there!
You're set then!

And just for giggles, can you post up a pic of the backside of that alternator? Just curious the layout, labels and colors of the insulators to see if they've changed.

Thanks

Paul

 

Well my battery was dead, like really dead. Im taking it tomorrow to get it warrantied out then trying this again. To get the truck to start i had to jump it off for over 30 minutes, i pulled the battery terminal and it kept running. Tested voltage and it was dropping .02 volts per every about 2 seconds. If i revved it it would hold constant voltage. Im hoping the battery being so dead is causing the alt not to charge correctly.

 

I got it fixed paul! Under full load shes pushing 13.57 volts! The yellow wire that was in my hand in the picture is the signal wire! Found out the hard way lol.

 

Oh btw, thats Scarlet! Shes definately a one of a kind pupper, shes an Olde English Bulldog. Last September we had a huge flood here south of Houston and she was a rescue. I rescued her, and her family. They called me acouple weeks later asking me to take her cause they couldnt care for her anymore, shes my partner in crime now!