Sorting out old wiring (1 Viewer)

[workingdog]

I'm trying to do some archaeology on my rig post to engine swaps.

When the smoke clear, under the hood, near the 200 amp alternator (which is not directly connected to the battery with a large cable) they attached the white/blue stripe wire to a new fusible link like it supplies 12v to the cab.

But, looking at the wiring diagram, it looks like that blue white was originally coming from the ammeter to the alternator. I've got new gauges now, no ammeter.

The wiring diagram shows a black/white stripe wire going from the battery through the fusible link to a white wire to the ammeter. The fusible link is long gone and I can't find that white wire.

One of my problems is that my rig is a 66 and I'm always using slightly later model wiring diagrams.

My question is - on a 66, where was the fusible link and in which wiring bundle did the white wire travel - in the same bundle as the white/blue stripe? And is there any need to connect the white with blue stripe up to anything in the cab? Or just terminate it safely. I've just connected the two ends together where the ammeter used to be.

Thanks, Peter

 

[Solace in Solitude]

@Coolerman wrote this in a post I recently read... I have no idea which thread... I copied it for “just in case” reading.

Maybe it will help you... I’m sure Mark will chime in... probably not on the weekend though.

“Fusible links did not appear until the 1972 model year. I do make a kit to allow you to easily add one to your 1966 FJ40.

The below assumes your amp meter is connected and working. If it is not the alternator will NOT charge the battery as the amp meter is in serials with the battery and alternator.


If you have a DC volt meter check the following:

With the truck running you should have +12V on the White/Red wire at the regulator. (That wire should be attached to the regulator Ig terminal, the White Green goes to the F terminal, and the White/Black to the E terminal for ground)


The White/Red wire is the B+ voltage the regulator uses to know how much charging needs to be done. This wire goes back to the fuse panel so check the fuse that has the White/Red wire on it. If you do not have that +12V it will not charge.


If you do have the +12V on the White/Red wire, and all the wires are connected in the correct place then verify that the regulator is grounded well. It grounds through the mounting bolts for the regulator. If you did not clean out the threads for the bolt holes that mount the regulator, it may not be grounded well. The White/Black wire that attached to the E terminal (Earth or Ground) is the MAIN ground for the entire vehicle! So if the regulator body in not grounded well, neither is the rest of the truck...


Still no charge after verifying the ground? Set your meter to low OHMS and meter out the White/Green from the regulator to the alternator plug. First unplug the alternator plug to isolate the White/Green and White/Black wires. Put the red lead into the connector for the Green/White wire and the black lead on the Regulator White/Green wire (F terminal). You should have <2 ohms or good continuity between those points. Do the same for the White/Black wire. If these are good then leave the connector out of the alternator for the next test.


Testing the alternator:

To check the alternator itself you will need to make a jumper wire or clip lead long enough to reach from the alternator to the battery + terminal. Attach the end to the battery + terminal then put your meter in DC volts mode and put the red lead on the battery + and the black lead on battery -. Write down the reading. Should be about 12.7 to 13.2 volts if the battery is fully charged. Leave the meter connected to the battery and start the truck.

Use the clip lead to CAREFULLY and momentarily, apply +12V to the alternator terminal the Green/White wire was connected to. This is the F terminal. Doing this will cause the alternator to go full field meaning it will put out maximum charge current. The volt meter should now read 14.0 to 15 volts if the alternator is working. Do not leave this connected for more than the time it takes to look at the meter!


If it passes this test then you have a bad regulator or a wiring issue. If it does not pass this test you have a bad alternator...”

 

[workingdog]

Thanks for that, but I got none of those parts. I thought that about the fusible link, nice to have it confirmed.

 

[Dizzy]

The fusible link on later models prevents everything but the starter from getting too much juice and frying.

It sounds like your battery supplies the ignition switch without the alternator hooked up, right? And, basically, the alternator charges the battery on its way to the ignition switch.

That is my understanding of it.

Obviously, with an ammeter, you have a line that runs to the combination meter, so there is where the mystery lies. Can you just T into the battery line with your alternator immediately after you install a fusible link on the positive battery terminal, without even going into the cab? Is it cleaner to run the battery to the starter, then the starter lug terminal, to the fusible link, then to the ignition switch? I definitely would not just safely terminate a line, I'd go to its source and disconnect it if it is energized from the battery.

 

[workingdog]

Dizzy - Thanks for the reply. Yes, that's right, alt goes directly to battery. I've essentially done what you suggested and now I'm trying to figure out what to do with the white wire and the white/blue wire that are near the battery.

I ran a new lead from the new fusible link to the new Painless fuse block that supplies everything in the cab. So, in theory, the white wire isn't needed any more. (My 66 had the ancient tube fuses mounted to the firewall).

The white wire was terminated in the harness near the battery during one of the engine swaps - and I agree I don't like that. But, what I can't get is that the white/blue has power. If the white isn't hooked up, then the white/blue should be dead. All I can figure is that one of the connections in the cab to the old harness must be back powering the white/blue.

I guess I'll have to disconnect the battery and get out the continuity tester. This is what I get for trying to splice together the painless fuse block and the original wiring harness.

 

[Solace in Solitude]

This is a ‘70 schematic...
http://www.globalsoftware-inc.com/coolerman/fj40/schematics/FJ40/1970FJ40/1970 FJ40.jpg
It shows W from starter to ammeter.

But, WL runs from the fuse box (5th fuse from top (2nd 20A)) to the alternator... with a T to the ammeter.

Your WL is probably still hot at the fuse box... assuming ‘70 is similar to ‘66.