Another Alternator Wiring Post

[farside847]

Sorry to start another alternator wiring thread, but i could not find an answer searching...

I believe I have a mystery non-stock alternator, that only has two wires attached (red and black). it works great and has been there for years, but i would love to have my battery gauge work again and I believe it is not working because the other wires are not hooked up.

The alternator is a "Delco Remy" with a few numbers on it that are pretty warn. i will attach some pics of it. It looks to be a 55amp. But I really dont know the model. Maybe some of the experts online can identify on sight?

Luckily, the original wiring is still intact, and just taped off. The alternator has a R and F terminal unused. I was thinking of connecting the blue wire to the F connector, and the yellowish wire to the R connector. Before i hooked up my Blue and yellow(ish) wire i wanted to check to see if doing so might fry something. I dont want to damage the alternator, wiring or regulator. Is this the right thing to do?

i am wondering why the alternator was originally hooked up this way. i wonder if the regulator might be bad?

thanks for any help!

[haycatcher]

Just try searching external regulator to internal regulator alternator swap. Also check for inline fuse in engine bay along driver side fender for gauge.

[VetteVet]

That would appear to be a 10 SI one -wire alternator since there are no wires going to the internal regulator terminals in the top of the alternator.

The large red wire is the power output wire from the alternator and it must go to the original junction of the battery, alternator, regulator, and cab feed wire.

This is the original wiring for the 67/72 trucks. The one-wire alternator doesn't need the harness from the regulator so it can be unplugged or left plugged in, either way it has no purpose and will not affect anything except the points inside it will close and stay closed as long as the key switch is on. Therefore it should be unplugged.






Notice the two small black wires in the diagram, these are the battery gauge wires and they have a small 4 amp fuse in each wire to protect the gauge. The wires start at the battery junction on the passenger fender and at the main junction I described above.

They run through the firewall to the instrument cluster plug to pins 1 and 12, and then to each side of the battery gauge. They are both positive so no grounding except for the gauge itself, is needed.




The fuses are easy to spot in the harness and are located in the wiring that runs over the radiator and in the harness below the left headlight, at least that's where they usually are.



This should give you some information to help solve the battery gauge inop
problem and hopefully it explains the alternator as well.

[davepl]

I dunno how this ever worked, as I thought alternators still needed at least the main power line fed back into the excitation/field wire as a voltage reference (stop charging at 14.7V for example). Maybe the stock ones work without it?

I've never tried unplugging the connector before.

[VetteVet]

The one-wire alternators have a special regulator inside which senses the system voltage from the large output wire that is connected to the battery and truck circuits. It is not as good at voltage sensing downstream from the alternator as the three wires which are wired correctly but it usually works ok to keep the battery charged.

If you unplug the three wire alternator it may continue to charge because the fields have some residual magnetism until the engine is shut down and it leaks off.

When the boys loop the small red wire from the no. 2 terminal over to the red wire it does the same thing only externally. If they use this method for the conversion from external to internal regulation. Again voltage sensing is not as accurate as when the no. 3 wire is connected to a junction located downstream away from the alternator.

There are also alternators with magnetized rotors that do not require excitation but their output is still controlled inside the alternator. They run about $300 bucks.

[farside847]

Originally Posted by VetteVet

That would appear to be a 10 SI one -wire alternator since there are no wires going to the internal regulator terminals in the top of the alternator.

The one-wire alternator doesn't need the harness from the regulator so it can be unplugged or left plugged in, either way it has no purpose and will not affect anything except the points inside it will close and stay closed as long as the key switch is on. Therefore it should be unplugged.

Very interesting, so the battery gauge should work with the blue and white wires unplugged from the alternator? I will get on checking those two fuses ASAP.

thanks for the info!