Alternator experts

[Tinman]

I'm running a one wire alternator on the V8 rx7 and would like to switch to a three wire. From what I understand the internal voltage regulator is different between the two and this one is advertised as having a "special regulator" for 1 wire operation. But as it was delivered it had a jumper wire from the output terminal to the alternator exciter terminal. This leads me to believe that the regulator is no different than a standard one and the jumper wire is their "special regulator". So can this alternator be wired for three wire operation or do I need to swap it for something else?

[Lustalbert]

The 1 wire units have the regulator built in. 3 wire units have an external regulator. The 2 terminals go to the field coil. The jumper provides +12V to the field coil, and the internal regulator adjusts how much resistance is on the ground of the coil so it can vary the strength of the magnetic field. Just a matter of getting an external regulator and diabling the internal one.

Question: why go to 3 wires? Just 2 more wires to route and potentially break or cenections that can corode/come loose.

[Tinman]

I would like to ditch the one wire because the three wire system does a much better job of sensing voltage requirements. As it stands now the one wire only puts out 11.5v at idle with the lights or fan on and doesn't hit 14v till around 2500rpm. That and there is a drain on the battery when the car is parked, the alternator is the only thing I can think of that is causing the drain.

[Guest Removed]

If it has a jumper wire, Its not a one wire at all!!! my gm one wire alt, charges 13.8 to 14.2 no matter what, and that jumper wire is most likely causing the drain, do to the fact it is keeping the alt on all the time, but even with the jumper wire in place , on some other cars ive done, normally doesnt cause a draw unless something in the alt went bad!

 

Standard Gm 3 wires alt's need the jumper wire to work properly..And if it has more then 1 wire, it is not a 1 wire!

[Tinman]

Alternator in question #77-500. Which is the same alternator that came on most 90s Hondas and probably many other cars. I could just buy stock Honda alt. but would like to see if I can make this one work in three wire mode and save a couple hundred.

[nurkvinny]

If it has a jumper wire, Its not a one wire at all!!!

 

My "1-wire" GM alt has a jumper wire. The 1 wire only refers to it taking 1 external wire to hook it up.

 

Tinman, I have a 110amp 1 wire I had built a few years back if you would want to try it.

[Tinman]

My "1-wire" GM alt has a jumper wire. The 1 wire only refers to it taking 1 external wire to hook it up.

 

Tinman, I have a 110amp 1 wire I had built a few years back if you would want to try it.

 

I appreciate the offer but I want to stick with current alt. mount and drive system. This one only puts out 60 or 70amps but that is plenty for my car, I just need it to put out the amps when the electrical system is calling for it.

[gillbot]

Some 1 wires have a "weaker" field excitation requirement. This allows them to get more power from the "hot" terminal at lower RPM's. There's a handfull of things to switch if you want to go back to a 3 wire. Some insulating washers and the like will need to be replaced inside the unit.

 

I can't say how the one you have is wired or configured but the USUAL setup requires changing the internal regulator and removing a couple insulators from the inside. Placing a 3 wire regulator without replacing the insulators will fry the 3 wire regulator quickly.

[Tinman]

Well damn, a new regulator is just as much or more than a new alternator. Thanks for the info James.

[Lustalbert]

@ idle, an 70 amp wont keep up with that kind of load. It is only making 20-30 amps at low RPM. Smaller pulley to spin fater, or difrent regulator setup, or larger alternator. Check to see what the ouput is rated at. (60 amp @ x,xxx RPM @ xx*F)

[Guest Removed]

My "1-wire" GM alt has a jumper wire. The 1 wire only refers to it taking 1 external wire to hook it up.

 

Tinman, I have a 110amp 1 wire I had built a few years back if you would want to try it.

 

 

Thats funny, I have at least 3 GM 1 wire alt's sitting here, and all of them only have one wire! The 3 wire GM alt's ,I have 1 jumper wire, to make them work...Even the ford style 1 wire alt i put on chucks car, only has 1 wire..

[Tractor]

Since I recently reconfigured a GM alternator for welding I'd say the alternator that is on the car now even though it is supposed to be a 1 wire is actually just a jumpered 3 wire unit. So its basically just putting 12volts from the battery to the field and to the regulators reference voltage terminal. A 1 wire set up can be done with the jumper on the outside actually going from one terminal to the other at the harness or can be jumpered on the inside of the casing.

Maybe the reason a normal 3 wire alternator seems to charge better has something to do with it detecting the differential between Vref and Vte at lower RPM's were as a 1 wire set up will simply energize the field and output voltage as RPM's increase until it reaches its most effiencent RPM/voltage output.

So after all this I"d say you could simply rewire it for a 3 wire configuration if you feel like it.

 

Evan

[gillbot]

Try rewiring it and see what happens.