The Stovebolt Site Forums The Shop Area The Electrical Bay One Wire Alt Conversion

I know that changing to a 12v alternator setup is common but wondering if theres a plug/ pigtail, etc to enable a clean one wire alt setup to get the wires from the firewall mounted regulator to the alt or do those wires just stay at the firewall and the pigtail pickup at the leads that originally attach to the generator? Long question - hope it makes sense. thanks guys

"One wire" is a myth. It requires two, at a minimum, but one of them is only about 3" long.
Jerry

What is the 3" wire connected to, Jerry?

I had a 12v one-wire alternator a few years ago on 12v (conversion) 54 truck with 6-cylinder engine. I do not remember 2 wires being attached (by me) to the alternator (but, my memory on this is very dim. I bought the 1-wire alternator - I did not convert an alternator to 1-wire.

Here is the "wiring" diagram I used - found on the Internet.
Taken from the old web page.

The 10SI alternator that most everybody uses has two blade terminals on the outer perimeter of the housing and one large terminal at the back where the main charging wire attaches. The two small blade terminals are on the onboard regulator, and one of them needs to be connected to the charging output to monitor the voltage. Some (not all) regulators will self-energize from the internal circuitry of the alternator without the external reference lead connected, but it usually requires the engine RPM to be goosed after starting to begin the charging process. To make a 10SI charge at idle speed without the initial speedup, connect a short jumper wire from the main charging terminal to the blade terminal marked "2" on the perimeter of the alternator housing. The #1 terminal grounds an idiot light if you choose to use one.
Jerry

I have a 1 wire, there is a internal regulator that jumps to the terminal to activate it, cost less than 10 bucks (the regulator). I have had it for over 10 years and works great. I do not have a gauge hooked up.

My true 1-wire alternator "became excited" at around 700RPM - which is what the start-up RPM was/is on my 235/261 trucks. Once "exited", the alternator stays/stayed excited.

Hot Rod Lincoln That is interesting I am familiar with the 1 wire alternators from them being used to replace generators on older farm tractors. When the one on my Farmall Cub failed I went back with the Delco with internal regulator because the Cub engine would have to be revved to the 1800 rpm governor limit to excite the alternator. That and the 1 wire is $20 more expensive.

GM used the same wiring system- - - -they just connected the constant 12V reference from another location, possibly the fuse block, IIRC. Some people claim the jumper from the main charging connector to terminal #2 is too close for good voltage regulation, but since electricity travels at approximately the speed of light, I can't see where a few feet compared to 186,000 miles per second makes much of a difference.
Jerry

The way I was taught to wire them was connect main charging (BATT) terminal to battery positive at battery or starter solenoid and terminal 2 to ammeter and ammeter to ignition switch. The first one I used was off of a mid 80's Old's Delta 88 it would peg a 60 amp ammeter at engine start, then drop to less then 10 amps.

1965t5, there is an easy way to do it the way you describe in the initial post. Not sure what year model truck you have, but here is how it works on my '57 3600.

Leave your voltage regulator where it is on the firewall. Use it as a dummy and a terminal block. Disconnect the ARM and FIELD wires at the regulator. You will not be using those terminals. Re-purpose one of the generator wires that ran to the voltage regulator by making it the 'one wire' for your new alternator and connecting it to the BAT terminal on your old voltage regulator. Keep the battery feed and the gauge feed on the BAT terminal (no change). Your firewall mounted voltage regulator will no longer function, but will still be there. The BAT terminal is now simply a junction terminal.

If you opt to use a three wire alternator (less expensive and better voltage reading), the installation is almost as easy. You'll need a diode in the ignition wire, but you can wire one in yourself with a Radio Shack diode or you can buy a plug that includes the diode for about $10 on eBay. Wire as described above, but also connect the remote voltage sensing wire to the BAT terminal of the existing voltage regulator. This will allow the internal voltage regulator on the alternator to operate using a voltage reading from the load at the junction terminal instead of at the alternator. Wire the ignition wire (the one that requires the diode) to the ignition switch side of the ignition resistor on the firewall. Very easy. Don't be afraid of a three wire thinking it is a more difficult installation. The remote sensing wire will give you better performance when lots of accessories are operating.

Matt

Thank you all for the comments - this helps alot