When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Im replacing my alternator on a Chevy 350 for another vehicle that I have and the alternator has a jumper to the side terminals (white wire) that doesnt seem to make sense. The new alternator I bought can be a one wire or a three wire so Im not sure I need this jumper. The vehicle has a battery gauge but not other warning lights.
Looks like someone did a 1-wire mod already. If you have the wiring to support it, convert it back to 3-wire mode. Otherwise, connect the new alt in 1-wire mode and don't use the two-pin connector.
Are both the sense and excite wires on the alternator spliced to that white wire, and to the Alternator output? Are they hot all the time (since the alternator output is presumably connected to the battery directly, through an intact fuse). Do you have a photo with more pixels?
So I just connected it without the jumped and it runs fine. Im not sure what the jumped wire did anyway.
I'm glad it worked out, and surprised no one else commented.
The jumper was incorrect for a proper 3-wire installation. Since you can't go that route, 1 wire was your only choice. Basically, that jumper is already inside the alternator.
So go drive and enjoy your car (truck?)! But keep an eye on the charging voltage when you drive.
The one negative about the 1 wire alternators is that they tend to need a decent engine "rev" to "wake up". Once they "wake up" they will charge at lower engine speeds, but sometimes without the exciter wire feeding them 12V - they won't charge until you get the RPM's up a bit.
I'd say try it without the exciter wire hooked up (but with a voltage gauge hooked up) - you'll certainly see when the alternator starts charging...
I dont ride it very often so Im sure it will be fine.
That will make it more of an issue if anything (battery will be in a lower state of charge).. but if you havent had an issue yet and your volts are good its likely working fine.
Not a fan of one wire stuff as they generally do not charge at idle.......
The jumped wire is an old trick to excite the regulator......this wire used to come from the inside of the car but folks figured out later on that power is power and jumpes form the output post as it is direct to the battery.
If you brought it to me...it would have the "three wire" setup installed.......and it can be done much cleaner than a wire with a freakin wire nut.....
Jebby
Last edited by Jebbysan; Feb 20, 2023 at 09:19 AM.
Terminal #1 is the "light" wire and it goes to a switched ignition source, it can be direct or through a light bulb or through a resistor. It will get the alternator to excite and start charging at an idle. Without it, you will likely have to rev the engine to get the alternator to start working. The wire can only be switched Only the 10SI and 12SI can be connected directly. Newer alternator need a light or a resistor.
Terminal #2 is the voltage sensing wire. It must be connected unless the alternator has a 1-wire regulator and then it is connected internally. This terminal is on the outside so you can connect it to the point where you want the voltage regulated. For example, connect it to the fuse block and the voltage at the fuse block will the regulated to 14.2V and the output terminal of the alternator will be a higher voltage. this can be used to compensate for voltage drop in the charging wire.
Do I need this extra alternator wire?
