Alernator 3 wire Versus 4 wire
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Alernator 3 wire Versus 4 wire
I have been trying to work out the major alternator related issue I have. I found one problem in that the wires going to the alternator were questionable. However, Before I fix that I need to ask a question. I have an 88 iroc. According to the wiring diagram in hynes the car originally had a 4 wire alternator. Along the way a 3 wire alternator was placed in and the 4th wire was tapped into the 3rd wire just after the alternator. The questionable wiring part was this connecter. Before I fix it however I need to know. Will tapping the wire for the gauges and volts into the wire for fans cause problems? Will fixing my wiring problem handle potential issues there or should I consider finding a 4 wire alternator.
Last edited by graywolf624; Dec 14, 2003 at 12:35 PM.
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Joined: Dec 2003
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From: Newark, DE
Car: '86 Camaro, '02 WRX, '87 K5, '67
Engine: 350 TPI, 2.0turbo, 383 in the works, 289-4BBL, 232, A-head 4-cylinder
Transmission: T56, 5-speed, 700R4, C4, T176, semi-auto 2-speed
Axle/Gears: 3.73, 3.90, 4.88, 3.55, 3.54, 7.00
The funny thing is that you only need three wires to run a 4-wire alternator. Typically one of the terminals is a dedicated voltmeter signal, but GM often didn't even use it, so there are cars out there with 4 wire alternators and functioning voltmeters that only have three wires tapped into the alternator.
You will need the heavy gauge wire from the alternator to the battery (it should be at least an 8 gauge wire, especially with a high amp alternator). Then there are typically a smaller gauage red wire and a brown wire that go to two of the pins for the 3-wire plug in connector. One is for the stator and the other is for the rectifier. Some people bypass the rectifier wire in an attempt to get a "one wire" hookup, but this is a bad idea and can cause voltage spikes.
I just did a serpentine drive swap on my '86, so I went from an old three wire 12SI style alternator to a new style 4-wire unit for an '88-'92 car. I connected the wires as mentioned above and it has functioned flawlessly since the install.
I would try to tap the wire for the gauges into the factory gauge power circuit. The fan control circuit is stypically a fairly large draw item, even though it uses a relay, so you don't want to risk overloading it. The volt gauge can be tapped into the factory wire for this, or run from the unused terminal on the alternator.
You will need the heavy gauge wire from the alternator to the battery (it should be at least an 8 gauge wire, especially with a high amp alternator). Then there are typically a smaller gauage red wire and a brown wire that go to two of the pins for the 3-wire plug in connector. One is for the stator and the other is for the rectifier. Some people bypass the rectifier wire in an attempt to get a "one wire" hookup, but this is a bad idea and can cause voltage spikes.
I just did a serpentine drive swap on my '86, so I went from an old three wire 12SI style alternator to a new style 4-wire unit for an '88-'92 car. I connected the wires as mentioned above and it has functioned flawlessly since the install.
I would try to tap the wire for the gauges into the factory gauge power circuit. The fan control circuit is stypically a fairly large draw item, even though it uses a relay, so you don't want to risk overloading it. The volt gauge can be tapped into the factory wire for this, or run from the unused terminal on the alternator.
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