All right I thought I did all my homework first but I guess not.

The alternator took a puke officially yesterday on my 99SE. I had the alternator and tensioner assembly plus the 2 wire conn. off of a 07 Grand Prix. I've got everything installed and running again but with one small issue.

The 2 wires that come of the back of the 07 alternator I thought were a sense wire and a signal wire, but not sure which does what.

I'm not sure what the original 2 wires were for (first mistake), (second mistake not having a 99 FSM).

As it sits right now: the car starts and runs but the gauge only shows 12.8v. I took a reading at the battery with the car running and got 13.8v. These 2 readings were taken without any of the 2 wires from the conn. connected.

1. What do I do with the 2 existing wires for the 99 alternator?

2. What do I connect the 2 wires from the 07 Grand Prix alternator to?

Thank you for your help as always,
and I'll try to not let it happen again.

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1999 Bonneville SE with the heart of a 07 Grand Prix

Or a starting point for now, I guess would be the FSM for 99 (SE) the schematic for the alternator wiring. The page that would show the 2 wires going into the back of the alternator.

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1999 Bonneville SE with the heart of a 07 Grand Prix

don't have 99 FSM. here is 96 FWIW.

Thanks GMman, it's a start. I'd like to be able to make this work. I feel like I'm so close but just not quite. If not I guess I'll just have to spring for another 99 style alternator.

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1999 Bonneville SE with the heart of a 07 Grand Prix

I made a 05 alternator work in my 91 silverado. But we didn't use but one wire since my truck only has one besides the power cable

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2000 ssei gone but not forgotten

Current fleet:
2009 G8 v6, 2009 Avalanche LTZ, 2013 Volt

Some pictures for now, still working out the wiring details.

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1999 Bonneville SE with the heart of a 07 Grand Prix

All right I give, ended up going the normal route and gave up trying to figure out how to get the car to see the 07 alternator voltage. Ended up getting a lifetime warranty one from Napa for 105$.

One thing I did do that helped increase voltage a little bit was adding a sense wire to the alternator connector(thanks 95naSTA for the idea). I found that the 96-99 style (might be a few years back covered to) alternator had sense capability but the cars weren't wired for it. It allows the alternator to see voltage drop happening and kick it up a little.

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1999 Bonneville SE with the heart of a 07 Grand Prix

FWIW, 00+ have a sense wire built in. It's a very nice feature, but it can't make the alternator give more than it's rated for, for anyone reading this in the future. A 120 amp alternator can only give 120A, sense wire or no.

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Bye Bye:

RIP sandrock

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1999 Bonneville SE with the heart of a 07 Grand Prix