1995 Bonneville Alternator Replacement
I was fairly certain my alternator was going bad when I heard arcing in the alternator and my volt gauge was showing about 10 volts. Several months ago, a couple of times I went to start the car and it would not turn on. I thought it was a slow leak somewhere or just a weak battery. Since I couldn’t find any detail on the Internet about this topic, I thought I’d try and post something here.
You will need a new alternator, a 15MM socket and a 13MM socket, WD-40, tape, some latex gloves, pencil, tablet of paper, and a favorite candy bar.
1. Always safety first. Disconnect the red power cable from the battery.
2. Take a picture or draw how the serpentine belt goes around each pulley. This drawing is also in the Pontiac manual but the manual also includes an extra pulley that was not on my car.
3. There are 2 wires that attach to the alternator. One is a single 14 gauge red wire. It has a plastic clip at the base that you need to lift in order to take off the wire. The other is a larger wire that comes from the battery. There is a plastic cap that just pulls off where it meets the alternator. Use your 13MM socket to remove the nut attaching the wire.
4. As you remove nuts and bolts, find a safe place where you won’t knock them, and place them in the order you removed them. Then write down or draw a picture of where each one goes. I tend to have left over parts when I do a project like this and this helps make sure all the pieces go back to where they started.
5. I use blue painter’* tape. Tear off a few pieces and tape the belt to the pulley. This will keep the belt in place when you take the tension off the belt and help you from trying to route the belt from scratch when you’re finished with the alternator. There are several pulleys and I did this to about 3 or 4 of them.
6. Now, the fun part. You need to relieve the tension on the serpentine belt. There is one pulley on something called a tensioner. It is located about the 5 o’clock position under the alternator. I was apprehensive about doing this next step as I didn’t want to break any bolts but this is the only way to get the tension off the belt. Take your 15MM socket and place it on the nut holding the pulley on the tensioner. Now turn the nut CCW like you’re trying to take the nut off. It has a reverse thread on it so you will not take the nut off. Put some muscle behind it because it has a very large spring. You need to move the tensioner about 2 or 3 inches to get enough tension off the belt, now slide the belt off the pulley while holding the tensioner down. Slowly let the tensioner back up and careful not to disturb the belt too much.
7. There is a bracket that runs under the coils to the alternator bold at about the 2 o’clock position. Use your 15MM to remove the nuts and take off this bracket. Mine was a bit tight and scraped the threads on the bolt but no major harm done. The same bolt on the alternator has another nut on the same bolt and you’ll need to remove this bolt/nut combo.
8. Remove the bolt on the alternator about the 11 o’clock position.
9. Remove the bolt on the alternator about the 6 o’clock position. This one is kind of hard to see. Be sure to unscrew this one because the water pump bolt is close to it. It helps to lift the alternator just a bit while unscrewing it.
10. Carefully pull out the old alternator.
11. Carefully put in the new alternator.
12. Reverse these steps to install the new alternator – EXCEPT – step 6 – still go CCW (not CW) to get the belt back on the tensioner. Be sure to check the belt before and while you’re putting it back into place. It is a grooved belt going into grooved pulleys and getting it skewed out of track will destroy the belt. Make sure you get 2 cables back on the alternator and one back on the battery.
13. Double check all your connections and screws. Get tools and stuff out of the engine area. Start the car to see how you did. Check you volt gauge which should read between 12 and 14 Volts. Check the engine area and do a visual and hearing check. If you did something wrong, you’ll know in a hurry since there’* a lot of power in that V6. Let it run a few minutes and do a smell test also for overheated wires or the alternator. Just because it’* new doesn’t mean it can’t be bad. If everything checks out, close the hood, turn off the car, put the tools away, go get your core charge for the old alternator, and have that candy bar.