This is my first post to this board, so please bear with me as I try to relay all the information that might be needed. You guys have provided some great information in the past, and I'm hoping to have some more luck! Here it goes:

I have a 1993 Bonneville SSE (approx 132k miles) that is exhibiting some strange behavior. Here are the symptoms :

• Battery (voltage) gauge will drop to approximately 12 after the car warms up to operating temperature.
• Battery doesn't actually drain - I haven't needed to jump the vehicle, and all accessories will work when the voltage gauge is lower than expected. It doesn't lower the gauge any further when I have the accessories on.
• The check engine light will come on when the voltage drops. It only comes on when I apply the brakes, and then turns off when I let off of them.
• The temperature gauge has been going all over the place - I have replaced the thermostat (put in a 180) and water pump within the last 6 months. The engine does seem to be overheating though.
• The cooling fans do not come on as expected - I have replaced both relays for the fans in the past 3 months.
• When I'm idling with the brakes on, my RPMs will waiver between 500 and 700 - when the headlights are on, there is an obvious drain on the electrical systems (I can see the headlights dim, and then come back up.

I had the alternator tested at Advanced AutoParts, as well as using a battery charger/tester. Advanced indicated that the alternator was not receiving any power and therefore not producing any power. The battery charger/test indicated that the alternator had failed. Both tests were conducted when the voltage was around 12.

As I indicated before, I've changed the water pump, thermostat, and both fan relays within the past 6 months. I've also changed all spark plugs and wires, as well a headlight assembly (stupid deer). Lastly, I had the timing sensor (forgive my lack of specificity here as I don't recall the exact name of the part) changed back in September.

Any help you could provide would be amazing - I really don't want to have this thing taken in for an electrical diagnosis, and I'm hoping that you all will know something that I don't.

Thanks!

Have you checked both ends of both battery cables for corrosion?

There is also ground connections attached inside of both fenders. Look there to for corrosion as well.

Check into this to:

https://www.gmforum.com/t278980/

Also pop off the connector to the alternator and see if there is corrosion there to.

-Todd

Start with your grounds like Todd suggested. Those can cause problems like you discribe.

If you feel up to it, take out your dash instrument cluster and pull out your right three gauges and check for corrosion on the back of the board where the pins push into the cluster. This would cause the gauges to act crazy if the pins are all corroded.

Oh and We welcome you to the Forum!!

-Todd

-Dan

They said it above but I had very odd issues way back with my 94 SSEi shortly after I purchased. It was estate sale and was sitting for a while.

I would literally hit a bump and the engine would shut off and then restart while coasting.
sometimes start and other times no crank at all ... then start as no issue 20 seconds later.
some ghost.

After I cleaned the battery cable contacts (like crazy) I never had issue again (near 80k miles after that).

Good Luck.

PonchoPete
2005 Bonneville GXP – Dk Grey
2001 Grand Prix GTP
1994 Bonneville SSEi – * Port Magnuson SC
1969 Grand Prix SJ – 428cid/370hp

Thanks for the info - unfortunately, I haven't had a chance to check the ground bus for corrosion, but it'* on my list for this weekend. I think my alternator actually died so I'm going to take it into an auto parts store and have it tested.