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05 Pontiac Vibe with Electrical Issues / Low Voltage

So starting a couple of weeks ago I started experiencing some electrical problems that were pointing to the alternator. The lights on the instrument panel and headlights would dim when certain systems would pull more current such as the brakes or AC Fan.

After getting to the point where the radio would shutoff everytime I pressed the brake pedal I brought the car to an auto parts place and had them do an electrical diagnostic. Everything checked out okay except for the alternator voltage. I went ahead and replaced the alternator.

After replacing the alternator the issues went away and using a multimeter I was able to test the voltage coming from the alt. during load and everything looked good. I was able to bring the old alternator in for a bench test and the tech there told me that it wasn’t holding a charge.

It’s been two days since I changed the alternator and now more electrical problems are starting to show. This morning I noticed the airbag light was on and the flickering on the instrument panel started occuring again. Now the battery light is also flickering constantly while I’m driving.

The car has close to 90,000 miles on it so there might be something else that is failing that ended up killing the old alternator.

Could these problems be due to a failing belt tensioner? Could a loose belt cause these issues through the entire RPM range?

I know that there is a pending recall on the ECU for the 05 Vibe, could the computer be causing any of these issues?

I’m just trying to figure out where to go from here without replacing a whole bunch of parts that might be unrelated. I haven’t taken it into a mechanic yet so I might have to just go ahead and do that.

How old is the battery?

Maybe a bad ground strap. Not familiar with Vibes but all cars have a grounding strap running from the body to the motor. Maybe yours is loose. Look around in the engine compartment for a thick wire like a battery cable, that goes between the block and body. If it’s corroded replace it, or maybe just try a jumper wire for a day and see if it makes a difference. Any thick copper wire from the engine block to the car body will work. If it’s just in the instrument panel, you might try another grounding wire between any metal part in the panel to the car body. It really sounds like you have a grounding problem.

DC current can play tricks on your system. Electricity flows from a higher to lower potential. Usually that’s hot to ground but if there’s no ground then a lower voltage becomes that lower potential and electrical things start acting weird.

Another area to have someone check is the voltage regulator, although your symptons don’t suggest it, you never know.

Also, alternators don’t “hold a charge”, only batteries do that. Maybe he meant the alternator wasn’t working.

Since you say the lights are flickering it sounds like the replacement alternator now has some bad diodes in it. You are most likely going to have to replace it again. You should have a warranty on it. When output diodes fail inside the alternator it causes the output to have excessive ripple voltage which can cause the lights to flicker.

The new problem could just be a coincidence but it would be good to have the charging system checked out when the replacement alternator is put in. The shop needs to make sure that the alternator charging current goes down along with the load on the system and isn’t overcharging the battery. Certain faulty wiring conditions can cause the alternator to over work and fail.

The battery is from 08 and when the car is off it shows a charge of 12.8V. They tested the battery and started before I took the alternator out and both tested good.

I’ll look for the grounding strap and try using the multimeter on some of the wires in the systems to check for shorts.

Correct me if I’m wrong but in my car I think the voltage regulator is inside the alternator. I guess it could be the wiring harness too.

Sorry about that, he was just a sales guy but I think he meant that it wasn’t producing anything.

I was able to do some more checking with my multimeter and it was staying around 14.4V when under a load and revving the engine but it dropped around <13V when I applied a load and let it idle. I just drove it around for my lunch hour and it ended up stalling a couple times and the lights were still flickering. I stopped and shut the car off, turned it back on and it started acting mostly normal again. I checked the voltage coming off the alternator and it was still low during idle.

Thanks for the help, I’m going to go ahead and drop it off at my mechanic’s shop tomorrow morning. I don’t have enough time till the weekend to get it fixed and I want to make sure it doesn’t kill the battery or something during the work week.

Doing a full output load test on the alternator will show if any of the diodes are bad. The battery may be weak also and need replacing.