It could just be in my head, but I swear that my headlights got a little brighter when I hit the accelerator. The car just came out of the shop on Friday, after the alternator and battery were replaced. I don’t recall it doing this before then. Is this… normal for a car that’s just had the alternator replaced?
Could be that the alternator isn’t charging quite right.
You should have about 14.4 volt on the battery post with the car running, pretty much at any speed. It may vary some but shouldn’t really be affecting the lights.
It could be a bad connection too, though.
This could be something as simple as a low idle or a battery that is on its last leg. Sometimes a bad battery is misdiagnosed as a bad alternator, and sometimes it’s the other way around. You might consider getting a second opinion and having a different mechanic test your battery and charging system.
Even though they are new, have the shop double check the battery and charging system. Even new parts can be defective.
This could happen if the battery is not fully charged. Some of the current may be going into charging the battery, and when you step on the gas, some extra current becomes available for the headlights. But once the battery is fully charged, no current is necessary to charge the battery, and the alternator can put out plenty enough for everything else, so there shouldn’t be much difference in the headlights at higher rpms vs idle.
The new battery may have been only half charged when they installed it. Common if it has been sitting in a warehouse for 6 month prior. If the headlight problem persists after a month of driving, take the car back and ask them to load test the battery and the charging system.
Whitey:
This could be something as simple as a low idle or a battery that is on its last leg. Sometimes a bad battery is misdiagnosed as a bad alternator, and sometimes it’s the other way around. You might consider getting a second opinion and having a different mechanic test your battery and charging system.
Well the battery is brand new, just got it installed last Wednesday. Alternator is new too. You may be right that the bad battery was misdiagnosed as a bad alternator. That battery was in there for 10 years and 115,000 miles; it was due. BUT… the car wouldn’t start at all. I couldn’t even get it jump started. Consequently, I had to have it towed to the mechanic. Once it was there, it wasn’t moving without another 75 bucks for a tow. So they sorta had me over a barrel.
GeorgeSanJose:
This could happen if the battery is not fully charged. Some of the current may be going into charging the battery, and when you step on the gas, some extra current becomes available for the headlights. But once the battery is fully charged, no current is necessary to charge the battery, and the alternator can put out plenty enough for everything else, so there shouldn’t be much difference in the headlights at higher rpms vs idle.The new battery may have been only half charged when they installed it. Common if it has been sitting in a warehouse for 6 month prior. If the headlight problem persists after a month of driving, take the car back and ask them to load test the battery and the charging system.
This was my thought as well. Like I said, the alternator and battery were just installed. I’ve done maybe 20 miles of driving in total since then, all of it in the daytime until tonight when I had to drive out to the store down the road to get some milk. I wanted to get some extra opinions.
So I only drive the car about 70 miles a week. Am I correct to assume that the battery will only charge when the engine is running? Do you think a month of driving (about 280 miles) will be enough to get this battery charged?
It sure should be. If it isn’t charged by now, something is wrong.
I once had a car that seemed to go through alternators frequently. After paying for three alternator replacements, it ended up being a cable that connected to the alternator. When the car was first started, everything was fine, but after a while, that cable would heat up and stop conducting (or not conduct as well). You might simply have a loose connection or a cable that needs to be replaced, but you will need a mechanic who is good at troubleshooting electrical problems, and they (both electrical problems and good troubleshooters) are hard to find.
I forgot about this. What turned up being the problem was that the cable that connects to the passenger’s side headlight was loose. Over time, it came completely disconnected and the headlight was completely dark. It was when I tried to replace the bulb that I noticed the disconnect.
Thanks for reporting back. We often don’t hear a thing.
It is good to see you got to the bottom of it and it didn’t cost you anything.
Hey, is there a make and model for this vehicle? I have a 2007 Saturn Outlook doing the same thing. It had check charging system come up on the DIC, I tracked it to the alternator, changed the alternator out with a remanufactured Auto Zone alternator. Ever since my headlights and interior lights randomly get a bit brighter or dimmer.