Alternator problems...or not?

_HighVoltage_

_HighVoltage_

Captain Volvo
Joined
Aug 5, 2006
Messages
9,964
Car(s)
1998 Volvo S70 T5M
For the past few nights I've started to notice something weird. 20 seconds after I start the car, the headlights seem to dim a little bit. It only does it one time - they don't fluctuate.

I have no other problems or signs - no warning on the dashboard. Everything electric works. The battery doesn't go flat.

I'm going to check the voltage tomorrow (should 13-14V right), but I just wanted to know - does it seem like a problem, or is this something normal? I can't say that the lights go terribly bad, they still work pretty good, I just can see the change in brightness.
 
Does your engine start to idle down after 15-20 seconds?
 
If it's slightly cold outside my truck will do that when it firsts starts, but it's just the grid heater cycling on/off until it gets warmed up. Do your lights go dim and then go back bright after a while or just dim and stay dim?
 
Spectre said:
Does your engine start to idle down after 15-20 seconds?
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No. It idles consistently at 900rpm - no fluctuation at all. Of course when it's really cold it starts at 1100rpm, but it's not doing it now, because it's fairly warm now.

MrNailhead said:
If it's slightly cold outside my truck will do that when it firsts starts, but it's just the grid heater cycling on/off until it gets warmed up. Do your lights go dim and then go back bright after a while or just dim and stay dim?
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They stay "dim"...but like I said, they are not dimmed badly.
 
do you regularly start the car with AC or defrost/ any other electrical load on?

If I start my car those things don't really kick in and start to load up the alternator until about 10 or 15 seconds in. Other than that I don't have a clue but it doesnt sound like the alternator has any problems.
 
No AC...just the stereo.

It could be a result of the air pump that sucks in air into the engine in the very beginning.
 
That air pump doesn't start until the engine does.
 
if it was an alternator problem you battery would slowly die and you would only be able to drive as far as your battery is charged then die again...its probably just the early load on the car and if anything would be your battery going bad...if it isnt holding a charge as good as normal then in the beginning after start up it will put a load on the alternator but once the car charges the battery up then it should be fine.

try leaving the car off for an extended period of time like a day if possible and then go to start it and see if the problem is worse then before
 
Spectre said:
That air pump doesn't start until the engine does.
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That's when the lights dim. They don't dim if I don't have the engine started.

Boomhower said:
if anything would be your battery going bad...if it isnt holding a charge as good as normal then in the beginning after start up it will put a load on the alternator but once the car charges the battery up then it should be fine.

try leaving the car off for an extended period of time like a day if possible and then go to start it and see if the problem is worse then before
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That's quite possible. I've had problems with the battery in the past. Leaving it for one week is not a problem. Anything more than a week and it goes completely flat.
 
Well, I checked the voltage and noticed something weird.

Engine not running - 16V
Engine running at 3000rpm - 18.5V

It could be a faulty multimeter, or the battery is messing up. But at least I know that the alternator is charging.
 
^ That seem a little high to anyone else? I think my cars typically run at around 14. I don't know if it's at all relevant, but in my old '83 VW rabbit diesel I used to have, I would have to periodically clean off the battery terminals as they would get coated in crud and it would have trouble starting or running with lights/stereo on.
 
how old is the battery? if it wont charge right then the alternator might be over charging it while running and the cells may be swelling up and losing their efficiency. Id take a different battery and put it in there just to see what happens...take one out of a friends car you know is good...it doesnt cost anything and if it fixes the problem then you know to replace yours...if it doesnt then its one thing to cross off the list and then you can try to see if the multimeter is not functioning correctly
 
Battery was manufactured January 2009, so I would say unlikely.
 
_HighVoltage_ said:
Battery was manufactured January 2009, so I would say unlikely.
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I think it's a battery issue. If your battery is going flat after a week, its not good. I had a brand new optima dry cell battery do that. I took it to get tested and it was bad. Replaced it with a new one and I don't have those problems anymore. At the very least, take it to an auto parts store and have them test it, it doesn't take 5 minutes and it's free.
 
I'll do that today.
 
I went to Autozone and had my battery and alternator tested. The alternator is charging fine. The battery is producing 12.54V

So everything is normal. I must be imagining things.
 
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