Alternator Overcharging

[tsunari]

So here's the deal:

Bought a 1g AWD about 4 months ago and have noticed several little quirks that need to be worked out. The one mentioned in here is this . . .

While driving, I've noticed that randomly (more usually when the motor is hot) the headlights, dash lights, etc will momentarily brighten a LOT and then dim back down to normal. When the lights brighten, it feels as if there is an extra load on the engine (kind of like when the A/C kicks on).

I finally got over being embarrassed about how filthy the engine bay is from the previous owner and just took it to AutoZone to get the battery and alternator tested.

Battery checks out OK
Alternator checks out OK

HOWEVER- while the alternator was being tested, the lights happened to go bright again and it was putting out roughly 17-18V. I'm thinking that probably the built-in regulator is shot and thus occasionally overcharging the system. (BTW- the diode pattern checked out OK as well)

Anyone agree/disagree?

 

[92awddsm]

I agree

 

[plymubishi]

Sounds correct to me as well

 

[tsunari]

Cool, just wanted to double check before picking one of these things up . . .
the ones at AutoZone good? Or should I hit up a junk yard or maybe even the dealership?

Picked one up from AutoZone for $100 . . . just hope the current one will last until I can get it changed out. Something is starting to smell like rotten eggs- battery perhaps? (I sure hope it's not the ECU . . . I hear that smells like fish though)

Replaced the alternator and battery- all seems to be well now.

 

[plymubishi]

Good to hear it worked out for you without a trail of other things

 

[steve]

Alternator checks out OK

HOWEVER- while the alternator was being tested, the lights happened to go bright again and it was putting out roughly 17-18V.

I know that you replaced the alternator and for the moment the problem is fixed.

What I'm wondering is how anybody could have said that the alternator was ok if you were seeing 17-18v while testing?

In my book that would have been a failure.

Steve

 

[tsunari]

You've gotta keep in mind this was an AutoZone employee running the test
The machine didn't say one way or the other if it passed the voltage output . . . it just happily displayed what was being pumped out of the alternator (which happened to be 17+V).

Every other source I've looked at says that anything over like 15V normally points to a failing regulator. So I'll keep an eye on things and see how it goes

 

[92dsmtalon]

So here's the deal:

Bought a 1g AWD about 4 months ago and have noticed several little quirks that need to be worked out. The one mentioned in here is this . . .

While driving, I've noticed that randomly (more usually when the motor is hot) the headlights, dash lights, etc will momentarily brighten a LOT and then dim back down to normal. When the lights brighten, it feels as if there is an extra load on the engine (kind of like when the A/C kicks on).

I finally got over being embarrassed about how filthy the engine bay is from the previous owner and just took it to AutoZone to get the battery and alternator tested.

Battery checks out OK
Alternator checks out OK

HOWEVER- while the alternator was being tested, the lights happened to go bright again and it was putting out roughly 17-18V. I'm thinking that probably the built-in regulator is shot and thus occasionally overcharging the system. (BTW- the diode pattern checked out OK as well)

Anyone agree/disagree?

Ok, hate to bring back such an old thread, but this is everything my 2g is doing, minus the batter charging up to 17-18V, mine is staying at around 14.08-14.20, everything else though is the same...any ideas?

 

[steve]

Since an output of 14v is fine what's your problem again?

 

[92dsmtalon]

Because all my dash lights, head lights, are getting really bright like they are being over charged, but like I said, the battery isnt being over charged. Im having the exact same problems as "tsunari" did, just without the overcharging.

 

[steve]

If your measuring the voltage in the car and it's not going over 14.6 volts then you don't have a overvoltage problem. You might have a problem that the alternator doesn't put out enough voltage at low RPMs and so it seems like the lights are getting real bright but in fact they are just dim before.

Either case you need to measure the electrical system voltage under different loads to see if you have a problem and what sort of problem it is.

 

[92dsmtalon]

Ive been told a few times it could be my voltage regulator. but, i know for a fact they are getting bright, and dimming back to where they should be. it just confusses me because the highest volt reading ive gotten was 14.20.

 

[steve]

On all Mitsubishi powered DSMs the voltage regulator is in the alternator.

If you measure the voltage in the car, while driving, from something like the fuse box by the driver foot or the lighter socket and it doesn't go over 14.6v then you can be pretty sure your not seeing over that anywhere else in the car. Since the ECU has some control over the alternator output on 2Gs (different forms but on all 2gs) it's possible for your system voltage to drop to 12v or so when the ECU turns the alternator off.

The lights will change brightness quite a bit between 12v and 14v but that's not a problem per say.

 

[92awddsm]

Do you have a logger or turbo timer that displays voltage? If so, keep an eye on it when the brightening happens to see if the voltage output spikes at the same time. When Matt's(tsunari) lights would go bright, it was when he was cruising down the road at a steady rpm without getting on it or revving it.

If yours goes bright and then dim again while putting out a steady 14.9 or less volts at a cruising rpm, I would begin to start checking all of your grounds. You could possibly have a poor ground that happens to work occasionally.

 

[JayRolla]

Yea the regulator in the alternator is bad just like the other guy, swap the alternator and your issue will be fixed.

 

[92dsmtalon]

Yeah, I think Im going to end up swapping the alternator. It is spiking all the time, not jsut when im cruising...Yesterday I noticed that my temp gauge would skyrocket too when the lights got bright, and would go back down when the lights dimmed back to where they need to be. My dad has a buddy who owns a local shop that rebuilds them, and he said that he could do a more extensive test on the alternator, so Im hopefully going to get an answer from tests later today. Thanks for the help, and Ill let you know what the end issue/solution is.