Wierd electrical problem - charging system

[DGajre777]

I got my 60k timing belt service done at my local Mitsubishi dealership about a month ago and replaced the harmonic balancer and the alternator belt. The battery is 2 months old.

This is what happens. I start my car, sometimes the battery light and brake light comes on. If I move forward and make a left or right turn the lights turn off. Once the lights go away, they don't come back again the whole time I drive.

The only voltmeter I have is in the trunk in my amp and it reads 13.5 volts under normal conditions. When the battery and brake light comes on, it reads 12.0 volts. I ordered a Stinger voltmeter, it should be here in the next few days. I took it to Advanced auto and the guy hooked up a voltmeter and said that it was charging good (which I knew cause of my voltmeter in the trunk).

I know the lights mean normally mean a dead alternator. I also know that if the volts is not stable it means that the voltage regulator in the alternator is bad. What could this be? I'm thinking that is it more of a connection problem instead of an alternator problem. The last thing that I want to do is get a $200+ Mitsubishi alternator and have the same problem.

Any ideas?

 

[blackbyrd]

Hey, a few more things I would check out. The battery voltage when its off. A fully charged battery should be around 12.5v. Check to see if it's draining or anything. Check for shorts.
I believe a good output on the alternator is over 14v.
When it jumps down to 12 do your rpms drop or anything else happen?
Have you doulbe checked the tension on the belt?
I would say it's probably your alternator. You can get a mitsu, they're still just rebuilt alternators. Try to stay away from advanced auto/auto zone. You could have a reputable shop rebuild yours. If you want brand new the only ones i know about are some of the HO alternators. Just make sure you get a warranty!
Good Luck!

 

[silvercoupe97]

Check the two fusible links. Make sure the bolts that hold the fuses on are tight and have a good connection. Test the two fuses before you start the car, both sides of both fuses should have battery voltage at all times (this is assuming that the battery light will be on again). Make sure the alternator power wire is tight. Go by the book and check the alternator. You can even do it this way.
I just went through a similar issue.
Get a digital voltmeter, their not that expensive.

 

[fulanititoo8198]

it's funny you mention your problem because my car does the same thing and I took the alternator to get tested and they say it's good. I'm swapping my alternator I'll let you know if that fixes it.

 

[silvercoupe97]

Oh one more thing. Do you notice if your interior lights light up when you open the door? If not, then it will be the fusible link area. I don't know if there is a relay around there, but when mine was acting up, I could hear a click in that area and my interior lights would come back on.

 

[DGajre777]

When the volts go down to 12v, everything works the same, no change in RPM, just the lights come on.

I haven't checked the tension of the belt, I figured Mitsubishi mechanics knew what they were doing.

Are you sure Mitsubishi alternators from the dealership are rebuilds? I thought they were new?!

 

[blackbyrd]

Nope, I've been told by jnztuning that they stopped making new ones in 1998. But, I'm pretty sure they tell you there new! haha.

 

[DGajre777]

Well, I checked my fuse, it is fine and bolted in. My Stinger digital voltmeter came in today, so I installed it and went for a drive around town.

Here are the results:
Before start up - 12.0-12.2v
After start, at idle - 13.2-13.6 volts
Driving around town - 13.2 to 13.8 volts
With audio system on, headlights on and AC on at idle RPM went down to 11.6v once, then 2 seconds later it went up to 13.6 after I raised the RPM
Cruising at 2600-3500RPMs - 13.7-13.8 volts constant

It seems that my charging problem is only when my car RPM drops down to idle. Once I get out of idle, it charges fine. I am getting the alternator tested sometime this week, I know it is probably shot.