An Electrical Problem

[LifIsPeachy02]

Hi, i am not new to these forums and have been a DSM'er for awhile now. I have a 1995 Mitsu Eclipse GS-T. There are no major mods.

Anyway, i went out to my car to leave the other day and it was just BARELY dead. It was just dead enough it would not start. It would barely crank. I tried to jump it off a friends car and it wouldn't jump. I went and bought a new battery and installed that. It fired right up, and, believe it or not, it ran better than it had in a long time. The idle was a little goofy, surging a little bit. Now, its back to running like it was before, the headlights and dash lights dim and brighten for about 5-10 minutes after the car is running, maybe more. For a few minutes after it I start the car a few dash lights stay on. The lights that stay on are the break light, the coolant light, and another light i forget what it is, maybe the battery light. I was suspicious as as to if this was a bad alternator. I don't know though, maybe even a bad ground. What do you guys think? I am clueless most of the time with electrical problems.

 

[luv2rallye]

Most likely bad alternator or 100 amp alternator fuse blown. Measure voltage at battery with engine running - should be more than 13.5V.

 

[blcknspo0ln]

I suspect your alternator is shot. go to autozone, they check it for free

 

[steve]

It seems stupid to pull an alternator and take it somewhere before you do some simple diagnostic testing in the car.

Like luv2rallye said, start the car, measure the voltage at the battery and at the alternator.
Since the ECU on a 2G turns the alternator off when it's not really needed it might help if you not seeing 13+ volts to try turning on the headlight and HVAC blower.

The next thing to check are the various fuses in the alternator circuit. There is the 100A bolted in the fuse box (#1) that fuses the charging current and a 40A fuse (#5) for the field coils. Don't just look at them. Check for voltage on both sides of the fuse or pull them and measure their continuity.

I don't know how the 2G alternator fails but I suspect a lot of them are due for new brushes.

Steve

 

[Ultimatedsm]

Yeah I had about 5-6 fail one me. Now my recent alternator has been really good, what was the difference? Never buy a rebuilt alternator, go to mitsubishi. The rebuilts would last around 2-6 months, where this one has been going over a year now without any problems. Does your dash flicker? ex: engine light, parking light etc. Thats a sign for a bad regulator in the alternator.

 

[Old Mitsu Tech]

An alternator can fail in several ways. One way no one thinks of is it's putting out too much ac voltage. Using a multimeter on ac volts. Check across the battery. If you have over 400mv ac voltage the alternator rectifier is bad. This accounts for some of the alternators checking good on dc volts but still not working right and the dash lights and gages acting weird.

Good Luck

 

[LifIsPeachy02]

Thanks for all or your input. How much does an alternator cost from Mitsu?

 

[BoostinAWD]

I had the same problem on my 91 tsi fwd. Changed the alternator fuse. Works great now

 

[luv2rallye]

How much does an alternator cost from Mitsu?

VERY PRICEY! I have found it is not worth the tradeoff. Although a rebuilt can never be as good as a new one, they work fine if you get them at a place that only repairs/refurbishes alternators and starters for shops and dealers (don't get them at an auto store unless you have to). These places replace the bearings and diodes as well where other places don't always. You can also specify you want a rebuilt factory alternator there (you never get factory at an auto store). If you want a new one, you can get them here as well for much less than Mitsu. Whether new or rebuilt, they all come with a warranty anyway should it fail.

 

[steve]

I second the idea of going to a automotive electric shop. When I can't fix an alternator myself I take it to my local shop and let them clean it up. They will test the field coil and stator for shorts, check the diodes and regulator, replace the bearings and brushes.

I've had much better luck doing this than picking up an alternator from any of the auto parts stores.

Steve