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Alternator Issues

So my galant died on me this weekend. Towed it home and started running some tests. After I charged the battery back up and started the car I was seeing 14v for about a minute and then it dropped back to 12v. I pulled the alternator and swapped one from my 1g Laser and started the car up. 12v. Pulled it out and took both down to kragen and they both passed. Im trying to find out if someone has a copy of the alternator circuit diagram because all I have is the 1g DSM one and I am not sure if its exactly the same(Like L terminal running through relay and indicator light). With the key on engine off Im seeing 12.5v(+Bv) at the S terminal, but only 11.2v at the L terminal. Is this right? Or should I be seeing 12.5v at L as well?

I ran a resistance check between the L terminal and the terminal at the alternator relay and there is no readable resistance value. I want to check the other half of the L circuit to see where I am losing Voltage. I also checked the B terminal circuit and there is no resistance between it and the + battery post. I am not sure where to look next and its a little hard for me to think that I have 2 bad alternators that both passed the part store tests.
 

raptorWagon

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Joined
May 17, 2007
Messages
2,827
Location
Oak Harbor, WA
So you know, the alternator off the 1G is a lower amperage than ours (Galants have 90 amps, 1Gs range from 65-75amps) and that can offset your troubleshooting some as well.
 
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Yes im aware of the AMP ratings but I have the ABS and AC deleted with stock stereo so That is of no worry to me and shouldnt interfere with my tests. I should no matter what be seeing 14v+ at idle upon initial startup. I just went out and tested my roomates 93 GSX. With his Key on Ignition Off I got the same values as my car. From what I can tell by reading the circuit diagram, by having correct readings at the L&S terminal connector I can only assume that BOTH alternators are somehow faulty. My roomates car with the harness unplugged jumped to an unregulated 15v. On my car both alternators would stay at 12v with the plug connected or disconnected.
 

prove_it

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Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD
there is a fuse that protects the charge back wire. Check your voltage readings at the output terminal on the alternator. could be in the chargeback wiring, or a blown fuse.
 

misterfixit

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Joined
Aug 4, 2004
Messages
1,596
Location
Midlands, UK
check the earths back to the body and engine are good. if the negative cable off the battery back to the body gound is shite you'll be chasing gremlins for ages. mine was crusty as hell and it was the last thing i looked at.

Rich
 

Well I 2 weeks ago I went ahead and just replaced the alternator with a rebuilt autozone one. Not a single problem since then. Its just weird that 2 bad alternators would pass the tests.
 

I've experienced the false pass on alternators before as well. My belief is that the checker/schucks/kragen bench testers miss something when tested our alternators. My suggestion is always have your alternator tested at a napa parts store.
 

TurboTrader

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Joined
Jan 30, 2009
Messages
161
Location
Pemberton, NJ
That, and that Autozone and Advance Alternators are absolute garbage. They are remanufacured units, and not re-manned very well at all. I've had and heard of bad luck with them across the board. Not only in VR-4's/DSM's, but in my sister's Maxima as well, none have worked well for more than a few hundred miles in my experience. After getting a bad one from Advance for my DSM, I got an OEM unit from a 93 Galant (90 Amp), and it still to this day works great. The advance unit lasted short of 7-days before I noticed my lights were brighter than normal, and in my gearhead fashion knew something was wrong. It was pushing a solid 15+ volts when the regulator died quick. The unit in my sister's Maxima had the opposite problem where it was not charging properly (alternator, again), and I replaced it with a Napa unit, 6-months later haven't had to mess with it again, thank God. I also have a friend that had an Autozone alternator in his DSM and it blew up both headlights as well as causing other misc. electrical damage. He was furious and they wanted to do little more than replace the faulty alternator to which he agreed. Second alternator, same thing, and they re-funded him after much fuss on his part.

Point is, Napa seems halfway decent, but I still love OEM alt's if at all possible.
 

AnotherNewb

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Joined
Apr 25, 2010
Messages
1,472
Location
Orlando, FL
Off topic but... I once had 3 starters in a row from A/Z that didn't have the brushes soldered on. /ubbthreads/images/graemlins/banghead.gif
Guess someone hated their job and wanted to make their last day memorable.
 
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