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1G Low voltage while running/WOT

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19gsx91

10+ Year Contributor
1,199
294
Apr 20, 2011
Walworth, New_York
Hey guys, I'm posting this at work so I'll attach a log when I get home..

Basically what's going on is my battery output while off is the usual 12.4-12.5 volts.. but while running it only goes up to 12.9-13volts.. constant. WOT is normal, it will drop down a little bit throughout the pull but what could be causing the voltage to be constantly low like that? Battery is good, alternator was changed a few months ago with a 90amp galant alternator. If I add a load such as fans, or lights it will dip down but then go back to 12.9-13.0v

I'm suspicious of the alternator but this will be the 2nd or 3rd time I've installed one in the last year or two and I want to make certain that it is the issue and there isn't some fusible link somewhere that has just deteriorated over time.

My next step is to check voltage at the alternator while running, is there anything else I should be looking for?

Thanks,
Joe
 
Joe, check the voltage at the alternator terminal then recheck it at the battery. If there is any loss, add an extra charging wire in addition to the original or replace it all with one good, big wire. Heck you could just run any random wire over to the battery as a test to see if you get more voltage to the battery and car. Is it grounded good? That is something that some people over look so make sure it has a very good ground from the battery to the engine/trans/firewall etc.
I also run the Galant alternator and recently went to LED lights, where I could, to keep the voltage up on the injectors and ignition.
 
This can still be the alternator but the wiring problem (either connectivity or corrosion in the wiring itself) can definitely be the issue as well. Both are very common, the latter due to the age of our cars. Many alternators don't come out of the box working for various reasons (shitty re-man, shitty packaging resulting in damage, who knows what else).
 
I'll double check these when I get home tonight, kinda hard to get to the charging terminal on the alternator because of the EWG but I'm sure I can figure something out LOL.

TBH Marty I never thought of the ground. I will investifart the grounding situation.

John, I know what you mean about new alternators not working.. I went through 3 or 4 in my 83 Camaro (45 amp? and it still wouldn't work!?) before I gave up and ordered an aftermarket 1 wire.. I keep hoping I'll get lucky with these parts stores but it never seems to happen.
 
So true on parts store stuff. If I buy local, I buy the lifetime warranty items so if it gives up the ghost, I go get a new one. I have been pretty lucky so far with my Galant alternator from O'reilly's but I would bet it will fail far before a factory, or a good rebuilt one, will last. I used to rebuild them (gm and ford and chyrsler) but it is hard to find the rectifier, diode trio, regulator and brush set for a lot of stuff now.
 
I went through 2 auto zone alternators in 1 day as they were not charging right out the box. Said screw it and pulled one from a 96 Saturn from the upullit for 25 bucks and has been running strong every since. Nothing below 13.5v and stock wiring to battery.
 
So true on parts store stuff. If I buy local, I buy the lifetime warranty items so if it gives up the ghost, I go get a new one. I have been pretty lucky so far with my Galant alternator from O'reilly's but I would bet it will fail far before a factory, or a good rebuilt one, will last. .
It gets pretty miserable constantly bringing back alts over and over to the auto store with their "free lifetime warranty" when you have to do all the replacement labor yourself over and over (and car is usually down during this). It makes the free lifetime warranty worthless when they keep breaking down or never even working right out of the box.
 
It gets pretty miserable constantly bringing back alts over and over to the auto store with their "free lifetime warranty" when you have to do all the replacement labor yourself over and over (and car is usually down during this). It makes the free lifetime warranty worthless when they keep breaking down or never even working right out of the box.
Yes that would be a miserable life, not that it's hard to do. I have been fortunate then and have never used the warranty on mine. Now if you continue to let the PS fluid drip into it and have the heat under the hood more than normal, that probably spells a recipe for failure. I am heat wrapped and it has helped bring under hood temps close to normal even though that car is FAR from stock. As I said earlier, if I could still get the rectifiers, brush set, diode trio and regulator I would always just rebuild mine. I have a hard time getting those parts though.
 
If I could marty I would've just sent you a crate of the alternators we pulled off the shelves a few months ago at my work.. probably 15-20 late 80s-99 mitsu alternators got thrown out because they'd been on the shelves too long, I didn't save any because they were all the low voltage ones.. but they may have been good for parts. there were a few remans.

I'm sorry I'm slacking on updating this guys, by the time I get home from work and let the car cool down I'm out cold.. two days now I've gone out to go to work in the morning and have had to shut the hood on the GSX because I left it up overnight "wanting" to go out and check the voltage.
 
Boy those would have had some salvage in them. I know how you feel on car work, at 53 my work decided I need to work 6 days a dam week and I am wore out to. Projects take a little longer than I usually anticipate. Hang in there, it will get fixed!
 
Lol yeah, Well I'm only 27 and between my daughter being born 4 weeks ago, owning 9 vehicles now, battling an auto auction on getting the PROPER paperwork for a car trailer, working 6 days a week babysitting man-babies, and still trying to find time/money to mod the DSM it's been a nightmare.

Please. explain to me how you hand a co-worker an interchange for a tailgate for a 97-04 dakota.. and they bring up a tailgate off an 06 and then shrug and tell me it's still a dakota so it doesn't matter right? ..I had a question to go with that but I got so frustrated thinking about that when I typed it out I'm out of coherent thoughts.

what bothers me the most is that we just had an 88 mighty max 4x4 5spd come through that was CLEAN and I come in late one day and they crushed it..
 
I should clarify my frustration with the mighty max though.. as hard as it is to find parts for our cars.. I imagine mighty maxes are way harder to source anything for. the yard paid 100 bucks for it, I could of taken it home, parted it out and brought the shell back and they STILL would of made money crushing just the frame.
 
That is how I figured the ONLY yard I could find with my TCU felt after I let them charge me 225 plus a finders fee then called me the NEXT day to tell me they crushed the car 2 days ago. Hell the car didn't weigh any more with the TCU. That was frustrating. Feel you man but you're young LOL.
 
@1990TSIAWDTALON Hey Marty, sorry it's been a few days.. I managed to get the eclipse in the air yesterday, 12.6 volts at battery. 12.5 volts at the alternator not running. I'm fairly certain it's a "cheap alternator" issue. I'm gonna dig up my reciepts and see exactly which one I got.. and move forward from there.
 
Yep Joe, that sounds like a bad unit. I hope you can get a decent one and have it last. If it is a parts store unit, have them test it before you even leave the place!!! At least you are making some progress. I was sick a few weeks ago and my energy after work is not like it used to be. I need to get my 2150's in and start tuning again, my 1650's are giving me some hassle so they are about to be removed and sent in for cleaning, I just gotta have time, and my farm says I don't have that time yet (dam 3 acre lawn, won't stop growing).:banghead:
 
For an alt forget auto stores, they're nearly all junk - and this has been EXTREMELY well documented here on Tuners by hundreds of people. Most test ok at the store but still will not work in the car. Get your alt at a starter/alt repair shop for a quality one that works every time (or you can have yours repaired there).
 
This^^^.....if you can find a shop. We don't have any local around here.
I have to wonder where those shops can get the repair parts because the rebuild is simple as hell. I was doing rebuilds of starters and alternators and generators in the 70's but parts are hard for me to find now. Anyone have any sources?
If a vendor could source these parts, we could all do them.
 
@luv2rallye Yeah, I got a reman'd bosch unit thinking I'd be safe but it was still a parts store special, I actually had to go into my build thread to find the rough date of when I changed the alternator to get the part numbers. LOL

The best I can do Marty is see if my coworker saved anything off that mighty max, and then I've got a spare OEM alt. So I've two I could send you.

You could contact Miller import parts. @Stangmurdera I believe he has a pile of 1g alternators.
 
I also run the Galant alternator ......

I figure you and 19gsx91 are talking about the M162836D 90 amp alternator.
Looking for alternators on oemmitsubishiparts.com I see this:

M162836D Discontinued.

But lower on the page they list a "Related" alternator:
M149750D 95 amp alternator, which they say fits only 1991-1993 Galant. $228. They don't list any Eclipses or Talons as compatible on that one.
Has anybody tried this M149750D 95 amp alternator on a 1g Talon or Eclipse?
 
Got any idea what the back of it looks like, as in the plug itself? Would be nice if it would plug and play but we all know we can just about make anything work if we want. I will see if I can see that part later today.
 
Got any idea what the back of it looks like, as in the plug itself? Would be nice if it would plug and play but we all know we can just about make anything work if we want. I will see if I can see that part later today.

Well guess what, I sent a contact form to oemmitsubishiparts.com late last night, and today I got an email back from them saying "If you can provide a VIN I can check the fitment for you, unfortunately this part is obsolete and no longer available to order."
And then I looked at their web page for it again and they have already updated it to show "Discontinued".

They never did have a picture of it there and I haven't seen one.
I was really only interested in one that is actually new.

I did email back to them with my VIN, asking if the M136839D 75 amp alternator they show is a reman, and to please check fitment of the discontinued 95 amp alt on my car, and, holy cow, reply just popped into my inbox and it says:
"I can't use non Mitsubishi VIN numbers but M136839D is still available and is a re-manufactured part. MD136839 is the original part number and is obsolete, when part numbers are displayed like this with M######D it indicates a reman."

Well holy cow.
 
I've had good experiences with denso remans.

There are 75 amp units still offered new by the aftermarket.
No feedback on those but they're all new alternators/components.
Rock auto offers them for 1g and 2gs

Other than that the only thing to check for ODD charging issues is the regulator plug for connection issues

And voltage drop test with a high load on the alternator the voltage drop between output lug on alternator and battery positive.
Then same high load high alternator amp output condition
The voltage drop from alternator case to battery negative.
Both should be low less than .2-.3 volts at high amp output.
If high check connections/wiring etc.
Those reading should also be close to one another.

Also an alternator is junk if it produces too much AC voltage under any condition.
Low load high load low or high RPM.
.3 volts AC is pushing it. Most say .5 but that is way too high IMHO.
Your solid state components will thank you for checking this....

That is a rectifier issue if it bleeds AC.
Also can be a tell for poor hi RPM output as well.
 
Yes, I've noticed the "NAPA New" 75 amp alternator part # NNE 1N8258 made by BBB. $130 from NAPA.
I do want to try "alternator in the stock position" one more time.
I have never had a heat shield between the alternator and exhaust parts. I would think that could make a big difference. So I'm going to make one up and get it on there before I put another alternator in.
The "regulator plug" I guess is the 2 conductor plug that plugs into the alternator, the one with terminals labeled "S" and "L" in the factory manual?
 
I get my reman ALTS from an alternator shop.
Never do anything with Crapzone.

Battery posts and connectors must be metal bright before tight connections.
Check grounds, make sure they're super tight, and add more grounds, like Chassis, frame, motor block - since DC current runs Negative to Positive.
More ground connections, the better the current flow from the battery.

If the battery has issues, get a new one. For a battery with issues will blow ALTS.

Normal voltage is 13.8-14.5VDC at idle

Good luck - DSM
 
I never do any Autozone anything either LOL.
Taking the old alt into an alternator shop is how I used to do it about 40 years ago.
I like that method, and if I knew more about the shops around here I would maybe try that again. For every good shop there are probably quite a few crappy ones.

With the Saturn relocated alternator setups, do they still use a 4 rib belt which also drives the water pump, like the stock setup does?
 
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