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Discussion Starter · #1 ·
Ok, I've searched these great forums and ha e yet to find a solid answer so I'll post here. My 2001 GT just started having the battery and brake light come on yesterday. I had a brand new alternator for my GTS project car I swapped out. My old battery was reading 12.5 bolts at the battery before. After swapping the alternator, I'm up to 13.7 volts, but battery/brake light still intermittently comes on and my AC blower slows down when light comes on. All battery connections are good, I replaced my neg. terminal a while back, positive was slightly loose, but that was corrected. I've checked the ground strap on the firewall and ground on the back of the head head, all are good. Could a bad battery cause this? Battery does not seem weak at all on cold or warm start.
 

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Discussion Starter · #2 ·
Ok, so I took the car to OReilly and got them to test the battery and alternator. The scanner is showing the alternator is bad and the battery is good. The alternator is brand new and I purchased from. DC Electric through Amazon 2 years ago. It's been in a box since. I did notice the 4 wire plug into the alternator looks to be in rough shape. I soldiered a new one into my GTS harness a while back before I had to abandon that project so tomorrow, I'll cut that plug out and soldier into my 2001 GT and see if this fixes the problem. The battery/brake light only intermittently comes on with the new alternator so I'm not completely sure this alternator is bad.
 

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Discussion Starter · #3 ·
OK, so now I'm running out of ideas. The lights keep coming on after I had the factory alternator rebuilt. I replaced all my drive belts and pulleys, neg. battery cable, check every ground wire in the factory manual, replaced the pig tail to the alternator AND check the wire in the circuit for the lights shown in the factory manual between the alternator pig tail and the small plug on the side of the fuse block. My ground strap on the firewall is slightly frayed and my positive battery cable was slightly loose. I think I'm going to replace both of these and see what happens. Any one else have any issues like this? The lights only come on when I hit a bump so I'm almost positive it's a bad connection some where.
 

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It the battery securely fastened down? There's not much clearance between the battery terminals and the hood. Maybe your battery is getting airborne just enough to touch the backside of the hood and momentarily short out?
 

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2005 Spyder GT
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It the battery securely fastened down? There's not much clearance between the battery terminals and the hood. Maybe your battery is getting airborne just enough to touch the backside of the hood and momentarily short out?
I would think a couple bucks worth of plastic battery terminal caps would prevent that, no?
 

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Discussion Starter · #6 ·
It the battery securely fastened down? There's not much clearance between the battery terminals and the hood. Maybe your battery is getting airborne just enough to touch the backside of the hood and momentarily short out?
Oh yea, the battery tie down is tight. I'll post a video of it next time this happens. The car runs fine.....sort of. When thr AC is on, the blower motor changes is RPM thus, telling me it's got a voltage drop. I took the ground strap off today, cleaned the ends and reinstalled. I'll see if that helps. I'm running out of ideas here.
 

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Discussion Starter · #7 ·
I would think a couple bucks worth of plastic battery terminal caps would prevent that, no?
Yea, I have a plastic cover on the positive cable. I'll get one for the neg too. A friend that's a big classic car guy said to run another ground wire from the post to the back of the engine head or body. It maybe my factory ground isn't sufficient.
 

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Discussion Starter · #8 ·
Well I think what ever broke, was the problem with my charging issue and I think it's the harmonic balancer. Driving to work this morning, my 3G started making a loud whinning noise and I smells burning rubber/plastic. Got the car to my buddy's shop for him to inspect, but I do need a new lower timing cover. If anyone has an extra one they want to sell I'd be interested. The car runs fine other than these 2 issues but, I suspect the balancer is bad and was rubbing on the cracked up timing cover. Should know more later today.
 

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2005 Spyder GT
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With car running, use a multimeter to Check the alternator output AT THE ALTERNATOR under different loads to see how much it drops, then do the same AT THE BATTERY. Any differences in the readings should help narrow down where the problem lies (alternator, battery, wiring harnesses, grounds).
A second ground, as suggested, is a good idea to help pinpoint the problem.
 

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Discussion Starter · #11 ·
Found the problem. My rebuilt OEM alternator died. Is barely putting out 12 volts. I'm putting the aftermarket one bad on tomorrow until I can take the OEM one back to the shop that rebuilt it.im ordering a new lower timing cover now, so when that comes in, I'll put everything back together at one time.
 

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It certainly sucks when you buy and install a new or rebuilt part that turns out to be bad.
It sucks even more when you are driving across the country with all of your personal belongings in a box truck and have to replace a starter "TWICE" along the way due to shoddy rebuilt parts from some local yokle repair shop. That was 40 years ago and I would be hard pressed to count how many more times I've bought defective parts that were supposedly new or "professionally rebuilt."
 

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Discussion Starter · #13 ·
OK, I REINSTALLED the cheap Chinese alternator from DB Electrical, it works.....sort of. Under NO load I'm reading 12.4 bolts across the battery terminals. With the AC on, I get 13.8 volts. Looking at the numbers, this tells me this alternator is bad too from the ranges given in the FSM. Can anyone confirm this? What are yall getting at the battery under no load? With AC on? My battery/brake light still intermittently come on every now and then.
Gauge Measuring instrument Wood Clock Technology
 

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Discussion Starter · #14 ·
OK, so apparently I was not checking my alternator correctly. I've yet to see over 14 volts on any day with any of the 3 alternators I've had on this car. The batt/brake light still intermittently come on but, now I'm questioning the diodes in the instrument cluster. In vol. 16 of the FSM, the diagram shows 2 diodes in the cluster near the lights and in the beginning of the charging section, it mentions testing these diodes but, doesn't say how. Anyone experienced failed diodes I their instrument cluster, if so then what were thr symptoms?
 

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Discussion Starter · #15 ·
Welp, my charging issue is BACK! Its like the voltage regulator is not working. Voltage bounces around from 11.9 volts to 13.5 volts. I install a 2 gauge pillar pod today with one for volts and one for oil pressure (still have yet to connect this due to not having access through the firewall). I did pick up my OEM alternator from the rebuild shop and it was a blown diode in that failed after being rebuilt. Will try to swap this out later this week. I also added another ground wire along side the OEM ground coming off the battery hoping this would fix the issue but no. So far I have check all of the highlighted wires for continunity, all of which are good. If this rebuilt OEM alternator doesnt fix this, then I am moving on to the ECM (I really hope this isnt the issue considering there are NO Mitsubishi dealers within 1 hour drive from me.

Rectangle Slope Font Parallel Engineering
 

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Discussion Starter · #16 ·
OK, I checked the ground circuit for resistance and that checks out. Tomorrow morning I'm going to back probe the wires from the alternator pigtail to the ECM. I know the FSM gives the voltage to look for but, not sure what to do after that if it doesn't check out. Bad ECM?
 

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Discussion Starter · #17 ·
Hand Nail Wood Musical instrument accessory Thumb

OK, so I think this might be my issue. The G wire from the ECM back to the voltage regulator is pretty dry at the pigtail. Going to cut out the damaged section and soldier in a new wire. If this doesn't work, I'll will check the 2 wires going back to the ecu for continuity and put my rebuilt OEM alternator back on. If that doesn't fix it, then it has to be the ECU (I really hope this isn't the case).
 

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Unmount the fuse box and check for loose connections. Also check the pins on the harness pigtail connector and alternator. Spray some electrical contact cleaner on male pins and female connector.
 

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Discussion Starter · #19 ·
Unmount the fuse box and check for loose connections. Also check the pins on the harness pigtail connector and alternator. Spray some electrical contact cleaner on male pins and female connector.
Done. The pigtail is brand new as is the Chinese alternator. My wire repair was ineffective. Charging issue remains. Will unbolt the fuse block this weekend and also install new battery terminals, reinstall factory alternator and unbolt the negative cable on the battery at the midpoint lug and head and clean (not that they are loose or corroded). This is pissing me off the more time I spend on this car. I really just want to drive and enjoy this car but, it doesnt seem to want that.

I did trace the plug in underneath the fuse block to the connector in the interior fuse block so I am going to check those wires too albeit do not look like they have ever been disturbed. Its definately a charging issue as I have noticed with my A pillar pod volt meter. I see the factory alternators have been discontinued. I contemplated on going to Pull A Part and getting an OEM alternator just to see if maybe something failed in my OEM that was not replaced on the rebuild. The shop that rebuilt it replaced the rectifier, bearing and regulator I know. When it was bench tested it put out 14.5 volts this last time. If this rebuilt OEM alternator doesnt work, I might have to do this.
 

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Done. The pigtail is brand new as is the Chinese alternator. My wire repair was ineffective. Charging issue remains. Will unbolt the fuse block this weekend and also install new battery terminals, reinstall factory alternator and unbolt the negative cable on the battery at the midpoint lug and head and clean (not that they are loose or corroded). This is pissing me off the more time I spend on this car. I really just want to drive and enjoy this car but, it doesnt seem to want that.

I did trace the plug in underneath the fuse block to the connector in the interior fuse block so I am going to check those wires too albeit do not look like they have ever been disturbed. Its definately a charging issue as I have noticed with my A pillar pod volt meter. I see the factory alternators have been discontinued. I contemplated on going to Pull A Part and getting an OEM alternator just to see if maybe something failed in my OEM that was not replaced on the rebuild. The shop that rebuilt it replaced the rectifier, bearing and regulator I know. When it was bench tested it put out 14.5 volts this last time. If this rebuilt OEM alternator doesnt work, I might have to do this.
I assume you checked all associated fuses and relays, fusible link, etc?
I was looking at some fuse box diagrams and noticed there was a "generator relay", at least according to that diagram but dunno if its accurate or not. Change your alternator belt too if you haven't already, and make sure its adjusted properly.
 
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