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| Battery Light On While Driving (Page 1/4) |
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MERATIME
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MAR 20, 10:19 PM
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Hello all. I have a 1987 Pontiac Fiero 2.5 L 5sp manual transmission. The battery light stays illuminated on the information gauge when driving. I put in a new battery and I put in a new alternator last week, I checked the grounds and things seem to be fine visually under the hood. What else could be causing this light to stay on the dash ? Any help would be appreciated. Thank you. [This message has been edited by MERATIME (edited 03-20-2025).]
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cartercarbaficionado
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MAR 21, 06:37 AM
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| quote | Originally posted by MERATIME:
Hello all. I have a 1987 Pontiac Fiero 2.5 L 5sp manual transmission. The battery light stays illuminated on the information gauge when driving. I put in a new battery and I put in a new alternator last week, I checked the grounds and things seem to be fine visually under the hood. What else could be causing this light to stay on the dash ? Any help would be appreciated. Thank you.
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its not charging or giving voltage to the circuit that tells the light its fine. i don't remember how the 87 is wired off the top of my head but I think the circuit is using one of the 2 tabs on the side of the alternator
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Vintage-Nut
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MAR 21, 07:23 AM
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First, check the belt tension of the Generator/Alternator
Second, you'll need a voltmeter to measure the battery {12.5 DC Volts or Better}
*It is important to start with a fully charged battery as the Generator/Alternator will not even try to charge an undercharged battery...
If the battery won't hold 12.5V after charging - replace it
With a fully charged battery...
Use a voltmeter to measure the battery at idle AND 3k RPM - 13.5 volts to 14.5 volts
*If the Generator/Alternator won't charge the battery at 13.5 volts to 14.5 volts...then
Check the Generator/Alternator Connections
With the KEY at RUN position {Engine NOT Running}
Check All Cable/Wires Have 12V
*If NO, check the fuses/wires/cable
*If ALL have 12V - replace the Generator/Alternator------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles
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MERATIME
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MAR 21, 11:28 AM
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Thank you all for the replies. so after reading the responses, the new battery or the new alternator which I just recently purchased and installed is not good. I’ll go ahead and go to an AutoZone or O’Reilly and I’ll run test with the battery and get a second opinion as the volt test is being done.
Note: The alternator I have on my vehicle has the four tab connector. Could any of those four outputs be the problem? Thanks.[This message has been edited by MERATIME (edited 03-21-2025).]
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Dennis LaGrua
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MAR 21, 11:52 AM
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Easy way to check. Buy a cheap voltohm meter. They are quite inexpensive on ebay. Use this meter to measure the voltage across the battery terminals. On a cold start you should read about 14.3 volts +/- 0.5v or in that area. if you don't read that .you will need to check out the charging circuit. If the car is not started the battery voltage on a good battery should be about 12.7 Volts. ------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "
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Vintage-Nut
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MAR 21, 02:00 PM
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| quote | | the new battery or the new alternator which I just recently purchase |
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Did you buy a brand-new alternator OR Remanufactured?
| quote | | The alternator I have on my vehicle has the four tab connector. |
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The alternator has one big red cable to the battery stud/nut and a plug with three wires
| quote | | Could any of those four outputs be the problem? |
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Perhaps the regulator in the alternator has a defect OR the car circuits which as I already listed to test.
BEFORE going an auto store to test the alternator, charge the battery so it is fully charged....
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MERATIME
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MAR 24, 03:23 PM
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Thank you all for the additional information and advice. Voltmeter on my list.
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MERATIME
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MAR 28, 03:11 AM
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UPDATE : hello folks, I ran a test with a voltmeter and sure enough. It’s the alternator that was bad and this is the reading that was shown:
The battery was under charged at 11.2V so it’s now fully charged at 12.3 V. The good news is that my alternator was under warranty and it will be exchanged. Also additional good news the place where I bought the alternator they’re offering to exchange it for one that’s much more compatible for the Fiero. Anyone have any alternator suggestionsfor at 87SE with an iron Duke manual? Thank you all for your assistance.
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cartercarbaficionado
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MAR 28, 03:24 AM
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| quote | Originally posted by MERATIME:
UPDATE : hello folks, I ran a test with a voltmeter and sure enough. It’s the alternator that was bad and this is the reading that was shown:
The battery was under charged at 11.2V so it’s now fully charged at 12.3 V. The good news is that my alternator was under warranty and it will be exchanged. Also additional good news the place where I bought the alternator they’re offering to exchange it for one that’s much more compatible for the Fiero. Anyone have any alternator suggestionsfor at 87SE with an iron Duke manual? Thank you all for your assistance. |
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most people are saying to use the 88 one. honestly I think that or stock 87 stuff is fine.
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Mike in Sydney
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MAR 28, 04:51 AM
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| quote | Originally posted by cartercarbaficionado:
most people are saying to use the 88 one. honestly I think that or stock 87 stuff is fine.
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Depends on your electrical loads. If you plan to install a powerful amplifier, additional lights, and have A/C, etc. then consider the CS130 alternator. You will need to use a different plug but instructions can be found in the archives. It’s not a difficult swap. If you aren’t planning on any electrical or sound system upgrades and you don’t have A/C, a standard replacement will suffice. Rock Auto or Summit Racing is a good place to start looking.[This message has been edited by Mike in Sydney (edited 03-28-2025).]
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