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).]
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.
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
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
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).]
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 "
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.
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.
most people are saying to use the 88 one. honestly I think that or stock 87 stuff is fine.
most people are saying to use the 88 one. honestly I think that or stock 87 stuff is fine.
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).]
I really appreciate the advice & time. Yes, the alternator was new , not rebuilt. This Fiero does not have a compressor and is a bone stock / no power anything SE that will not have any added electrical-required aftermarket stuff. I checked the C500 lines and checked the fuses and they are good. I plan to make sure the battery has full charge when replacing the alternator. I will look into RA & SU for their selection. Thanks all!
You're adding confusing info to this thread, as the OP has a 2.5 and not a 2.8 engine.
every 88 2.5 ive ever seen isnt using the 85 and prior alternator im used to patrick. if there isnt supposed to be a different alternator thats news to me.
every 88 2.5 ive ever seen isnt using the 85 and prior alternator im used to patrick. if there isnt supposed to be a different alternator thats news to me.
Here's some news for you then... the '87 and '88 2.5 alternators are the same CS models.
It's the 2.8 engines where only the 88's have the CS alternator instead of the older style SI alternators.
Again, it’s great to hear all this professional advice from you guys. Here’s the update. I spent this morning at O’Reilly’s and they assisted me looking for a specific type of alternator for this Fiero. This Fiero has had modifications on it before I owned. There is a regular Belt pulley that’s required not the serpentine. There’s a 12 o’clock and 6 o’clock positioned bolt for the mounting & adjusting and there’s a pigtail style connector plug. I’m only finding Alternators that have two out of three of the features. Do you guys know if there is an alternator that is complete with these specifics in the photos? On the previous alternator, I had switched out the pulley and I hope that is not the reason getting the battery/charging light on the dash. Thanks again for all your help.
[This message has been edited by MERATIME (edited 03-29-2025).]
Again, it’s great to hear all this professional advice from you guys. Here’s the update. I spent this morning at O’Reilly’s and they assisted me looking for a specific type of alternator for this Fiero. This Fiero has had modifications on it before I owned. There is a regular Belt pulley that’s required not the serpentine. There’s a 12 o’clock and 6 o’clock positioned bolt for the mounting & adjusting and there’s a pigtail style connector plug. I’m only finding Alternators that have two out of three of the features. Do you guys know if there is an alternator that is complete with these specifics in the photos? On the previous alternator, I had switched out the pulley and I hope that is not the reason getting the battery/charging light on the dash. Thanks again for all your help.
This Fiero has had modifications on it before I owned. There is a regular Belt pulley that’s required not the serpentine. There’s a 12 o’clock and 6 o’clock positioned bolt for the mounting & adjusting...
I'll say it's been modified! This is what you're supposed to have...
How about taking a photo of this "modification" and posting it here. I'm curious how the belting has been arranged, as well as how the totally different clocking for the mounting ears has been utilized.
[This message has been edited by Patrick (edited 03-29-2025).]
Hello Patrick, here are photos of the alternator & belt set up that I currently have on this 87 SE. It’s nighttime here now so I took these just so you have something to see the following day. Photos of the water pump set up, the lower crank pulley and of the defective alternator.
There is no compressor installed. In the next photo,You will see the bundle of wires on the bottom rightwhich go to the compressor.
Photos of the current set up below:
[This message has been edited by MERATIME (edited 03-29-2025).]
...here are photos of the alternator & belt set up that I currently have on this 87 SE.
That's bizarre! If I'm seeing things correctly, the image above is of where the '87 duke's factory serpentine belt tensioner pulley is supposed to be. It's missing, and apparently someone has sort of retrofitted the '84-'86 duke's inferior V-belt system to this '87. The only reason I can see someone doing that is if they were having a problem finding/replacing the 87's belt tensioner after it failed... but damn!
This is what your '87 duke belt system (with A/C) is supposed to look like.
quote
Originally posted by MERATIME:
...the place where I bought the alternator they’re offering to exchange it for one that’s much more compatible for the Fiero.
Since you have a non-factory setup, you better just get a direct replacement for your current alternator... but make sure it is the alternator that's fubared and not the wiring. Who knows what else has been messed with on that Fiero!
[This message has been edited by Patrick (edited 03-30-2025).]
huh. thats suuuper weird. unfortunately i dont have any spare late duke stuff atm to send your way. you can find it lster if you wanna make it easier but it seems your wiring has been fussed with or someone has take the split loom off before looking for something
I would like very much to get this Duke back to factory specs, but I currently don’t have a budget for it. Plus, I have been checking frequently junk, parts for 87-88 SE’s in junkyards or on FB, OfferUp, but so far no luck. Please let me know if you all find any parts related or additional ideas or suggestions. Thanks again friends!
