Wonky Alternator
Printed From: West Coast Fieros
Category: Technical Topics Forum
Forum Name: Technical Questions and Discussions
Forum Description: Got a technical question about your fiero? ask it here.
URL: http://www.westcoastfieros.com/forum/forum_posts.asp?TID=2063
Printed Date: 24 April 2025 at 6:39pm
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Topic: Wonky Alternator
Posted By: Romeo
Subject: Wonky Alternator
Date Posted: 05 September 2010 at 9:10pm
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Well, she couldn't kill me, so Gretchin did the next best thing: She broke. lol Current condition is that the Voltage Gauge is reaching into the red, where it then bounces off of the regulator (Which can be heard from the alternator itself). Alternator is putting out too much power to try and overcome through lights, heater fan and stereo (Simply slows the bouncing effect). I know it may seem crazy, but I believe it may actually be the battery. I noticed when the alternator would disengage, the lights would dim. As it got worse, the engine would actually follow the bouncing too (Power would fall off when the alternator disengaged) and she seems to be having trouble turninig over. Just my own observations, however. Hopefully I'm wrong, otherwise this will be the... Fourth battery I'll have had to replace in just over two years. ------------- Never shift into reverse without a back-up plan. |
Replies:
Posted By: Romeo
Date Posted: 06 September 2010 at 10:49am
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No one? No ideas? ------------- Never shift into reverse without a back-up plan. |
Posted By: Dawg
Date Posted: 06 September 2010 at 3:34pm
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The charging voltage should NEVER go over 14.4 volts for a liquid electrolyte lead-acid battery. Regardless of the load on the alternator. That regulator is going to cook your battery. Doesn't take long either. It does sound like there is something drawing tons of current. This is likely the root cause of the regulator dieing. The whole case overheats and takes the diodes and/or the regulator with it. I have a DC clamp meter here if you want to come over. I can measure very high loads without having to disconnect any wires. The Dawg ------------- You dream it up....I'll make it |
Posted By: Patrick
Date Posted: 06 September 2010 at 3:36pm
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Put the factory heat shield on that puppy.
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Romeo wrote:Posted By: Capt Fiero
Date Posted: 06 September 2010 at 6:48pm
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One thing I did not check at the track was that your battery cables were tight. A loose or damaged battery cable can create a resistance point tricking the alternator into charging wide open. Also double check all your grounds. Make sure you have a good battery to chassis, battery to block and block to chassis ground. I know the battery to chassis is a bit redundant, but I like to have it there. Also as an extra point to help, I run an 8 gauge wire direct from the alternator charge stud to the power distribution block that is on the fender just below the main wiring harness connector. (main power distribution just rearward of the battery) Again its redundant if the rest of your wiring is correct, but I am all about the fail safe when it comes to electrical. You can never have too many grounds and I like to have alternatives if a main system starts to fail. ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Romeo
Date Posted: 06 September 2010 at 7:54pm
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Damien, I just got into the country, does tomorrow work for you? And alright Patty, you win. I'll put the glorified pop can back on. lol ------------- Never shift into reverse without a back-up plan. |
Posted By: Dawg
Date Posted: 06 September 2010 at 8:05pm
PM'd
------------- You dream it up....I'll make it |
Posted By: Romeo
Date Posted: 07 November 2010 at 12:23pm
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Well, rebuild kit number number two (And as a result, battery number two) and the alternator is still full-fielding 24/7. I made sure the voltage regulator was hooked up properly in there, and everything was torqued nice. I have the glorified pop can attatched (Heat shield). Everything was done perfectly, and still this stupid thing isn't working still. Before I invest in a brand new alternator, anyone have any last ideas about why the stupid thing could still be going nuts? ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 07 November 2010 at 12:55pm
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I'm not at home so I can't send you a link, but there are some excellent websites describing how to check all components in an alternator. Heck, if you do a search here (or was it Pennock's?), I might've mentioned them in my thread describing my own alternator repair a year or so ago. You need to be checking/replacing the brushes, diode-trio, rectifier, regulator, stator, field... I think that's it.
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Posted By: Romeo
Date Posted: 07 November 2010 at 2:52pm
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You replaced the stator? And what do you mean check the field? As for everything else, I replaced all that and the bearing... ------------- Never shift into reverse without a back-up plan. |
Posted By: Capt Fiero
Date Posted: 07 November 2010 at 9:53pm
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I am wondering if you have a dead short in the windings or something. At this point, I would just say screw it, break down and buy a new one with a really good warranty. Just make sure and buy the one for A/C as it is rated at about 1.5 X the output. Bosch makes a good one, I put a Bosch one in Shirley's Fiero over 5 years ago and she drives it in rushour traffic 5 days a week and no problems from it at all. Works perfect. ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Dawg
Date Posted: 07 November 2010 at 11:08pm
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Take your friend Damien's offer and go to his place where he can determine if the load is indeed external or internal to the alternator. I doubt there is an internal short but it is possible. Were you not having this very problem before and this is why you purchased this used alternator in the first place??? If so, what are the odds that two alternators have the same internal short? The Dawg ------------- You dream it up....I'll make it |
Posted By: Patrick
Date Posted: 08 November 2010 at 1:07am
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Sorry, I got mixed up with a couple of the terms as I wasn't home when I last posted and was a little rushed. The items I was suggesting you check and replace as necessary were the brushes, diode trio, rectifier, regulator, stator, and rotor. Yes, I replaced the stator as it was toast.
There are plenty of good websites with helpful information on alternators. Have a look http://jeep.zerok.ru/index.php?page=39 - Here , and http://www.tpub.com/content/construction/14273/css/14273_51.htm - Here , and http://www.aa1car.com/library/charging_checks.htm - Here at sites that I used.
If I remember correctly, it was a brand new looking Bosch alternator that Tristan picked up at Pick-a-Part.
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Posted By: Dawg
Date Posted: 08 November 2010 at 7:45am
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Patrick, just to clarify, the diode trio IS the rectifier. In your write up above every time you mention "rectifier", I think you meant to say regulator. The Dawg ------------- You dream it up....I'll make it |
Posted By: Romeo
Date Posted: 08 November 2010 at 8:16am
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Only one alternator. I replaced my first alternator because I wanted a higher output alternator as a pre-emptive move for the sound system, however, everything seemed to go downhill a few months back (On the way to autocross, as it were). It should also be noted that every now and then, it will work normally for a little while, but after a sufficient jolt (Hard 1-2 shift, for example) it will go back to being screwy. I think I may just do a mix of what David and Patty said, I'll head to Edmunds Alternator and either get them to fix this one, or simply pick-up another from them. ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 08 November 2010 at 11:05am
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No no no, what I said IS what I meant. Damien, the diode trio and the rectifier (bridge) are separate entities. Have a look at the diagrams from http://jeep.zerok.ru/index.php?page=39 - Here .  Exploded View of Model 12SI Alternator
Exploded View of Model 17SI Alternator
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Posted By: Romeo
Date Posted: 08 November 2010 at 11:58am
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Oh well. In either case I'll make this Edmund's Alternators' problem to deal with. ------------- Never shift into reverse without a back-up plan. |
Posted By: kharmata
Date Posted: 08 November 2010 at 12:39pm
Charging basics. just in case. 
http://www.bcae1.com/charging.htm Oh and a good warning. Warning! Some people tell you that you can check your alternator by disconnecting it from the battery to see if the alternator can produce enough current to keep the engine running. BAD IDEA! Disconnecting the battery will subject the voltage regulator to significant voltage spikes which may cause an otherwise good alternator to fail. Even if there were no damaging spikes, this test would not indicate whether or not the alternator was good because the engine will easily run with a weak or failing alternator. |
Posted By: Romeo
Date Posted: 08 November 2010 at 1:15pm
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Yep yep. I know just how well the alternator is working - it cooked an 8-month old battery in no time flat. ------------- Never shift into reverse without a back-up plan. |
Posted By: Romeo
Date Posted: 10 November 2010 at 2:53pm
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Alright, so before I order in another alternator from Edmunds (I already have mine out) is there anything else that could cause the alternator to full-field all the time? Especially something that the in-car voltage monitor could pick up? ------------- Never shift into reverse without a back-up plan. |
Posted By: Romeo
Date Posted: 10 November 2010 at 3:06pm
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Actually, a more specific question: Could it be the actual connection to the regulater (The wires) that's causing the failure? ------------- Never shift into reverse without a back-up plan. |
Posted By: CFoss
Date Posted: 10 November 2010 at 6:59pm
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Absolutely it could be that. When I had lost the feed to the reg on my car, it would run ok due to self excitation from the altenator residual flux, but when I loaded it (Like turning on the headlights), the engine would skip a beat and the voltage of the whole car would go down. No reg = no field current = low voltage under load. Chay ------------- 86 SE 3.4 |
Posted By: Romeo
Date Posted: 10 November 2010 at 8:21pm
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Could it promote the opposite effect? If the wiring was wonky (ALLITERATION! YES!) could that cause the alternator to always try and pump out max voltage? ------------- Never shift into reverse without a back-up plan. |
Posted By: CFoss
Date Posted: 15 November 2010 at 10:03am
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That's more a sign of a busted voltage regulator (Stuck on boost).
An altenator requires higher field current for the voltage to go higher. This could only happen with good connections, and a reg stuck on boost, maxing out the field current.
Your voltage should not exceed 14.2 or so. Higher and your bat will cook.
Chay ------------- 86 SE 3.4 |
Posted By: Romeo
Date Posted: 15 November 2010 at 11:40am
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Well, I took a reading of the new alternator and it's at 14.7V Maybe the battery will take that? ------------- Never shift into reverse without a back-up plan. |
Posted By: kharmata
Date Posted: 15 November 2010 at 12:47pm
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Did you measure open circuit...? |
Posted By: Dawg
Date Posted: 15 November 2010 at 4:09pm
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Of course meaning no load on the alternator. It's possible that this alternator isn't charging at all or very little. That might cause it to have a higher than normal voltage for sure. Good idea Kev. The only way to know this is to measure the actual charging current. If it's pumping 14.7 volts 30 amps+ into a regular starting battery there won't be much battery left for long. The Dawg
------------- You dream it up....I'll make it |
Posted By: kharmata
Date Posted: 15 November 2010 at 4:15pm
If you measure it when you first start the car (battery connected) - and perhaps the battery is not fully charged - the voltage will be higher for a short time and as the battery builds up bit more of a voltage drop the volts will drop. If the battery is fully charged and you have this high...hmmm not sure. seems high. |
Posted By: Romeo
Date Posted: 15 November 2010 at 9:07pm
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Was flipping through my old notes about alternators though, and it doesn't seem that unrealistic. As far as I can see, an alternator tries to keep the battery at 14.5-14.7V. ------------- Never shift into reverse without a back-up plan. |
Posted By: CFoss
Date Posted: 15 November 2010 at 9:43pm
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To me, that's too high a voltage. Over the long term, my opinion is that it will cook. Start the car and idle. Measure the voltage. Rev up the car slowly to 2500rpm or so. Does the voltage level off, or keep climbing incrementally over the next minute or so? What does it top out at? My experience is that the voltage works like this: 1) Before starting, lowest voltage at the battery 2) Start. Idle. voltage is sub 14.2. voltage increases as car is reved indicating increased ability to send current to the battery as the engine speed increases 3) Voltage tops out quickly (On a decent battery) at a max of 14.2 or so. Voltage should not creep. There should be a hard limit on the upper voltage I found this after looking for a bit. Maybe 14.4 before it gasses... I've never seen one top out that high though. Voltages for common usagesThese are general voltage ranges for six-cell lead-acid batteries:
------------- 86 SE 3.4 |