Bad Alternator? Don't be so quick to replace it.

[Fierofool]

When my Brother's alternator failed on his 86GT, I promptly called the auto parts to order a replacement.  The young woman who answered the phone and took the order told me that there was a Technical Data Bulletin on all Fieros regarding the alternator charging circuit.

She warned that she didn't want to sell me an alternator because once installed, she couldn't take it back.  She said that the technical bulletin advised that on all Fieros, the charging circuit runs through the battery light bulb on the instrument panel.  On all cars with the auxilliary voltage/oil gauge pod atop the front center console, it's inside the voltage meter just above the battery symbol.  When the ignition is turned to the "ON" position without starting the car, the bulb should light up showing "VOLTS". 

On all others without the auxilliary gauge pod, it's in the speedometer/tachometer pod.  When the ignition is turned to the "ON" position without starting the car, the bulb should light up showing "BAT" and a battery symbol.

If you have power in your battery and these indicators do not light up, try replacing the bulb first before replacing the alternator.  It could save you some bucks, and in the case of an automatic V6, a whole heap of time.  If the bulb is blown, it will not charge.  Even with a good alternator.

[TopNotch]

It is my understanding that 88 cars with the CS alternator do not have this problem.

[cogcaviz24]

wow!! that's pretty nuts

[Fierofool]

It is my understanding that 88 cars with the CS alternator do not have this problem.

I don't know.  Maybe someone else can verify that.  The young lady just said that the bulletin applied to all Fieros.  Is the CS alternator adaptable to the earlier models, or is the whole wiring schematic different for the 88 charging circuit?

[TopNotch]

The CS can be used on earlier cars, with an adapter plug, but it still involves the light bulb circuit.
I saw somewhere (Pennocks?) that you can jump the light bulb with a resistor, so that the alternator still works if it burns out. I can't remember the value, but 600 ohms sticks in my mind.
I think either the Ogre's cave or Oliver's pages has something about how to upgrade your alternator to the CS type, which is both smaller (so easier to change on an auto transmission car) and more efficient. There are links to the Ogre's cave and Oliver's pages on our site.

[cogcaviz24]

i had this exact issue on my car. the previous owner replaced the altenator, but a battery tester showed the altenator current bad. i read this thread and checked the bulb. it was good but one of the leads was bent so it couldn't make a connection

[pgackerman]

What do you mean one of the leads was bent so it couldn't make  connection?  Is this lead by the Volt light?  I charged my battery and my car starts, but the volt light is still on. I'm thinking the alternator needs replacement.

[Fierofool]

The lead he's referring to is probably the little wire leads on the bulb itself.  If the light stays on, then the alternator isn't charging.  With the car running, if you put your ohmmeter leads onto the battery posts, it should give you at least 14 V if it's putting out, otherwise it will probably be 12 or less and will continue to drop as the car runs.  I'm surprised you drove from Augusta to Savannah and back without problems.  It must be charging but at a lower voltage. 

[pgackerman]

Took the van to Jekyll.

Put the battery back in the Fiero today and it started right up.  Of course the battery light stayed on.  I'm planning on taking the alternator out tomorrow after work. I've read it has to come out from the bottom and I've read it can come out the top.  Do you have any guidance? 

[TopNotch]

It's easier if you have a manual transmission. There's a discussion of alternator removal on this page.

[Fierofool]

I've always taken mine out from the bottom.  I just removed one last month at the Pull-A-Part yard and I also dropped it out the bottom.  I find it easier to reach the bolts and definitely easy to maneuver it around the drive axle as opposed to the cooling tubes, manifold, valve cover, cruise cable and cruise vacuum lines.  Some manuals recommend removing the mounting bracket, but there's no need for that, either.  Not on a manual transmission car.

I have to totally disagree with the procedure described by The Fiero Factory, and I'm really surprised that those instructions came from them.  The alternator comes out the bottom of a pre-88 manual V6 very easily.  The Automatic is the one that requires removing the right wheel and fenderwell liner and other goodies.