I have a 1986 3.4l pr and I replaced my alternator (cs conversion) about two months ago with an AC DELCO reman. Everything was working fine, but about a month in, my volt gauge wouldn't show voltage (but would slightly move when ignition is on) and the volt light would be on. I got out the voltmeter and even under full electrical load it's charging 13.58 volts (14 with no load) when measured at the battery. I've reseated the alternator connector and verified the single wire with the bolt is nice and tight.
I took it to Advance Auto yesterday and they ran a test on it - they had the same values as far as voltage. However, it did come back with "excessive ripple" with the range being 210mV. Would that cause the volt light to come on and the gauge not show any voltage?
Please clarify; do you mean you see almost no deflection at all on your Fiero's voltmeter needle, and a separate Volt-Ohm test meter is showing 13-14 volts? If so, what is the engine-running voltage at any battery tap in the fuse block in the driver's footwell? Ripple: your alternator is producing 0.2 volts of AC on top of 13.5 to 14 volts DC.
Likely One or more Diodes in the Rectifier have problems.
Most ACdelco parts only have 30-90 day warranty. Go check and if possible return under warranty. If not... I use AZ parts w/ lifetime warranty that just need phone # to track in the system. IOW you won't need a receipt months to years later if have problem again.
alt should be above 14v, close to 15vdc.
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Originally posted by Rexgirl: Ripple: your alternator is producing 0.2 volts of AC on top of 13.5 to 14 volts DC.
close enough but may not quite right. 1 diode dead means 1 or 2 stator winding is "dead" and can cause a volt drops on alt's output and big noise problem.
SI CS and most other alt's are 3 phase AC generator w/ 3 phase "full wave" rectifier to output DC. SI and some others are infamous for shorted diodes... when so does get AC on the output term, way more then 0.2v, and quickly kills the battery and more. CS often fails w/ open diodes not shorted diodes and shouldn't see real AC when rectifier dies.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
I guess my overall question is - what is it that's making the volt light come on and my gauge to not register any voltage? Because with my tests at the battery and fusebox, and Advance Auto's check of the alternator, it's producing well above 12v.
If the oil pressure gauge is working as normal then the voltmeter should be as well since they are wired in parallel. Gall757 and Ogre are correct in suspecting an alternator issue.
Replaced the alternator under warranty. Not the problem.
Pulled the gauge pod and discovered the connectors simply were not making good contact. Whatever combination was giving signal to the oil pressure gauge, the backlights and the volt light, but somehow not pushing the volt gauge (despite some slight movement on startup).
I think in summary here - if I realized that the volt gauge should read the battery voltage when in accessory mode, I would have figured out the alternator wasn't the problem - especially when it was pushing out 14 volts.
Just an update for future generations - the ultimate problem was the pins that go into the circuit board of the gauge pod came loose from the circuit board. Re-soldered the connections and all good.
Just to add a bit of confusion... when the CS alternator died in my Formula recently (as reported Here), the volt light in the Rally Gauge Panel never did illuminate, although the gauge itself was showing lower and lower voltage as I was trying to drive the car home... until the engine died due to a basically dead battery.
Yes, the volt bulb was good (illuminates with key ON)... and no, I'm not referring to the charge warning light in the instrument cluster.
I'm not looking for any answers, I'm just adding to the knowledge base.
Originally posted by Patrick: Just to add a bit of confusion... when the CS alternator died in my Formula recently (as reported Here), the volt light in the Rally Gauge Panel never did illuminate, although the gauge itself was showing lower and lower voltage as I was trying to drive the car home... until the engine died due to a basically dead battery.
Yes, the volt bulb was good (illuminates with key ON)... and no, I'm not referring to the charge warning light in the instrument cluster.
I'm not looking for any answers, I'm just adding to the knowledge base.
The Volt Light is just a "feature" tied to the meter and can't trust either when you have or "just think" you have real problems. IOW same issue can't trust dash's OP, Temp, Tach, etc w/o double check w/ real tools or scan ECM.
Both see a local volt at a given point of all wiring that can and often does have crap wire(s) to +, ground or both. Volt gauge in other vehicle mostly do same.
Never have a Fiero Volt meter to take apart a see just how the light is wired but still does very little and should trust it or the meter. Think just get power from gauge fuse and ground at G201 and G202 same as most things in the cabin but don't have notes on laptop. That alone has problems not to trust them.
Unlike most old OE Amp meters had a shut in the engine bay to read amps to/from alt or battery. Side Note: You have many new cars using shuts that used by PCM to monitor battery level, charge rate, etc, and many times you must Reset/relearn the PCM when you replace the battery. If you fail to do that, new battery will have problems. Some are easy to see because "sometime" w/ small wires often on Neg battery term.
