Fellas,
I have an alternator question?——-Based on my new problem!
I (thought) I had to replaced my ‘85 SE 5-speed alternator; and I also purchased a new battery. Why? Because my dash mounted volt gauge-needle was always pointing in the red zone! My Fiero was dead, if wouldn’t start! Click—Click—Click—-Click—Click....
So we found a new 78 amp alternator to replace my “dead” 93 amp alternator {we could not find a new 93 amp one😟}.
Here is the problem: The dash volt-gauge showed that I am now all charged up. Except, there are moments (a few miles down the road) when the volt-gauge will sweep back into to the red zone again🤔. Why? What am I missing? My buddy is a licensed mechanic. He methodically checked all the fuses and connections on the alternator. My Fiero starts and goes OK. However, what would cause the intermittent lack of a full charge being shown? The charge will NOT show it to be consistent? The needle will ultimately point back to the red zone?
What am I missing? Please give me your thoughts.
Cordially,
Kevin

Ps. All battery connection are tight! The re-checking of my 93 amp alternator showed that this alternator was always good.

quote Originally posted by kevin: Fellas, I have an alternator question?——-Based on my new problem! I (thought) I had to replaced my ‘85 SE 5-speed alternator; and I also purchased a new battery. Why? Because my dash mounted volt gauge-needle was always pointing in the red zone! My Fiero was dead, if wouldn’t start! Click—Click—Click—-Click—Click.... So we found a new 78 amp alternator to replace my “dead” 93 amp alternator {we could not find a new 93 amp one😟}. Here is the problem: The dash volt-gauge showed that I am now all charged up. Except, there are moments (a few miles down the road) when the volt-gauge will sweep back into to the red zone again🤔. Why? What am I missing? My buddy is a licensed mechanic. He methodically checked all the fuses and connections on the alternator. My Fiero starts and goes OK. However, what would cause the intermittent lack of a full charge being shown? The charge will NOT show it to be consistent? The needle will ultimately point back to the red zone? What am I missing? Please give me your thoughts. Cordially, Kevin Ps. All battery connection are tight! The re-checking of my 93 amp alternator showed that this alternator was always good.

Sounds like an intermittent wiring problem. I had the same problem with another vehicle. Turns out the wiring was close enough to the steering mechanism that it had been wearing through the insulation and intermittently shorting out a 12-volt cable. I also had a 280 Z with an intermittent issue that was producing the same effect, but in this case, it was a bad factory crimping job that was doing it. They had used a copper sleeve to joint two ground wires to one larger one, but it had never been crimped. It was good for about 15 years and then started giving me issues. The weird thing was that with this "high resistance" connection, I could measure the correct voltage until I put a load on the system, like turning on the air conditioning, and then my voltmeter would register a low voltage.

"Smaller" alt = less power, even lower then advertise amps because that is Peak Amps.
You likely have AC because 93 amp alt so can have other problems w/ AC on.
See my Cave, Watt Story

Volts Going High then first thing connect real meter and drive if needed w/ that. Use extra wire(s) to read volts at battery w/ meter in the cabin. Make sure extra wires can't short or battery will dump > 100 Amps causing a fire.
Do Not trust a Dash Meter/gauges when have problems.

Check ECM "codes" too. If too high for > 2 sec can set DTC 53

If both alt's get same problem is likely wiring problem.
Like Iffy Side Plug can easily cause this.
Because Side plug is how regulator read alt output.
See my Cave, Alternator Sense

Alt ground is the alt case and mounting parts. Sometimes Iffy ground(s) can freak out the alt regulator too.

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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)

The Ogre's Fiero Cave