Another alternator or voltage regulator question

[RDM]

Productive day, as I swapped out my non-starting starter for a reserve I bought off the board many years ago.

Symptoms were that the starter would click and voltage at the lighter would go to zero.. The fuel pump would buzz, but no starting. This went from intermittent to all the time in about two days. Once I removed the starter, I found that the solenoid worked fine, but the starter motor didn't turn.

Anyway, as part of this investigation I found that my voltage at the battery never got above about 13.2 volts. I subsequently traded the solid state voltage regulator on the car for one of the original mechanical ones, and got to 13.6, then 13.9 for yet another mechanical VR.

The battery is an Optima yellow top and has never given trouble.

So do I have an alternator problem? It seems unlikely I'd have three bad voltage regulators....

[mysocal911]

Originally Posted by RDM

Productive day, as I swapped out my non-starting starter for a reserve I bought off the board many years ago.

Symptoms were that the starter would click and voltage at the lighter would go to zero.. The fuel pump would buzz, but no starting. This went from intermittent to all the time in about two days. Once I removed the starter, I found that the solenoid worked fine, but the starter motor didn't turn.

Anyway, as part of this investigation I found that my voltage at the battery never got above about 13.2 volts. I subsequently traded the solid state voltage regulator on the car for one of the original mechanical ones, and got to 13.6, then 13.9 for yet another mechanical VR.

The battery is an Optima yellow top and has never given trouble.

So do I have an alternator problem? It seems unlikely I'd have three bad voltage regulators....

You can easily adjust the spring tension of the regulator's points for basically any battery voltage you want.
Force the points closed and rev the engine for max alternator output voltage test.

[RDM]

Originally Posted by mysocal911

Force the points closed and rev the engine for max alternator output voltage test.

How high could that voltage go?

What might be fried in the process?

[mysocal911]

Originally Posted by RDM

How high could that voltage go?

What might be fried in the process?

It depends on the battery. For a small battery, it could easily go to 18 - 20*volts.
A large battery like for a 911 3.2, 14 -15 volts. Obviously, it's based on the alternator's
rating.

[kltarga72]

Alternators producing 13.5 vdc or below is failing.
A car alternator should typically put out 13.8 to 14.5 volts when the engine is running and charging. Readings within this range indicate that the alternator is effectively charging the battery and powering the vehicle's electrical systems.
Your alternator may be on its last road trip.

[mysocal911]

Originally Posted by kltarga72

Alternators producing 13.5 vdc or below is failing.
A car alternator should typically put out 13.8 to 14.5 volts when the engine is running and charging. Readings within this range indicate that the alternator is effectively charging the battery and powering the vehicle's electrical systems.
Your alternator may be on its last road trip.

Not really! Did you forget about voltage drops from the rear to the front?
How about a bad battery limiting the voltage output of the alternator?

It's not always that simple.

[RDM]

If it's not 13.8 to 14.4 at the battery, then it's not doing its job. I think it probably is that simple.

I have it out now. And have also removed the little insulated critter house built back over cylinder number 6. No critters, thankfully.

Next two questions:

1. The top air deflector fin is cracked- is there a reliable way to repair these?

2. My fan, housing, and strap all look lousy. Anyone have success beautifying at home, or is this a job for a pro?

[mysocal911]

Originally Posted by RDM

If it's not 13.8 to 14.4 at the battery, then it's not doing its job. I think it probably is that simple.

I have it out now. And have also removed the little insulated critter house built back over cylinder number 6. No critters, thankfully.

Next two questions:

1. The top air deflector fin is cracked- is there a reliable way to repair these?

2. My fan, housing, and strap all look lousy. Anyone have success beautifying at home, or is this a job for a pro?

Then just buy another alternator from Pelican Parts. If you get the same results, just say "It would've needed one eventually.".
Then you'll have to troubleshoot and think!

[kyngfish]

Getting an alternator rebuilt or getting a new one usually isn’t too pricey as far as p cars go. If it has any kind of mileage on it I would just do it to remove it from the equation. Ask me how I know

[RDM]

I plan on taking the alternator and the starter to my local automotive electrical shop to see what they can do and at what cost.

[kltarga72]

I had to replace my alternator recently (1980 SC), tried to have it rebuilt but repair shop said no way. I purchased the alternator from PP that has the internal voltage regulator, more than 500 miles on it and is working well.
heres the p/n 911-603-120-04-M262

[mysocal911]

Originally Posted by kltarga72

I had to replace my alternator recently (1980 SC), tried to have it rebuilt but repair shop said no way. I purchased the alternator from PP that has the internal voltage regulator, more than 500 miles on it and is working well.
heres the p/n 911-603-120-04-M262

It was the best Porsche alternator (Marchal 70A '76-'81) with an external regulator (reduced heat damage).
For some rebuilders, a simple and very reliable rebuild, if done right.

[GH85Carrera]

I had my original Valeo alternator rebuilt 29 years ago. It lasted 28 years, well over 100,000 miles and from 118 degree outside temps to 0 degree temps. Last year it started grumbling. The bearings were going out. I tried to get it rebuilt, and the guy found good bearings, but missed something as it would not charge. He went out of business a few days later. I just bought a new Valeo, and it works great. The old alternator was just barley charging when it was really hot outside, and after a full day of driving, so it was tired.