Alternator Joy then no Joy in Denver

[1911Guy]

This is kind of a follow up to a problem I was having with the alternator in my 1982SC.

Just a quick recap:

Part One.
Bouncing Tach, drained battery, posts and help from this website. New battery. Checked all fuses and grounds. No Alternator light when switched to no. Bulb tested ok. Decided it was the alternator.

Part Two.
Decided it was time to replace the alternator. Read and re-read the manuals - 101, Bentley, and the posts on this website. Thanks to all who responded, you know who you are.

Saturday, 7:00AM Disconnected the battery @ ground and started the process. All came apart just fine and there were no surprises. Pulled out the old (1992 dated) remanufactured unit and dropped in a new Bosch rebuild. The disassembly and assembly was clean and straight forward. Got it all put back together without incident. During all of this I had a trickle charger bringing my new battery to full power.

I cleaned up my tools and put everything away. Very nervous about turning the key, I just chilled and re-read all of the instructions and manuals just incase I missed something. So far so good.

I could not bring myself to turning the key on Saturday as I kept running the process over and over in my head. Could find nothing wrong.

Sunday AM. Got up early and said to myself it is now or never. Checked the battery- full load. Got in, turned the key to ON and was greeted with a bright ALT light. Good. Turned the key to START, Car starts, ALT light turns off, all is well.

Took the car out for a 25-30 mile drive on a beautiful Colorado morning. One stop to turn motor off. Back in, started, alt. light on then off as it should be. Came home feeling pretty good about what I had just accomplished.

Parked the car on the street, swept out and cleaned the garage. Upon returning to the car to put it in the garage, Got in - turned the key to ON -

GASP...... NO ALTERNATOR LIGHT!!!!!!!!!

W.T.F I thought to myself. Car started, I pulled it into the garage, covered the car up and became depressed the rest of the day.

So Pelican Gods, I beg for another Divine Intervention.
What happened here?

[kach22i]

Right after my alternator installation I went to the regular auto shop a block from my house and had them test the charging system. I was worried about the alternator ground and the voltage regulator status. For $35, I got a read out, everything was okay - took 30 minutes.

I thought I posted this before or around the same time you were doing your work.

Auto shops have better equipment than what you can pick up over the counter, why not take advantage of it?

Does your alternator have a built-in voltage regulator or external (like mine) voltage regulator?

You don't have points, right? What do you have?

Your ground strap either at the alternator/alternator housing or the stap at the transmission could of come lose. Start at square one, as in the 101 Projects book and recheck all your work. Look for the simple stuff first.

[1911Guy]

Does your alternator have a built-in voltage regulator or external (like mine) voltage regulator?

The V/R is built into the Alternator

You don't have points, right? What do you have?

1982 911SC 3.0

Your ground strap either at the alternator/alternator housing or the stap at the transmission could of come lose. Start at square one, as in the 101 Projects book and recheck all your work. Look for the simple stuff first.

Re checked ground straps at ALT and transmission, and battery. Read 101 about 101 times

I'm stumped here. I'll try again.

[Early_S_Man]

Probably just a coincidence ... #1816 bulbs [and those plastic bulb holders] don't last forever! Get another couple [so you will have a spare] and pull out the oil combination gauge and test the old bulb and holder. If your bulb holder doesn't already have the parallel bypass resistor mounted on it ... consider doing it yourself, per the following bulletin:

[1911Guy]

Early-S-Man,

Mine being a 1982 would have these upgrades already - no? Or are you just speaking of the bulb and socket in the insturment guage?

[Early_S_Man]

I was just referring to the resistor and bulb holder ...

[1911Guy]

Early_S_Man,

Thanks. Just wanted to be sure.

[LanceS4803]

Early S Man,
Thanks for the tech bulletin! Copied for reference file.
Is there a CD available with this type of information?
Lance

[1911Guy]

OK, The Alt. light is intermittant. It works as it should in the AM when the car is cool and does not work as it should in the PM.

What are the chances this is a rebuilt alt. issue vs. another issue?

[kach22i]

FYI: On the wall of the rebuild shop I went to for my alternator there was a FAQ bulletin baord. In it it explained how a bench test could show a false positive, and the resistors could still be bad. I don't remember much about the details.

[Early_S_Man]

The only type of fault I have ever encountered that would [and did -- way back when, multiple times] cause an intermittent alternator warning lamp ... is excessively worn brushes!

I suppose there could be other causes, such as a corroded & loose Faston connector on the Blue #61 wire.