Alternator not charging on Carrera 3.2 but no idiot light either...

[Tippy]

I blasted and painted my fan and housing a few months ago. After the paint job, I didn't realize my alternator wasn't charging until recently. I haven't driven the car much at all because I was trying to fix my leaning out issue.........a whole 'nuther thread about a "cliff" and a "Carrera".

Anyways, here's is what is going on (battery at 12.80v's):

1. Key on, no idiot light for the alternator illuminating when engine off
2. Pulled idiot light socket and found a bunch of corrosion on the spring contact - cleaned but still will not light with key on, not running
3. Took scotch-brite to bulb contact and still no light when key on, not running
4. Hooked a 9-volt up to idiot light bulb and it works fine
5. Checked voltage at idiot light socket and found NEGATIVE voltage with (+) from multimeter on the spring contact and the (-) on the sleeve (I'm assuming this is standard for all light sockets?).

I assume I have a wire crossed on the alternator???

[86 911 Targa]

Originally Posted by Tippy

I blasted and painted my fan and housing a few months ago. After the paint job, I didn't realize my alternator wasn't charging until recently. I haven't driven the car much at all because I was trying to fix my leaning out issue.........a whole 'nuther thread about a "cliff" and a "Carrera".

Anyways, here's is what is going on (battery at 12.80v's):

1. Key on, no idiot light for the alternator illuminating when engine off
2. Pulled idiot light socket and found a bunch of corrosion on the spring contact - cleaned but still will not light with key on, not running
3. Took scotch-brite to bulb contact and still no light when key on, not running
4. Hooked a 9-volt up to idiot light bulb and it works fine
5. Checked voltage at idiot light socket and found NEGATIVE voltage

I assume I have a wire crossed on the alternator???

Re-check the alternator connection at the D+ (Blue wire).

[86 911 Targa]

here's the circuit.

[Joe Bob]

As above....your connection is suspect.

[Tippy]

Originally Posted by 86 911 Targa

Re-check the alternator connection at the D+ (Blue wire).

I saw the test in my manual regarding the blue wire to ground should illuminate the lamp. Depending on if it lights or not indicates what the issue may be.

The ring terminals seem to be mistake proof but maybe not?

I can't remember if the blue is the tiny wire or the medium sized one. I'll look today after work.

Thanks.

[john walker's workshop]

at the alternator, jump the blue wire to ground and if the dash light comes on, the circuit is fine. it's usually because one of the brushes is no longer contacting the commutator.

[Tippy]

Isn't the wires mistake proof?

There are 3 sizes and all of them felt like they engaged the post just right.

Gonna try the blue wire test and see if I am getting HOT to both sides of the idiot light socket too. I doubt but I'll double check.

[john walker's workshop]

you get 12v to one side of the bulb and the other side (the blue wire) initially is a ground wire through the alternator. once the alt gets charging, that ground wire gets hot and then you have 12V on both sides of the bulb which puts out the bulb.

[Tippy]

Originally Posted by john walker's workshop

you get 12v to one side of the bulb and the other side (the blue wire) initially is a ground wire through the alternator. once the alt gets charging, that ground wire gets hot and then you have 12V on both sides of the bulb which puts out the bulb.

Yep, the reason for my doubt and like everything I do, I am probably overthinking it.

[Tippy]

So,

1. Idiot light DOES NOT illuminate with key on, engine off
2. Ground the blue wire, the light DOES illuminate

Dead VR?

[Arne2]

Originally Posted by Tippy

So,

1. Idiot light DOES NOT illuminate with key on, engine off
2. Ground the blue wire, the light DOES illuminate

Dead VR?

Yes, that was exactly the case in my '84. New VR fixed it.

[Tippy]

What I'm thinking. Thanks

[burgermeister]

++ on new VR.

Pretty idiotic (pun intended) to have an alternator failure mode that does not illuminate the idiot light ...

[Tippy]

Ha

[john walker's workshop]

the problem is that the brushes on the regulator dig deep grooves in the alternator's commutator, so the brushes on the new regulator tend to be short lived because of the rough surface. the comm is thin and likely can't be remachined, so the best bet is to get a complete unit, new or rebuilt.

[Tippy]

Thanks John!

[burgermeister]

Alternators are pricey - no harm checking the condition of the commutator. (is it called that, even though it's not segmented like in a motor?). Mine was not grooved much at 150K miles - I cleaned it up a bit with thin strips of cloth-backed 220 sandpaper, and I've got 23K on the new VR without issues (knock, knock, knock on wood). I do carry a spare VR though ...

[Tippy]

Gonna tear it apart sometime this weekend and take a looksey. Hopefully I am just a VR away from charging.

Oh wait, I have wire up the entire MegaSquirt system before retesting......

[clarkd]

If you decide to polish the rotor slip rings/commutator then use sandpaper per earlier post. I recently went through an alt rebuild and was told by an old school alternator shop that using emery cloth will imbed emery and iron bits in the copper and trash the rings in short order.

[Tippy]

Hmmm, would have thought the opposite. Thanks.