Car Wont Charge + Melted Alternator Ground: Why?

euro911sc · euro911sc's Garage

Car '82 SC w/ 3.0

After the car was laid up for wheel bearings and new AGM lightweight battery install, the car would not charge. It would run fine under full battery. I checked grounds at the battery, the transmission. Battery ground was loose so I tightened it with no solution. The alternator was brand new last year with maybe 1000 miles on it at most. I pulled the alternator and found this:

Now, early on I did find that the battery ground was loose. My theory is that the battery ground was not connected well and the alternator/current then tried to use the ground to engine as the main ground thus over heating this wire and killing the connection. Then I fixed the loose battery ground, but it was too late for the wire and now it wont charge.

Now this wire was not broken and still had continuity to the battery ground. Just the sleeve was melted. The wire itself remains conductive.

I have pulled the alternator and will take it to the FLAPS to test it. I will also replace the fried wire.

Thoughts? Do you believe I have found the culprit? Or just another symptom?

tharbert · tharbert's Garage

Check your transmission ground strap?

DRACO A5OG · DRACO A5OG's Garage

Test it at two different FLAPs or at an alternator re-builder. Just to make sure the testing equipment is accurate. Ask me how I now.

Proper ground is critical, you may have found the culprit.

wwest · wwest's Garage

Your starter motor/GENERATOR(!) remained engaged once the engine was running.

Common result.

DRACO A5OG · DRACO A5OG's Garage

Quote:

Originally Posted by wwest

Your starter motor/GENERATOR(!) remained engaged once the engine was running.

Common result.

Oh my

, just to be safe maybe check it as well.

mspirito · 06-21-2014, 11:50 AM

If the starter motor remained engage would it not be heard, be somewhat obvious? Or would it going to take a short period of time?

KNS · 06-21-2014, 12:56 PM

I had an old Honda with a starter that would sometimes stick and stay engaged. It wasn't loud but you could hear it if you listened.

One time it stuck and I didn't notice. I drove off for several miles and the starter was smoking.

euro911sc · euro911sc's Garage

No smoke no smells. Its a high torque starter that was rebuild 2 years ago. has maybe 8000 miles on it. I'll check it, but I'm doubtful.

FLAPS could not check the alternator correctly. No pulley and their system told them to use a connector that made no sense at all. When I had my last alternator rebuilt at a local shop they had the same issues. No pulley no testy.

I replaced the wire and checked all the ground straps/connections on the engine/trans/and battery. I'm re-charging the battery now and will let you all know what happens in about an hour.

I suspect that the alternator voltage regulator is toast. No signs of damage on the alternator, though... bummer if I have to spot $400 for another new alternator... sigh...

47silver · 47silver's Garage

Alternator needs to duty cycle to stay alive, your loose battery ground Would make the alternator v/r think that the battery was dead and it would engage and operate 100% of the time. Chances are very high that the alternator has failed. I would have it rebuilt at a shop

DRACO A5OG · DRACO A5OG's Garage

Oh no us Pcar guys have to bring our pulley halves with us so the FLAPs can put a belt on it. Yeah, unfortunately some of the FLAPS guys really do not know what they are doing so that is why I wrote go to several FLAPs to double check.

In my case, two different FLAPs had two different results, I went to a re-builder to confirm it dead.

$80 later all is well with life time warranty on re-build

Quote:

Originally Posted by euro911sc

No smoke no smells. Its a high torque starter that was rebuild 2 years ago. has maybe 8000 miles on it. I'll check it, but I'm doubtful.

FLAPS could not check the alternator correctly. No pulley and their system told them to use a connector that made no sense at all. When I had my last alternator rebuilt at a local shop they had the same issues. No pulley no testy.

I replaced the wire and checked all the ground straps/connections on the engine/trans/and battery. I'm re-charging the battery now and will let you all know what happens in about an hour.

I suspect that the alternator voltage regulator is toast. No signs of damage on the alternator, though... bummer if I have to spot $400 for another new alternator... sigh...

wwest · wwest's Garage

Alternator output self limits at maximum current rating. Open battery connect would result in extreme high voltage and boiling electrolyte in short order. But with poor battery ground of a decent resistance the only result might be blown electronics due to extreme voltage.

In any case it appears most likely that the starter was GENERATING.

euro911sc · euro911sc's Garage

47Silver I think you are right here. Looks like the Alt must be dead. I'll have to pull it again and take it to the shop. What a PITA! By the time I'm done I'll be able to pull an alternator in 10 minutes or less.

euro911sc · euro911sc's Garage

On closer inspection: Alternator totally fried...

Note the skewed piece between the two yellow marks. There are 6 of these and 4 are melted off their connections. I have found the voltage regulator on-line, but I am not sure I can find those assemblies to replace the melted parts.

Damn...

steely · 06-23-2014, 04:39 PM

maybe a dumb question, are those the diodes?

304065 · 06-23-2014, 06:12 PM

Uhh, a missing ground wire does not tell the VR to charge. If the alternator D- isn't grounded, the alternator CANNOT charge, you don't have a complete circuit between the output diodes, the battery and ground.

What that looks like to me is that the ground wire contacted the B+ terminal somehow, shorting it out. When it shorts, it heats up and cooks off the insulation.

When you reinstall the alternator, make sure none of the wires are touching each other.

47silver · 47silver's Garage

i think he said that the battery ground was loose not bad. I may be wrong, but if the circuit was not operating at 100%, then the voltage would be lower thatn what the v/r wanted so that alternator could be working overtime to compensate.
Wouldnt it be like having a partial battery?

Gene Smith · Gene Smith's Garage

I would re check the big strap ground and the negative side of the battery.

It looks like all the current was passing through the little alternator ground because of a lack of (big) ground between engine and battery. Check the battery negative post terminal, the negative cable to chassis, the transmission ground strap and where the strap attaches attaches to the chassis.

One of those BIG grounds is likely loose or corroded.

euro911sc · euro911sc's Garage

Quote:

Originally Posted by steely

maybe a dumb question, are those the diodes?

I have no idea... are they? I'll be at the shop in about 30-40 mins. I'll ask then

47silver · 47silver's Garage

the guy who rebuilt my alternator showed me that the original porsche alternators used pressed in diodes, where-as the rebuilts use soldered free floating ones. if you are getting a shop to rebuild it ask him if he has the pressed in ones

steely · 06-24-2014, 06:37 PM

Quote:

Originally Posted by euro911sc

I have no idea... are they? I'll be at the shop in about 30-40 mins. I'll ask then

No alternator expert here, but they look like they were press-fitted into the top plate, and the wire-like item that is between the yellow markers looks like a lead. There may be 6 - and the effers took a beating if they all look like the one on the left. The stator may have overheated during this process and could be suspect. The VR is electrically between the diode (bridge) and the load (batt /starter). I would be interested in what you guy said.