Connected battery the wrong way
 

:Ok, a friend of mine just rang and said that he just connected his battery the wrong way round.

It's a 1977 911S.
It made sparks.
He said he could smell that burnt electrical smell in the engine bay.
He corrected his mistake but says it starts and runs fine now but the alternator light stays on.
Even when the car is off and the key is out.

How much damage has he done??

Cheers,
Frank

Maybe trashed diodes in the alternator/regulator?

^^^^ This. BTDT. Just pull the alternator and get it rebuilt.

The above is probably correct, but before pulling the alternator it's easy enough to check whether the it's working - just measure battery voltage with engine running. Not sure I'd trust the alternator light to be working correctly given the reversed polarity incident.

Yep. measure the voltage then you’ll know the alternator’s status.

Odds are a diode has fried in the alternator as current flow is being shown at the lamp with the key out.

Hopefully just flowing up the blue wire via the alternator bad diode and finding a ground through one of the instruments or gauges, as normally the balancing 12 vdc to the lamp is switched off with key out and the blue wire sees no voltage until the alternator spins.

Probably should inspect the red/black wiring at the gauges.

Thank you for the information and advice.

I'm going around to his place shortly to remove it. He tells me that he is taking it (the alternator) to an Auto elec to have tested and rebuilt
Thank you timmy2 for the gauge wiring inspection tip.

Cheers,
Frank

Hopefully he caught it quick. I’ve rebuilt/replaced dash and engine harnesses from this type of event. You’ll know a lot more once you start pulling the alternator.

I haven't looked at the dash yet but melted solder fell from the alternator when we got it out.

Here is a pic of one of the diode posts gone.

And , the regulator? Been consumed by mice.

Bothell are going to an auto electrician today.

Thank you for the assistance.http://forums.pelicanparts.com/uploa...1631148604.jpg
http://forums.pelicanparts.com/uploa...1631148604.jpg

How come it’s always are “ friends” that do stupid ****?

🤣😂🤣don't worry, I do stupid **** too, just not this one.😉