Electrical fire in Alternator when installing battery

[75 Westy FI noob]

When I connect my newly charged battery … sparks fly at the negative terminal and my alternator immediately begins to flambe.

Smoke pours from the front of the alternator, and it’s definitely electrical.

I havent changed any main wires.
Ive only cleaned up the connections on the new brake lights.

I was at the finish line (brake lights was the last thing)
Now im at the starting line.. flippin electrical fire and a lost alternator.

i dont understand how it could happen .

[alman72]

these old vws have funky colors on the cables. confirm what you thought was negative is bolted to the body. i think i had clear and black? and black was positive.

[Abscate]

Either positive on the alternator is touching ground ( common) or you reversed polarity. Double check battery connections. Red is not positive.
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[75 Westy FI noob]

Thanks guys… i will double check the polarity.
I was focused on the batt platform, may have gotten them flipped.

Think the alternator is toast?

[Abscate]

[75 Westy FI noob]

I double checked my battery… i had the leads right.
Ground was to Negative like it should be etc.

I haven’t messed w the alternator wires. Those are all bundled and in the case. I dont see how it could get grounded. cars been a peach.. starts and runs well. just needed brake lights. Yesterday i removed the battery to charged it. installed the brake lights. Cleaned a ground connection inside engine door on the right. and put the battery back in today. immediate smoke. No key.

Btw, tail/brake lights still dont work.

[crownline]

Check the terminal posts for the correct length. Compare to original alternator. If the posts touch the tin=ground
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1972 Bus 1700 cc Single Carb. But not a progressive.
Barelymuvin
Wish I still had the ones I got rid of.

"It"s got some dings and dents and neither of us is going to SEMA."(Update, I went to SEMA in 2019 but the Bus stayed home)
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[75 Westy FI noob]

[sjbartnik]

Forget about red and black. Cable color does not matter.

From the factory there is no red main battery cable. The + cable was black, and the negative cable was a woven copper strap.

The positive is the one with the wires that got to the starter and up front to the fuse box.

The negative is the one where the other end is bolted directly to the body next to the battery.

Sounds to me like you connected the battery up backwards.
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1965 Volkswagen 1500 Variant S
2000 Kawasaki W650

[Abscate]

It’s not only reverse polarity, 11.7 Volts is A dead battery
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[75 Westy FI noob]

Got that … it was connected correctly.. positive to the +

But, my battery itself seems to be reversed polarity.
I seem to have reversed it when I charged it overnight.

[Alan Brase]

You charged the battery backwards. Once it is dead, lead acid doesn't have any memory. Drain it to totally dead. with lights or something. then hook charger up correctly.
You killed the alternator.
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Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home

[Wildthings]

Don't really know how much of a life one would get from a battery that had been charged backwards, while you could run it down using a headlight or other moderate load and then recharge it to the correctly polarity, I would tend to spend the money to buy a new one. Hate to be stuck on the side of the road over a few dollars saved, while a battery blowing up could end your Transporter Joy.

[75 Westy FI noob]

I got a new one.. put it in. Saw some sparks connecting the - .. and i think the Alt even jumped… but no smoke. And the tail light, tag light, and blinkers now work.

Im hoping the Alt will sill work. Slim chance I guess.

[Wildthings]

[75 Westy FI noob]

[W1K1]

if you have a local motor rewind shop, you can take it in and have it tested and repaired if you just fried the diode or the internal regulator
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http://www.thesamba.com/vw/archives/manuals/jim_martin_engine_build.php

1973 super
1965 squareback 1500E
1971 bay window westy- subi swap

[Alan Brase]

[75 Westy FI noob]

[mikedjames]

Until you run the engine you will not know about the alternator.

However - if you disconnect the positive feed from the battery to the alternator, and disconnect the regulator from the alternator so nothing else is connected.

Then put your meter on diode test and connect the positive lead to ground, and the negative lead to the battery B+ connection of the alternator, it should read about 1 to 1.4 volts drop - being two diodes in series.

This is also true for the warning light D+ connection, it too should read 1 to 1.4 volts drop on diode test.

If both of these show about this voltage drop on diode test, then it is likely that at least two of the six diodes in the main B+ rectifier are good, and the same for the D+ terminal.

If you connect the battery backwards (or a reverse charged battery) and the alternator was smoking then you probably blew the diodes in the alternator.

These are replaceable but there is a reasonable amount of work hours to get at them and replace them.

I blew a Hitachi alternator on my boat engine connecting a battery the wrong way with jump leads -- and was able to replace the diode pack inside .
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Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy