Destroyed battery, the car or a fuse?

Replaced alternator belt. Had started the car with electrical cable (to alternator) disconnected to check for belt slipping/alignment. Ran for about 30 seconds and shut down. Went to connect battery cable (battery still connected) and was greeted with shower of sparks. Oops. Disconnected battery, ensured both alternator and alternator cable were fully discharged and went to reconnect battery. Shower of sparks again. Then I realized I had disconnected the positive side, not negative (how many hundreds of times have I connected batteries?). Crap. Disconnected negative, reconnected positive. Now the car is totally dead. No dash lights, let alone ignition, clicking sounds anything. Notta. Did I fry the battery or worse? Is there something like an 80 amp fuse protecting the car from mistakes like this? If so, where can I find it? Thanks in advance!

Check your fuses I’m not sure which one popped but the system is designed to blow a fuse first

Have you measured the voltage on your battery now? To determine whether it is dead.

Thank you for the reply. I was pretty disgusted with myself last night The voltage reads from the totally disconnected battery (about one year old, car, sitting idle for about two weeks, waiting on time and parts) read 11.64 Volts. So that�s probably pretty close to healthy, unfortunately. I�m assuming the Porsche engineers installed a massive fuse somewhere to protect the electrical system but I don�t know where that would be. It does not appear to be in the fuse box.

So what's the voltage if you connect the battery to the car and turn on the ignition or e.g. head lights? If it drops very low, you know for sure the battery is bad.

Yeah, the current distributor is located behind the dash on passenger side of car. you�ll need to unbolt positive cable then lower panel to open the case up and replace fusible links.

Power distribution box behind carpet passenger side foot well

THanks! Not sure of what the current is with the car still connected. I immediately disconnected everything. The dash was completely dark. I'll look for that in the passenger footwell at after work tonight. It's called the "current distributor?" Standard blade fuses 50A, 80A? I'll pick some up.

This should help: https://www.renntech.org/topic/12521...utor-location/

Yeah�50 and 80 amp fusible links. Will most likely have to order or call a dealership. Porsche specific.

I'm not an electrical engineer but I can't figure why a disconnected alternator would cause the issues you're having. To have a "shower of sparks" I think you would have to be reversing polarity somewhere, or else have a dead short that is drawing mucho amps. Do you have a battery tender or charger? Maybe try hooking that up to the battery and see what it thinks. Isolate the battery from the car circuitry first.

A blown diode can fail in a short condition, and cause some pretty hard grounding shorts.. Same if a armature shorts out in the alternator..

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Yep, my thoughts exactly....OP, I think you killed the alternator.. Alternators do not like to be ran on "open circuit state" ..They like having the battery in the circuit to act like a big capacitor to absorb the voltage spikes , plus they use the feedback from the battery for control of the voltage output.. It's never a good idea to run a modern car without a battery, or with the alternator disconnected from the battery ....

Rear panel 1 My car was highly modified by the previous owner. This is a pic of the fuse panel behind the rear seats. The large red and green blade fuses look intact. I assume the large square items are relays? I haven�t taken the passenger side dash apart to check for a fuse panel behind the HVAC Blower yet. Rear panel map

The disconnected alternator was ran for under a minute but probably was in a charged state. That was dumb. The negative battery cable was never removed (also dumb) so I don�t think it�s a reversed polarity situation. The dash lights would not even come in at all after the incident so even if I fried the alternator, I would think the battery would allow the dash lights to come on. It certainly started the car without the alternator minutes before the spark show. It seems a blown protective fuse is the most likely culprit- the question is where and what does it look like?

Y ou won�t have to dismantle your dash to lower the current distributor. You will have to unbolt the positive cable from the firewall . Attached with a nut that is located in the frunk. You�ll need to lie on your back in an uncomfortable position to remove the distributor from passenger footwell, all fusible links are housed in white plastic holder or distributor. If cable from battery runs continuously to parcel shelf behind seats your car may have been modified and the links done away with.

If you had a massive shower of sparks, it�s possible a cable is the culprit. I would use a multimeter on the resistance (ohms/continuity) setting and test your main power cables. Do this with the battery disconnected from the car. Come to think of it, the same continuity test can be done on the fuses as well.

Try taking the alternator out of the circuit again. Don't start or run the car! Just remove the alternator electrically. Then see if you still get sparks.

This is what u r looking for. Follow the 12+ back to the firewall in the frunk, disco it and the 2 bolts and u think it will slide out past the hvac box if u cant access it. Use a multimeter to test.

Thanks Aaron! Multimeters are Chinese to me (literally and figuratively) but I'll take a crack at it. Yep, I definitely have one of those between the HVAC blower motor and firewall. What is that called? It can be removed without removing the HVAC blower box? I'm looking for something that looks like a big fuse or relay? Or something that looks melted? thanks again.

In the second pic the panel in the middle snaps out and thats the fuses. These r the main high amperage fuses. If the car has no power at the fuse box un the footwell then there has to be an issue here. I think it can be pulled without removing the hvac box. The 1st pic shows the power lug and the 2 bolts that bolt it to the firewall. Multimeters r easy. For about $40 u can get one at Lowes. Set it to Ohms and the leads should chip/beep when touched together. This is called continuity. Now u can touch each side if the fuse to see if its good. U can also use it to check for voltage. Set it to dc voltage, ground the black wire and then probe both side of the fuse to see if the voltage is the same on both sides. The bigger issue is figuring out what dead shorted and caused the fuse to blow. (If thats the issue). As said earlier u may want to disco the heavy wire on the alt and make sure its not shorting out.

Here is a pic of the fuses. U may be able to test without removing the box. The fuses can be bought off amazon.

Thank you everyone for the responses. got the electrical issue resolved!

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So what was the dumb thing that was wrong that u dont want to tell up about?

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Curious minds want to know.

Dumb thing. It�s got a LS3, probably should have started with that. RH conversation kit. The alternator bracket is less than robustly engineered. To provide tension on the belt, the alternator is supposed to be shimmed with five degrees of off-axis tilt. It eventually sheared off the rear M10 bolt�..so not the best solution. Installing a better bracket, I�d totally disconnected the Powermaster alternator (has connections for four pin or single bolt, mine used single bolt in cable). Hooking it all back at a different angle in the middle of the night, I connected it to the wrong -actually reversed polarity on the alternator, didn�t realize till next day. Cooked the positive lead coming off the alternator.

Yup, dumb .

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So did you buy that guys custom ECU tune that lets the LS computer talk to the car and makes all the gauges and stuff work?

There�s two complete conversion kits: Renegade Hybrids and Chavis Performance. Mines is RH. ALL gauges work, AC blows cold. The previous owner was tracking it but I�m a complete poser. Daily driver for summers.

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I am intrigued by these well-done swaps. How long have you had it? And any issues? Are they still around $30k turnkey?

The CPE cars (mostly 997.1s) are trading hands for $60k+. I didn�t pay nearly that. I bought my �99 C2 w a new LS3 crate engine-about 135k on chassis, ~5k on motor . Gearbox was replaced by Porsche around 126k, so the original M96 engine was swapped not long after by a PO. PO tracked the car-half cage, fixed back seats, 6-point harness. I swapped the interior from red to black, installed sound proofing, & installed leather/carbon fiber Cobra Misano that accept 6-point harness. Had exhaust rebuilt w cut-cut outs and tuned the LS3 engine. Street use only, lots of fun, put about 15k more miles on it. Only real issue was the alternator- the RH kit bracket isn�t well designed. Originally aluminum (cracked) then steel (flex allowed a 10mm bolt to shear off). Went w a robust 10mm thick billet bracket from another vendor. Once I get the right size belt (33.25�?) I think that will end the issue.

One day ill get to see my old interior at the track........ we need to meet up at mid-o or pitt race next year and shread some tires.