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So, I bought a batch of batteries to change out in some cars since I am all out of other projects. The 2008 Cayman (base) was the last one and I stupidly, installed in backwards, having taken the old battery out for the core chg. My excuse is that the other two had the negative post on the left...

Anyway, I started to attach the pos cable and yanked it as soon as I realized what I had done. I was pretty much scared *****less knowing this is a computerized car. After reinstalling the battery correctly, I started the car, no problems except that it had to re-learn some things and the radio was dead. I drove the car about 10 miles to make sure everything was OK and it seemed to be. I assumed I fried the fuse to the radio (stock) but did not realize the fuse is on the rear of the radio frame. So, I started pulling fuses looking for the radio fuse and to make sure I didn't blow anything else. After finding all fuses intact I realized the radio fuse was not on the panel. I then tried to re-start the car but every single fault alert lit up, brakes, ABS, PSM, etc. and the cooling fan for the front rad came on, I'm sure because an overheat fault was registered. No crank of course.

If I damaged the ECU or sensors, why did the car start and run perfectly? I am sure I replaced all the fuses correctly when I went through them and double checked them all a second time. I found the fuse diagram on the web and it looks like I DID replace them all properly. I feel as though I am missing something that should be obvious. Before I flatbed it to a shop I want to feel like I'm not blind to something I should be seeing. Photo of my fuse panel below, in case someone can point out that I mis-placed a fuse. 2008 Base Cayman, Manual, CDR24 stereo

Thanks if anyone can help or has advice. Darwin
20200417_183536.jpg
 

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Had a battery installed backward in my 2011 Cayman. Only real problem was alternator was cooked. Drove OK for a few hours then warnings and problems started popping up. New alternator and all is good.
 

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Thanks, how did you figure out it was the alternator? I have a no crank so cannot test. Every single possible failure lights up, the chimes get really loud and the cooling fan kicks into high.
 

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You may have a different problem mine fired up. Just weird things happened most likely due to voltage changes. Warning lights came on. Radio in and out.
 

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Haven't done this to a P-Car, but did this to a Ford Taurus once on my family's little used car lot. Didn't realize they'd brought us the wrong unit (right size, poles reversed) and wasn't paying attention. It was...dramatic. Trunk lid flew up from the electronic release, horn went off, fuses popped. There may have been smoke, but it was over a decade ago and my memory is hazy.

Dad was not thrilled, but a few new fuses, an alternator, and a solid chewing-out later it was just fine. I now double-triple check batteries when replacing. Thankfully modern electrical systems are reasonably well protected against stupid crap like this so in most cases you'll not fry an ECU or something. Still sucks having to change out an alternator, but it beats expensive electronic boxes.
 
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