Connected jumper leads in reverse and now no power - AUSJEEPOFFROAD.COM Jeep News Australia and New Zealand

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Old 21-07-2018
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Last edited by AD007E; 19-12-2018 at 09:24 AM.
Old 21-07-2018
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clean your battery terminals
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Old 21-07-2018
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I'd say you've blown a few circuits breakers, fuses and if the Jeep has then, fusible links
My mate did the same to my MR2 years ago and it cooked a heap of fuses and fusible links

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Old 21-07-2018
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Try taking the old battery out of circuit by taking the positive lead off and connecting it to the jumper lead. You may have damaged the old battery and it is dragging the system down. If the engine starts put the lead back on the old battery with the jumper lead still connected. DO NOT run the engine without a battery connected.
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Old 21-07-2018
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or try a different battery
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Old 21-07-2018
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If you lucky than the pcm is still ok. In some similar cases pcm can burn out before any fuse goes .
It sound like you trying to start the engine with a week battery .
Once battery voltage level fall around under 11 volts that battery is cactus and any further atempts to charge it will just give only a surface charge on the internal plates but not a deep charge and it just would not have the cranking power required for starting .
Just get a new battery and if it fires up than you lucky and the PCM is still ok.
Of course make sure fuses are ok .
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Old 22-07-2018
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Originally Posted by AD007E View Post
Hi Team,
Need some help with this one, have been away for four weeks and went to start my 95 and the battery was dead flat. went to jump start and accidentally connected the leads reverse polarity for a second, sparked a little bit.
When I did similar on a non-computer vehicle, it fried the alternator diodes.
The alternator is now a short-circuit...sniff it

My understanding, reversing voltage on a computer will likely destroy it.

Your symptoms replicate a shorted alt or dead PDC

I would obtain a used PDC and alternator from a wrecker and replace them

The PDC must come from a similar pre or post 97 (immobilizer) and auto/ manual

reversing voltages will not normally blow a fuse

(little known fact...a dead flat battery can fully charged in reverse polarity, will power up a headlight, even spin a starter
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