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post #1 of 8 (permalink) Old 18-11-2012, 19:09 Thread Starter
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Battery to ecu earth cable

I was re fitting my battery and when I was tightening up the live terminals the end of my rachet touched the ECU and caused sparks made me jump is an understatement so I looked around and found a thin wire connected to the ECU case and the negative terminal on the battery, it doesn't look like it was ment to be there but I don't want to remove it in case it is ment to be there

My question is should it be there, if not why would it be there
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post #2 of 8 (permalink) Old 18-11-2012, 19:12
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It's probably there because someone did what you just did with the spanner and burnt out the internal earthing of the ecu

usual situation is that the ecu won't power up then without the casing earthed (or internal repairs made) but usually the former for convenience. It's quite common advice in this situation to route a wire from ecu case to chassis or battery negative.

Important question, does your car still run? If so, you're in the clear. I don't want to know what your ecu smells like inside though.



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post #3 of 8 (permalink) Old 18-11-2012, 19:19 Thread Starter
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Ah I see, but yeah all runs and everything works first thing I checked lol, didn't really smell at the time but I don't know about inside

Guessing if it still runs and all works then I'm in the clear and it won't blow up next week, note to self now "use smaller rachet/spanner" lol
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post #4 of 8 (permalink) Old 18-11-2012, 19:22
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It's a silly place to have an ECU to be honest. Swing too far and it's death by arc-welding

But yeah, if it runs then breathe a sigh of releif



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post #5 of 8 (permalink) Old 18-11-2012, 19:35 Thread Starter
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Phew I like the in the clear part especially as I have just spent the last 2 days rebuilding the whole front end and new rad
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post #6 of 8 (permalink) Old 18-11-2012, 20:56
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Is it worth fitting an external earting strap to the ECU as this may save the internal link burning out during a "mishap" ?
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post #7 of 8 (permalink) Old 14-02-2017, 09:04
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Sparking the alternator is always fun. Hope your ECU is ok.

Shouldn't really earth to the battery (-) terminal though. Should be to the car chassis which has a larger capacitance and resistance (less chance of giant sparks).
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post #8 of 8 (permalink) Old 14-02-2017, 17:43
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You should disconnect the earth first and reconnect the earth last. That way you will not get a risk of shorting the battery terminals to the frame of the car when removing or reconnecting the battery.
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