Parasitic Drain - Bulb Trick

Nov 11, 2006 22 Replies

...and be careful. If you by some mischance get it across the battery it will try to dissipate I^2*R W. One ohm at 12V passes 12A, so thats 144W, well in excess of the 10W its rated for. It will get red-hot and fail in some interesting way, quite suddenly...

Nigel Spon wrote in news: snipped-for-privacy@kyle.snap.net.nz:

So,if you're that inept,put a 3A fuse in series with the resistor,like many DMMs that are fused for the current ranges.

Of course,any ammeter would also be a short across the 12V.

Hello again, I was the original poster of this thread. I'm posting an update to the problem, for those who are interested.

After disappearing mysteriously, the parasitic load was back again last night. Today I've finally found the problem. It's the *alternator*. I found it by disconnecting the alternator ground. It was very hard to find before because it was intermittent, but it's definitely the alternator.

Bad alternator diodes..? I recall the problem started just after an engine wash..

Thanks.

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