AnswerID: 244095 Submitted: Friday, Jun 01, 2007 at 22:09
Grungle
replied:
A big thanks to all of you who have replied. It means a lot and I do apologise if I don't get back to you all.
Aside to the problem:
I have pulled the torch out and tried to find out why this happened. Discovered that the connection from the negative terminal of the battery to the earth point of the winch was resistive due to not being done up properly at the winch. Found the bolt that connected the terminal to the winch casing was half done up and the cable was free to move (hence why it was the first to spark). This meant that the earth return for the winch went along the chassis rail, through the handbrake cable (which is the flexible steel conduit I mislabled as the speedo cable) to the transfer case then back along the gearbox, motor and then negative terminal of the battery via the body / motor / battery earth cable.
There was a small 6mm² cable that earthed the winch control box to the body which vapourised due to the current involved. It looks like this was the inital return path but after vapourinsing, the earth returns next path was via the chassis rail and gearbox / motor.
I had the vehicle running at the time but I can't understand why the earth return didn't go along the chassis rail and through the earth cable that connects the battery neg to the body. Is the body and chassis rail earthed together? If not then this would explain why it went through the motor and gearbox.
As the handbrake cable is the thinnest connection between the chassis rail and motor, this would explain why it glowed like it did. I would say that there would have been between 100 and 200 amps across it.
Hope to see more in the morning. I have an auto elecy friend coming around first thing to help me do some checks and see exactly what has been fried (physically and electronically). I am dreading the dash and pray to god that it was a single wire that decided to vapourise (touch wood) and it easy to find.
Will let you all know how it turns out.
Again thanks.
Regards
David
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