Attention All Puma Owners

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Originally Posted by Iain_B

My first thought as well Jim - if you shorted out to the body Iain, the handbrake cable will do a great job of acting like an earth cable for a few seconds. I thought the handbrake light goes to earth when the handbrake is on - so worst that would happen is it would turn the light on it if shorts out.

I have made sure the body on the truck is properly earthed to the chassis - don't want all the little wires or cables being the primary earth if something happens to the main earth.

One known problem on older Jaguar V12 is that the earth strap corrodes, then the accelerator cable becomes the earth strap, and on some the accelerator cable runs under a fuel line :eek:

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Yep after receiving Jim's pm I got to thinking he is right, as the contact was made with the seat box it probably found the handbrake cable as the shortest path to ground.

I dont think that the battery is directly ground to the body in the battery box. A job for the to do list this week!

The exact same electrical fire engulfed the cabin of my Puma about a month ago, complete with snapped handbrake cable and reduction in number of remaining years to live.

Unfortunately mine happened after the battery broke free in the battery box during an excursion off road whilst touring one night. As a result I didn't realise it was shorting until the handbrake cable grommet was well alight.

Initially I thought the whole under-body had gone up and the flames were just lapping through the handbrake assembly rather than being the point of ignition. A lot of possessions were thrown out of the car at great pace for no reason! It was extremely relieving when I realised it was only the handbrake that was alight.

I'm confused, why does a positive short to the seatbox go through the hand brake cable to ground when the seatbox is bolted to chassis mounts?

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Originally Posted by manic

I'm confused, why does a positive short to the seatbox go through the hand brake cable to ground when the seatbox is bolted to chassis mounts?

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I would think that the seatbox - handbrake cable - handbrake - engine - battery would be a conductively better path than body - chassis - engine - battery?

If the negative terminal is ground to the chassis and the seatbox is bolted to the chassis I would NOT have guessed that the handbrake cable to the transfer box route is the least restrictive.

I would have guessed: Seatbox - mounting bolts - chassis.
Good job I'm not an electrician.

Anyway perhaps the best thing to do to prevent this kind of short is to line the battery box with rubber and have a rubber mat that sits on top of the batteries. That way even if something comes loose it would be hard for it to short out.

Of course you would still need to be careful removing the terminal connections with a spanner! Remember negative terminal first :p

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Originally Posted by manic

If the negative terminal is ground to the chassis and the seatbox is bolted to the chassis I would NOT have guessed that the handbrake cable to the transfer box route is the least restrictive.

I would have guessed: Seatbox - mounting bolts - chassis.
Good job I'm not an electrician.

Anyway perhaps the best thing to do to prevent this kind of short is to line the battery box with rubber and have a rubber mat that sits on top of the batteries. That way even if something comes loose it would be hard for it to short out.

Of course you would still need to be careful removing the terminal connections with a spanner! Remember negative terminal first :p

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Sorry yes I added the engine into the second route which it wouldnt be, but still it would take the path of least resistance and the distance between the point of the short and the handbrake cable was probably less than the distance between the short and the chassis bolt and back to the terminal?????

Im thinking out loud now so if there is someone with a qualified response :angel:

Im thinking out loud now so if there is someone with a qualified response :angel:[/QUOTE]

I too would like to hear from someone qualified about this.

Maybe as Chook73 said another lead from the body to the chassis to ensure a proper earth.

Jim.

I won't say one way or the other about my qualifications, other than there are people about without formal qualifications that do know something. :)

I would be looking at the all the existing earth points first, to see if any of those points need their point of contact cleaning of paint, rust and / or anything else that is resistive to current flow.
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Originally Posted by wrinklearthur

I won't say one way or the other about my qualifications, other than there are people about without formal qualifications that do know something. :)

I would be looking at the all the existing earth points first, to see if any of those points need their point of contact cleaning of paint, rust and / or anything else that is resistive to current flow.
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Yes I agree,but is there a dedicated earth between the body and the chassis or just that its all bolted together so it should earth somewhere?

Jim.

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Originally Posted by yt110

Yes I agree,but is there a dedicated earth between the body and the chassis or just that its all bolted together so it should earth somewhere?

Jim.

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Whether there is or there isn't, it's looking pretty clear that the lowest resistance path to earth from the body is the handbrake cable - which is concerning to say the least (particularly as I shorted a battery the other week myself :eek:).

As a former electrical fitter/mechanic I'll be doing some serious investigation in this on the weekend.