DB 1490 electrical problems

[marcusthehat]

Having recently fitted a new battery and heater plug a week or so ago, yesterday evening, after working for about 3 or 4 hours, smoke started rising from some of the wires leading to the ignition switch, I figured a short somehow, & got the offending wire pulled away from its neighbour, at which point the smoke stopped.
I drove her home, say 15 minutes, without issue or smoke, checked she would re-start, parked her outside and disconnected the battery.
Started her this morning to reverse into the shed, all seemed good, but on looking forward again, more smoke, from the same wire.
So I pulled the various wires from the back of the ignition switch and then disconnected the battery, before investigating any furthur.
The plastic on the heavy brown wire running from the battery via the solinoid was melted, between the ignition switch and the solinoid connection, but nowhere else.

I have down through the years stripped out all fuses and apart from a solitary freshly run wire from the accessory lug supplying current to a 2 pin socket to work the wee forestry winch(i.e. PTO driven but electric hydraulic valves, so no big current draw) the oil pressure light and the charging light are the only working electrics, aside from the charging/starting circuits.
The single wire to supply the 2 pin socket for the winch controls, shows no signs of excessive current draw or heat, nor does any other wire cept the single melted brown one, and the exposed copper, beneath the melted plastic, is bright and fresh.
So
Why?
What is likely to be the issue?
Obviously I intend to replace the offending wire and connectors, but what could have been causing such a heavy current draw, since it was apparently not a dead short.
marcus, the preplexed

 

[Mursal]

Ignition switch shorting out inside?

Disconnect all output wires (if you can) and reconnect the supply to the ignition switch with just a few strands connecting it to the solenoid terminal. The few strands will act like a fuse, so work the ignition switch hoping to blow the fuse. Switch will need to be mounted as it was originally, no good testing and the switch in your hand.

 

[marcusthehat]

Ah!
But,
My ignition switch is "free floating", being supported by the various wires only, 2 being replacement heavy relatively stiff wires, (think cooker cable, well almost) because I actually ran another fresh wire to the solinoid/starter + the previously mentioned new wire for the winch supply, from the accessory terminal.
And I support the switch body with my free hand when turning the key.
So nothing to "short" to, that I can figure.
Its all 12V +ve
cheers
mth
****
but I will try your suggestion am tomorrow mursal,
since my first ever space heater was delivered late this afternoon.
no more frozen fingers, hopefully.
mth

 

[marcusthehat]

Well, I started after lunch, stripped out the melted wire, and ran a fresh 7 strand "cooker" wire back to the old/origional ignition switch, from the solinoid +ve spur, then reconnected the heater wire and the starter wire and tentatively touched the disconnected battery terminal to the post, zero sparks, so no current draw, ergo no dead short for sure.
So reconnected batt terminal and started her.
100%
cept the alternator charge light has decided to not work.
sigh
might hafta buy that Valtra 6400 yet.

I can only presume that the +ve wire, somewhere between the solinoid and the ignition switch had worn through the insulation and was shorting to earth, but then why melt downstream of the dead short, or between the short and the ig switch.
Between the dead short and the +ve supply I can understand, but not on the other side of the short.
mth
P>S>
Quite magic basking in the 20.5kW space heater output, not long of softening the stiff almost frozen insulating tape either!

 

[Mursal]

Good you got sorted .................
Are you OK checking out the charging warning light?

 

[marcusthehat]

I should be . . .
It is the last remaining light working in the dash, the oil warning light is a bulb sprigged in on top secured with a cable tie.
And it was working when I brought her into the shed.
So I must have disturbed sommat, which I shall investigate in good snow-reflected day-light tomorrow.
Anyway I am only up the Moss, and since a pull-to-stop IP control, I should suss a lack of charge if the winch controls stop working, and still be able to drive back.
P.S.
A lot of the origional DB wire insulation has got very hard, and cracks through to the bright copper if bent or disturbed, so I could be tempted to fall-to the remains of the defunct loom with a pair of side cutters.
cheers

P.P.S
The reason for the "free-floating" ignition switch was to move it nearer the pull-to-stop control, inside the LHS door, for ease of stopping and starting whilst on stationary PTO work, without having to clamber up into the cab.
MTH