I had a rear bulb blown, so i replaced it and pushed in the new bulb.

turned the ignition on

tried the lights no rear lights at all.

smoke comes from under the dash and the rear light fitting so i pulled all the fuses.

the light fitting had shorted and fused, the dash stalk stuck and had to be tugged free, so i assume that it is un servicable?

removed the light bulb and replaced the fuses, the lights at the front work but no rear lights at all.

if the front lights work would i be right to assume the switch on the column still works?

and also right to assume that the light fittings need to be replaced to work?

ditch

If you had smoke under the dash then good chance you have damaged some of the wires under there and melted them . Get yer head under there and have a good look

If the fuse(s) had worked there would have been no smoke from burning wires. They need to be rated lower than the cables they protect. Sounds like the wire to the rear lights has burnt out.

Go luck with the repairs.

do a continuity test to the rear lights if the fronts work this would signify the switch is operational and damage to either the wiring or light units

Sad to say with a scratch built car with scratch built wiring theres no advice or check here for this type of advice that anyone can give without seeing the problem, so your on your own sorry to say.
As for fuses a fuse is designed to carry current if a fire starts through a short or any other reason and the current doesnt rise above the fuses rating the fuse does nothing but let the current flow and lets the fire continue, a fuse does not protect against fire.
This goes for fuses in a vehicle in your house or wherever including RCB's or whatever protection is in place. The only safe way to protect against electrical fire is good design and regular inspection.
Cheers,
Bob

Sounds like you have full load going through the column switches, some can take it, some can't, I always use relays

thanks lads

i checked this morning in the day light and the cause i beleive was my error in putting the wong bulb in and the two live terminals (for a tail/stop) earthed out on the bulb casing (i really must spend more time thinking things through before acting especially when trying to do quick jobs).

the light fitting looks the worse for wear so will need replacing and i will look under the dash for singed wires.

the loom is a vickki green loom and the fuses are as original, so i am not sure why it has done this. but hey i only missed one of the last drives of the year to work

ditch

Easy mistake to make but the fuse should have blown well before any smoke was let out of the wires
Best check out the reason for this as you could easily have a fire next time

quote:

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Originally posted by splitrivet
...
As for fuses a fuse is designed to carry current if a fire starts through a short or any other reason and the current doesnt rise above the fuses rating the fuse does nothing but let the current flow and lets the fire continue, a fuse does not protect against fire.
...Cheers,
Bob

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[/quote
While that's true for the device being driven, it's not for the cable - which looks to be the problem in this case.

A cable shouldn't catch fire unless it is carrying, much, more current that it's rating allows, and a fuse is there purely to protect the cable and MUST be less that than the cable rating (but more than the normal current for the driven devices).

So if the device normally takes 8A, the fuse should be 10A and the cable should be rated for 16.5A or more. Using 8.5A cable isn't good enough as there isn't enough headroom for the fuse to protect it.

A direct short will try to pull massive current (hundreds of amps) but the fuse should always blow before the cable gets hot enough to catch light. In my experience most problems are caused by adding stuff to a circuit and "fixing" the blowing fuse by putting in the next size up without considering that the cable might not be able to carry the higher current safely. [/quote


True in a perfect world but a fuse rated at say 10A doesnt blow at 10 A and can take up to 40% over its rating for several minutes before it blows by which time the device is toast the cable feeding it is cooked and the cables properties have changed.
Ive seen equipment cooked, cable at the equipment end frazzled and the fuse is intact.
Seeing as the vast majority building their cars are electrical newbies and are toting around several gallons of highly combustible material being extra vigilant aint a bad idea.
Cheers,
Bob

[Edited on 23/9/10 by splitrivet]

[Edited on 23/9/10 by splitrivet]

quote:

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Originally posted by splitrivet
True in a perfect world but a fuse rated at say 10A doesnt blow at 10 A and can take up to 40% over its rating for several minutes before it blows by which time the device is toast the cable feeding it is cooked and the cables properties have changed.

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quote:

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Ive seen equipment cooked, cable at the equipment end frazzled and the fuse is intact.
Seeing as the vast majority building their cars are electrical newbies and are toting around several gallons of highly combustible material being extra vigilant aint a bad idea.
Cheers,
Bob

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