Rheostat - dash light dimmer

[Tasmindevil]

Couple of questions, which vehicle is the dimmer switch aka rheostat off, not a ford, landrover, sd1 or tr7 so a bit confused, also mine has three wires, main feed, one to the dash lights but no idea what the third one is for?
Cheers
Hamish

[Wedg1e]

SD1.
As it's a rheostat, essentially one side is 12V, one side is earth and the other is the 'tap' to feed the lamps.

They are prone to fail if you leave it set just below fully-bright. Either turn it on full or go for about 50% and it should be fine but the resistive track isn't rated high enough to dissipate the heat created by having it just below full brightness.

[Tasmindevil]

Thanks Wedg1e, defo not a SD1 switch but could be an aftermarket, that said both my 400se had the same switch, it's black, 1" dia and is a push fit all plastic and its toast by the way.
my wire colours dual coloured red/white - live, red/black - lights, red/green - errrrrr

[Wedg1e]

Ah sorry, failed to read the bit where you said NOT SD1...! The later cars used the Granada Mk3 column, maybe it was from that (I see you said not Ford but didn't know if you knew about the later column)...
otherwise maybe it's some aftermarket part not necessarily intended for a car?

[ukdj]

had one fitting that description in a peugeot 205 gti, no idea if it's the "correct" part but may do the job.

[Tasmindevil]

So found the switch, its from a TVR S1 so basically on or off and not a rheostat after all, top picture http://www.pistonheads.com/Gassing/topic.asp?h=0&a...
Thanks for your replies

[adam quantrill]

Looks like a 3-position switch then like on the 400SE - on, dim, bright?

[Tasmindevil]

adam quantrill said:

Looks like a 3-position switch then like on the 400SE - on, dim, bright?

Yes I broke mine thinking it was a rheostat and after much searching I discovered its the three position one, I believe it comes out of a Vauxhall, Nova or Astra from mid 80's but like rocking horse doo doo so I will probably go with the mod recommended in the S forum post.

[adam quantrill]

Is it actually broken or maybe the wiring or dimmer resistor is broke?

[Hamish400]

On my car the 3position switch is on, dim, or off. When my 3position switch was not working to dim the dash lights it was due to failure of the series resistors in the "dim" position. These were a pair of ignition ballast resistors located in the engine bay lhs. The resistors were the type made of a ceramic block with a wire and spade type wiring connections.

Reds
Hamish

[Hamish400]

On my car the 3position switch is on, dim, or off. When my 3position switch was not working to dim the dash lights it was due to failure of the series resistors in the "dim" position. These were a pair of ignition ballast resistors located in the engine bay lhs. The resistors were the type made of a ceramic block with a wire and spade type wiring connections.

Reds
Hamish

Edited by Hamish400 on Monday 27th April 21:21

[Tasmindevil]

Cheers Adam & Hamish, I took the dash out to check and solder the wires getting rid of some crimp connectors plus install some LEDs instead of the Fibre optic lights on the switches and alas that is when the switch fell apart in my hands, just age but I might be able to get another. Thanks for the heads up in the resistors, I know them well but never knew they were for the dimmer.
Thanks again
Cheers
Hamish