Smoking Light Switch

[windysurfer]

Whilst on my way to work this morning my headlight switch began to smoke and the dash lights went out.

Took the dasy out and removed switch and at first glance it looks like its the wheel bit (tech term!!) which was smoking.

Now I did replace my dashlight bulbs with LED's about 8 months ago so this whell no longer has any effect so I'm not sure why it's started to smoke.

Could really do with finding out why this has happened as my car is off the road and I need to use the van for work and theres a good change it will be going dark on the way home

Any ideas what to look for when I pop out on my break??

cheers

Gaz

[VWlewis]

I would check the wiring between the switch and the lights - not easy of course but the smoking suggests there is a short to earth causing the switch to overheat as large currents flow through it.

Perhaps the first place to look is around the fusebox and then behind the headlamps for any wires with melted insulation.

Have you done any work on the headlamp circuit - e.g. fitted relays? This would also be an area to check in my experience!

Hope this helps... let us know how you get on.

[windysurfer]

I've not altered anything.

The wires behind the dash look OK.
I've now had a proper look at the switch and the bit which has melted is the windings which control the amount of current for the dash lights.
I've also got the dash sat on my desk should I need to check anything on there.

Do you thing the problem lies before the current actually gets to the dash lights or could it be one of the dash LED's shorting out??

cheers

Gaz

[VWlewis]

Ahhh .. so the circuit that is causing the problem is not the headlamp one but the instrument panel lighting. Have the LED's got a resistor fitted - see here for guidance on resistors http://www.kpsec.freeuk.com/components/led.htm

Sound like something is shorting in the LED circuits or no resistor is fitted.

Hope this helps.

[windysurfer]

The LED's have been fitted about 10 months but I don't think there are any resistors fitted.

The coil type thing has melted so the dash light circuit has been broken and the dash lights went out but the switch was still smoking.

I would have thought that if the circuit was broken the smoking would stop?

Or would that make it smoke even more?

cheers

Gaz

[VWlewis]

OK Gaz - I would isolate the dimming switch, bypassing it and just wire the instrument panel lights directly then. Dimmer switches are known to breakdown as they get older. You might want to measure the current draw when you connect up the lights (if you have a multimeter) - I would not suggest you should use resistors with LED's or else the LED's will burn out eventually too.

... to be continued!

[Mr Bean]

Whilst on my way to work this morning my headlight switch began to smoke and the dash lights went out.
Any ideas what to look for when I pop out on my break??

cheers

Gaz

Hopefully a short circuit would blow a fuse rather than setting your dashboard on fire! I did have this this problem on my Bedford CF and found it to be heating due to electrical resistance (poor switch contact) in the parts of the switch which make the connection. Eliminate this posibility by removing both headlight bulbs and the leds in some logical sequence. I had to dismantle the switch and refurbish the contacts. It may however be the headlight current is switched via a relay which could complicate things. Even dipped headlights draw significant current. Hope this helps
Ken

[Red Westie]

The dimmer switch is a variable resistor, the amount of resistance depends on where the contact terminal locates itself on these windings.
The contacts can become tarnished over time, this creates a higher resistance and therefore generates heat.
It might be that there is nothing wrong with the wiring, just that through age the resistor contacts have weakened and tarnished and then overheated the switch.
Martin

[windysurfer]

I've got a new switch coming from Syncrospares so I've pulled my old one in pieces and removed the variable resistor so hopefully when I plug it bak in my lights will work without my dash lights.

I've also checked the actual circuit board on the back of the dash and that looks OK.

I've got a multimeter in the van but don't know where to stick it or what to test.

I don't want to put another switch in before knowing what caused this one to melt.

Hopefully it was only the switch overheating

cheers

Gaz

[windysurfer]

Right , just plugged everything back in minus the resistor windings and my headlight work ok with no burning smells.

So does this tell me it was the switch?

I did have a look aound the fuse box and there was no sign of any charred wires.

Can I just not by pass the dimmer altogether?

If so how?

cheers

Gaz

[Mr Bean]

Right , just plugged everything back in minus the resistor windings and my headlight work ok with no burning smells.So does this tell me it was the switch?I did have a look aound the fuse box and there was no sign of any charred wires.Can I just not by pass the dimmer altogether?If so how?cheersGaz

Well I am tempted suggest that you probe around with a multimeter wearing your Mrs Marples hat so you can find the wires/terminals with the variable resistance between them. I would also suggest that when you decide which ones you short them out with an in-line fuse of a suitable value. This way if you got it wrong you may avoid blowing it up. However this all depends upon your ratio of knowledge and ignorance. You can operate at any ratio but tending towards the knowledgable always gives best results.
Cheers
Ken

[windysurfer]

I've got somebody with a bit of electriacl knowledge to have a look in my Haynes manual and decipher the wiring diagram.(p12.33- haynes 1982-1990 petrol)

I'm going to connect 58 and 58b together using a fuse. This should bypass the resistor and just put my dash light on full all the time.

What size fuse should I use?

[tonytech]

It sounds like your replacement LEDs may have failed, drawing too much current through the resistor. The dash lights shouldnt draw more than 1 amp, so replace the resistor with a 2 amp fuse and see what happens.

T