16 replies to this topic

[THE ANORAK]

anyone else have trouble with the internals of their headlight switch melting ???? mine went again today (forth time in five years) but i want to know why.

basically the plastic around the pins is getting soft and the pins are sinking and breaking the connection.

my spotlights are wired through a genuine rover loom and relay and they haven't been on the car when its happened before.

could it be the halogen headlight bulbs ?????

would a metal switch solve the problem of just relocate the heat to something else ????

[FartinMartin]

Dodgy connections behind the grill pannel for the lights will make the bulbs draw more current

Its 99% of the time these that cause those sorts of problems

[ANON]

have you got a relay wired in or are the lights just switched ??

[Dan]

Dodgy connections behind the grill pannel for the lights will make the bulbs draw more current

That's just the tip of the iceberg. Essentially the switch isn't adequately rated. The plastic rocker switches used in Minis are rated at 16A continuous. The standard lighting, when new and with sealed beam lamps or tungsten bulbs draws around 14.7A. That doesn't leave much breathing room. The halogens do draw a little more power and its often these that are the final straw and cause the switch to melt but the real problem is corrosion. Corrosion in all the joints of the wiring harness, seen as green or white deposits. This has a much higher resistance than the harness should have and as such the joints of the harness each become a load on the circuit. Sometimes the rot spreads up the wires inside the insulation too. Clean all the joins and the problem would go away, temporarily. With only 1.-very-little amps available to play with before the switch is overloaded it doesn't take a lot of corrosion to start the melting. The best solution is to remove the largest load from the circuit, namely the headlamps. Shift the dipped and main beams onto relays and all the melting will stop.

Why do you think halogen lamps didn't become standard until the main lighting switch was replaced with a better switch in the stalk?

[satvinder]

quick question to help me on my fogs. on the outside of the switch. there are small flat metal plates. one on to and one on the bottom, what are these??? are they earths by any chance?

[THE ANORAK]

thanks Dan

any diagrams to show how to wire the relays in ???

would a higher rated switch be another way to solve the problem ???

[M44K TS]

http://www.ado13.com...s/relaywire.jpg

That's helped me out god knows how many times

[THE ANORAK]

found a 25amp / 12 volt toggle switch on line

[Dan]

small flat metal plates. one on to and one on the bottom

Assuming you don't mean the spade connectors for the switch lighting they are just springs that hold it into the panel.

Anorak, yes a higher rated switch would also solve it but you won't find one that fits straight in and it'll be a bit of a lashup.

Make a harness to mount on the front panel, couple of relays and some fuses. Take feeds from the solenoid. Remove the inputs into each of the dipped and main bullet blocks and use them to trigger the relays. I did a very comprehensive writeup on this once before.

[M44K TS]

I think i'm right in saying that if you fit relays to the dipped and main beam, then basically, all the switch is powering is the relay there won't need to be any need for a higher amp rated switch as the majority of the current is going through the relay.

[THE ANORAK]

OK, thanks everyone

may have to go for the cheapest option at the moment (£5 for a 25amp switch) and mount it somewhere else till i can sort it properly

Edited by THE ANORAK, 21 January 2009 - 05:12 PM.

[Bungle]

i can talk for through the relay route but can't draw a picture on the computer to post up

you use the live from the switch that used to go to the head lights as a trigger to turn on the relay

you then power the relay via a fuse from the solenoid

now run a wire from the relay to the head lights

and one more from the relay to earth

ummmm might do mine while the engine is out and i'm tidying up

[dklawson]

Dan and M44K _TS are both correct and adding the relays will remove major current demands from the toggle or rocker switch.

The JPG link provided above is nice and it shows the standard Bosch/ISO relay pin terminals. I have such a relay panel on my Mini and I'll be adding it to my Spitfire when I get to that part of its restoration. My panel uses two relays, one for the high beams, one for low beams.

In addition to other write ups about this I'd like to direct you to the Advance Auto Wiring web site:
http://www.advanceautowire.com/
Click the link on the left side of the screen for their headlight relay kit. Scroll down past the picture of the kit and you'll see they have kindly provided a schematic for a dual relay system. As with the link provide earlier, the system uses Bosch/ISO relays and all the terminals and standard Lucas wire color codes are referenced on the schematic.

[M44K TS]

i can talk for through the relay route but can't draw a picture on the computer to post up

you use the live from the switch that used to go to the head lights as a trigger to turn on the relay

you then power the relay via a fuse from the solenoid

now run a wire from the relay to the head lights

and one more from the relay to earth

ummmm might do mine while the engine is out and i'm tidying up

Is that what you mean?

[THE ANORAK]

ha ha, cheers guys, yes i think i understand the relay thing now, when i was fitting my rover spotlights and loom i had one of those "aha, so that's how its done moments". its quite simple really once you understand how its done.

i just wanted to confirm which wires go where etc.

the thing is, a new switch is gonna cost £12 plus relays and fuses and wire and connetctors etc. etc.

well either me or the wife needs to use it straight away (in the dark) so a quick fix is going to be a cheap non standard switch

plus the insulation on the origional wires is showing signs of heat damage as well so im going to have cut them anyway.

i will sort it properly, eventually