UK fog switch electrical problem

[jon_st205]

Hi all,

Retro-fitting a UK fog switch into an import to keep it OEM-looking. All pretty straightforward you would think! It all works fine but the telltale illumination on the switch itself is staying constantly lit, rather than just coming on when the button is depressed. The switch works in terms of turning on and off the output to the fog bulb, just that it's constantly lit - no good for MOT I'd imagine.

The switch itself just has 3 pins, 12v output (red/white, to fog bulb) , ground, and two red/green 12v inputs going to the same pin. If I apply 12v to either of these inputs I get the same result (constantly lit but output working fine).

Any insight to what I'm doing wrong? Is there a fault with the fog switch?

Cheers,
Jon

[knocker]

Hi I am in the process of planning to wire my fog light as mine is also an import, you mention the OEM switch can you confirm which one it is?

[jon_st205]

Just the UK standard one, fits instead of the blank - visible top of my pic. You'll need it with a 'pigtail' loom piece.

In theory it's dead easy, just wonder what I've done wrong....

[kaiowas]

From the wiring diagram I'm looking at, I think you have the switch wired the wrong way around. r/w should be the 12v feed (which is via a relay on the oem installation) and the r/g is the switched feed to the foglight (the telltale light is also connected to the r/g side of the switch which is why you have it always lit)

[jon_st205]

Brill, thanks. I'll swap 'em over.

[jimi]

From the wiring diagram I'm looking at, I think you have the switch wired the wrong way around. r/w should be the 12v feed (which is via a relay on the oem installation) and the r/g is the switched feed to the foglight (the telltale light is also connected to the r/g side of the switch which is why you have it always lit)

The only other thing I'd say is that according to the diagrams you should have
red/white - 12v supply
red/green - 12v to foglight (also linked internally in the switch to the telltale lamp)
white/black - ground for the telltale

[jon_st205]

Thanks again, all sorted. In the process I found my wiring notes from when I tested it on the workbench, and I had written them the correct way around and then somehow soldered them the wrong way around....so dunno where my head was at that day!

Oh well, happy days and one more job finally ticked off.

Jon

[jimi]

Glad you got it sorted.