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MG MGF Technical - Front Fog switch Mk1 to Mk2 Conversion

The second MK2 front fog switch arrived today and I have the same problem as previously, so the switch must be internally configured differently.

The part number for the MK1 switch is YUG101470PMA
The part Number for the Mk2 switch is YUG1102590PMP

The MK1 switch is wired as follows and works perfectly:

Pin 1 Black with Grey Stripe
Pin 2 Black
Pin 3 Red with Black Stripe
Pin 4 Black
Pin 5 Red with Orange Stripe

When I connect the MK2 switch the Front fog lamps are on constantly no matter which way the switch is selected. Also the Dash illumination on the switch does not work and the On/Off illumination on the switch does not work.

This to me suggests that the switch is wired differently, however, both Mike Satur and Bill at MGF Centre say they do not have any problems when wiring these switches during conversions, yet other BBS members are also having the same problem as me.

So are the switches different, are the looms different, or is there a fault somewhere. I would appreciate someone with a MY2000 onwards car with Front fogs looking at the Switch loom wiring and letting me know the colour coding and number configuration on the connector. The connector can be accessed by removing the triangular footwell panel and gently pushing the switch out of its housing. The connector has numbers on it adjacent to each wire, I do suspect that I am going to have to reconfigure the wiring but why would Rover make this change, it is just so unnecessary and bloody frustrating.

Thank you in anticipation
Chris Catchpole

Can Mike and/or Bill confirm which way they wire the Mk2 switch (or have they already)?

If this helps any of the electrical gurus, I have taken the Mk2 switch apart and pushing the switch in seems to connect pins 1 and 4

I can take pics of the inside of the switch if anyone wants them.

There are also 2 LEDs inside, a yellow and white one, presumably these are the dash illumination and switch on/off illumination.

Pins 2 and 3 seem to be although i am not certain connected to a yellow LED and pins 3 and 4 to a white LED.

I am having great difficulty seperating the MK1 switch without causing damage.
Chris Catchpole

Mike and Bill both say they just connect the plug and it works, Bill is going to check the wiring for me but there does not seem to be any wiring diagrams.
Chris Catchpole

Pin 1 Black with Grey Stripe
Pin 2 Black
Pin 3 Red with Black Stripe
Pin 4 Black
Pin 5 Red with Orange Stripe

Black are the earths -so a little surprising that there are two?

Red with the black stripe is the instrument illumination live feed.

>> Pins 2 and 3 seem to be although i am not certain connected to a yellow LED <<

So this fits with the instrument illumination Chris

>> pins 3 and 4 to a white LED. <<

This is the put that doesn't make all that much sense to me - and this is probably why the instrument illumination doesn't work, as the instrument live feed will presumably go straight to ground? It certainly wouldn't help with switch-on illumination!

I *suspect* that pin 3 should be ground (black) and pin 2 be red/black.... but we need a little more information...

What sizes are the red/orange and black/grey wires? I assume that one will be one of the relay wires, and the other a switched live feed from the dipped beam headlamp circuit.

Take a multimeter or light bulb, and see which one goes live when the lights are on.
Rob Bell

I have posted pictures of the connector and switch which is flipped open on

Feel free to browse
Chris Catchpole

In the photo the Balck with grey stripe wire is Pin 1 and the switch is open Pin 5 on the left, pin 3 showing in the middle, Pin 1 on the right.
Chris Catchpole

Ah. There's a problem Chris. I am not sure that the 'lines' on that circuit board properly correspond to the pin positions on the plug? It might do, but I am not totally confident of that.

If you have access to a circuit tester, at least then you'll be able to tell which of those copper lines corresponds to which pin at the plug.

Having a look at the rear fog wiring diagram, the red/yellow wire is the one that provides the power for the rear fog lamps: it goes live when the MFU detects that the dipped lights are on. There is no reason to think that this would be any different for the front lamps.

So we can now identify the R/B, B, R/Y wires on your loom. That leaves the black/slate grey (B/S) wire. This, I assume, will be the one that takes that signal to the fogs. What colour are these wires actually at the lamps? Need to look at mine, but haven't had a chance recently!
Rob Bell

The wires at the lamps are red with yellow stripe and Black on both sides
Chris Catchpole

On the Switch

Pin 2 goes to right hand side of Yellow LED
Pin 3 goes to left hand side of Yellow LED and right hand side of White LED
Pin 4 goes to left hand side of white LED
Chris Catchpole

The wire at the lamps are RY??? Okay, now I am confused.

What happens to RY and BS when you turn on the side lights - one should go live, the other goes to ground, irrespective of lighting status.

From the point of view of the internal illumination of the switch - I'm feeling more confident that PIN3 is a common ground. As these are LEDs, they'll only work if the polarity is correct - so this is easy to check if this is indeed the case.

Just to clarify Chris: is the white LED the 'switch on' reporter, and is the yellow LED the switch illumination?

If I'm right, then Pin2 should be RB. However, it looks to me from those pictures that Pin1 is also in line with Pin2? If this is the case, then it would make more sense if the yellow LED were the reporter not illumination! Argh! This is doing my head in!!!
Rob Bell

The white LED is the On/Off reporter illumination and the Yellow is the switch illuminator when the side lamps are on.

In the connector Pins 1 + 4 and 1 + 2 give a 12 V reading when the sidelamps are switched on which means B/G is live and B is Earth. The Fog lamp switch appears to activate pins 1 + 4 when in the on position, which makes sense.

That leaves R/B and R/Y pins 3 and 5. Do you think these two could be reversed.

Chris Catchpole

The answer to that is no, just swapped 3 and 5 over and the fault is still the same, fogs on constantly, no switch LED illumination.

I have also had a look at a TF Fog lamp and it has Red and Black wires in the lamp as opposed to my Red/Yellow and Black so the looms are different, god only knows why.

Chris Catchpole

Can't someone please pop a front fog switch out for me and check the wiring, its driving me mad.
Chris Catchpole

Swapped wires for pin 2 and 3 and blew a fuse.

Pins 1 and 4 are Live and Earth for on/off and the fogs work with the Side light on/off with those connected.

So by connecting those two only I now have working fog lamps. Which leaves me with pins 2,3 & 5 which must operate the illumination and reporter.

Swapping 2 and 3 blew the fuse.

Swapping 3 and 5 blew the fuse.

That only leaves 2 and 5.

The Red Black wire is 12v Live with the sidelights on, the black and red/yellow are to ground.

With the switch in the on position I get good resistance across pins 1 & 4 and 3 & 4, if I connect Black/grey to Pin 1, Red/Black to pin 3 and Black to pin 4. I get 12v from 1 & 4 and 3 & 4 in the off position however,I only get 12v from 3&4 in the on position and I have discovered after connecting red/black to pin 3, pin 5 gives 12v output when the side lights are on, hence the blowing of the fuse when i connected it to earth. So pins 3 and 5 are internally connected within the switch.

Would it therefore make sense for 3 & 5 to be grounded, making pin 2 live.

Both Red/Black and Black /Grey appear to be live when the side lights are on.

Time for a break and i am going to take out my frustration on an old shed roof which i am going to demolish and replace.

Be back later, with hopefully some ideas from you guys.
Chris Catchpole

What's happening with PIN5 Chris?

RB is definitely instrument illumination - comes on with side light/ Dipped Beam (DB)/ Main Beam (MB)

The Black/Slate (BS) wire is presumably the switched 'live' from the MFU - and will only go live if DB is on, but should be dead if SL or MB are on.

If the front fogs are like the rear, then RY will be switched from the relay in the MFU - and thus will only be live when BS is live.

If think we're making progress Chris!

I've got my original switch here, and I've been seeing how the switch operates with a circuit tester.

With the switch open, we have pins 2 and 3 making a circuit, as do pins 4 and 5.

With the switch latched, we have pins 2 and 3, pins 4 and 5 making a circuit, as before, but now joined by pins 1 and 4 and pins 1 and 5.

From this, one can see that pins 2 and 3 are the instrument illumination (B and RB respectively). Pins 4 and 5 are the reporter lamp (B and RY respectively).

The switch allows pin 1 and 4 to make a circuit, so sends 1 to ground, powering the relay so that Pin5 comes live and they both go to ground through pin 4.

So my question to you Chris, is how your MY2000 switch compares to this logic sequence?
Rob Bell

Chris - this is how I think that the front fog lamp circuit is wired up on the MGF:

I think that you are going to need to check your MY2000 switch to see how the gating function works: I wonder if the pin order has been reversed?
Rob Bell

Ok my connector is wired differently to the diagram, unless the diagram is numbered incorrectly wires 2 and 3 are transposed.

Regardless of side lights or dipped beam selected the output is the same, wires 1+2, 1+4 and 1+5 all give a 12v output before connecting to the switch.

On my connector: Wire 1 BS
Wire 2 B
Wire 3 RB
Wire 4 B
Wire 5 RY

The Mk1 switch works perfectly in this configuration.

The New Mk2 switch has no resistance across any pins in the Off position, no circuit.

In the On position:

Pins 1 + 4 have full resistance, make circuit
Pins 1 + 5 have full resistance, make circuit
Pins 4 + 5 have full resistance, make circuit
Pins 1 + 3 have slight resistance with reverse polarity pin 1 -ve pin 3 +ve
Pins 1 + 5 have slight resistance with reverse polarity Pin 1 -ve pin 5 +ve
Pins 3 + 4 have slight resistance both ways
Pins 3 + 5 have full resistance, make circuit

I would really appreciate someone popping out their Mk2 front fog lamp switch to check the wiring configuration , it is only a 5 min job and you could save Rob and I a lot of headaches.


Chris Catchpole

>> unless the diagram is numbered incorrectly wires 2 and 3 are transposed. <<

Oops. You're right Chris. Error on my part. I've now corrected the diagram (same addess) so that the colour codes for the respective pins are correct.

What does 'slight' versus 'full' resistance mean Chris? Surely whether there is a circuit or not is more important?

I'd definitely agree that if we could see an MY2000 MGF or TF fog lamp loom that'd be enormously helpful.

Rob Bell

When I set the metre to Ohms, the needle went fully across, which I took to be a circuit. However on some occassions the needle only moved slightly, maybe 5 mm or so, but it definately moved so there was something there. i don't know what that means though.

I am going abroad for a week now, work I'm afraid and no play, so I will watch for any further help when I return next Saturday.

Thanks Rob,

come on you mgtf/MY2000 guys, get outside and check those Front Fog connectors, you know you want to and we can then put this info on the Websites to help others.
Chris Catchpole

This thread was discussed between 12/02/2004 and 16/02/2004

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