I am ok with old school electrics but might be losing the plot with my FL2 so here goes with a question for the electrickery gurus ....

I need to find a 12v feed from either headlight or sidelight. It is basically a trigger for a relay that turns off my DRLs when the lights are on. For some reason it doesn't seem to work and even if I connect it directly to the headlight feed at the loom plug it refuses to work (connecting to the battery however, works ok) - is this the canbus system being a bit clever or am I missing something? Cheers,
Raz
FL1 TD4 GS Auto 2001 Silver
FL2 TD4 Auto 2007 Black
FL2 XS SD4 Auto 2012 Fuji White

Are you sure you've found the right wires? No offense intended, but...

Headlights and sidelights are driven by small FET's (field effect transistors).
Maybe your relay has a too small winding resistance for the FET to cope.
Or maybe its inductive nature is what upsets the FETs, even if the ones used on FL2 are designed to cope with inductive loads.

If the relay has an internal diode in parallel with its winding, then be carefull how you connect the relay in the circuit, because if you connect it the wrong way it shortens the circuit. Try reversing the way you connect the relay winding to the circuit. Again, this is true only if you have a diode in parallel with the relay winding. And many times the auto relays have one diode inside by construction... Generally on an automotive relay, the winding is between 85 and 86 terminal markings. And the 85 is the one connected to (or towards) the ground and 86 to (or towards) the +12V signal.
See here: http://www.type2.com/library/identifi/bosterm.htm

Anytime I needed to connect to a FET driven signal in order to command a relay, I've used a small transistor to drive the relay. In this way I've drawn only a small current from the line.

Thanks for your detailed reply Alex

Basically I have bought a ready wired relay on eBay (very lazy I know). It works fine when connected to a battery terminal so you may be right - I might not be connecting to the right wires!

After removing the L/H headlight plug, I poked a test wire into the sidelight feed (at least I think it is) and I get 12V on my multimeter with the lights switched on - trouble is I get 9v when they are switched off ...... very confusing. I cant remember the actual wire colour but it may have been GR/OR. Does the circuit behave differently when not under load (ie with the headlight disconnected? Cheers,
Raz
FL1 TD4 GS Auto 2001 Silver
FL2 TD4 Auto 2007 Black
FL2 XS SD4 Auto 2012 Fuji White

Yes, green-orange, pin 2 is the L/H position (sidelight) wire. In fact pin 2 is the sidelight pin in both L and R connectors. Only that on the R/H its color is brown-yellow.
Yes, the pin has a residual voltage on it because of the FET's (in fact it's a small integrated circuit, BTS443) open circuit detection.
Try to take the signal from that wire with the lamp connected, not with its connector "in the air". Pierce the wire with a small pin.

Thanks Alex - exactly what I needed to know  Cheers,
Raz
FL1 TD4 GS Auto 2001 Silver
FL2 TD4 Auto 2007 Black
FL2 XS SD4 Auto 2012 Fuji White

On the topic of FET's, does anybody know if they are programmed according to the equipment fitted to a particular model (S, SE, HSE, etc)?
I want to fit footwell lights, but am not sure if the controlling FET on my S model (South African spec) will be able to handle it - ie, was it perhaps programmed NOT to allow these lights? Snorkie
Pretoria
South Africa