Dim-Dip Lights fault finding on a mk2 16v

[mk2rolf16v]

Does anyone have experience in fault diagnosis for the dim-dip function for headlights?..... I have a 1990 gti 16valve, and when turning sidelights on, the dim dip feature should switch on. Ive tried things like checking all connections, using a different light switch and replacing the headlight bulbs..... but to no success. I've tried probing around with a multimeter, I'm thinking its most likely the resistor coil, but dont know how to test....
any help would be much appreciated.

[dubber36]

The dim-dip resistor is a packet of polo sized tube that lives on the inner wing behind one of the headlights (can't remember which one) Many of them pack up and cause other problems with the lights so get removed.

[The Mighty Elvi]

The dim-dip resistor is a packet of polo sized tube that lives on the inner wing behind one of the headlights (can't remember which one) Many of them pack up and cause other problems with the lights so get removed.

Off side.

[rubjonny]

there are also some yellow wires behind the fusebox for it, 2 a 2 pin or 2 single pin plugs.  the resistor wires can rub thru and short out on the chassis leg, if that happens it sets fire to the headlight loom. i always remove them for this reason as it doesn't really perform any useful task. who needs an extra light level setting between sidelights and dipped beams anyway