Does this description sound accurate to you?

[JohnPatrick]

Hello, I've got a new dip switch in my parts box, and it seems to have come from one of the usual sources. However, it's stamped with "10A 250v, ac only" and has only three terminals, unlike the previous one and the wiring loom, which had four. Does this description sound accurate to you?

[cactusman]

Probably. The original probably had four terminals but two were commoned. The replacements will just have three terminals as the switch is just a single pole changeover and probably sourced from an electronic components supplier...and will be rated at 10 amps/250 volts max. Just connect blue to the centre terminal, blue/green to one outer and both blue/yellow to the other outer terminal. Blue is supply in from the light switch. Blue/green is dipped out to the dipped lights fuse and blue/yellows are head beam out to the head beam fuse and also to the head beam flash on the indicator stalk (this might be blue/white?) I'm assuming you have a series 1 3.8 or 4.2 by the way. S2 and S3 cars are probably different...