Just been looking into putting a couple of relays in for the headlight... But am trying to establish whats the best route to go... short and simple or adding some complexity into it...

Is the diagram I have drawn potentially going to be too slow in switching?

Just to clarify when I say old loom I mean the original conection to the headlamp...

My short and simple diagram:...

I have what you call the simple one and I works just fine.
The bosch relays I used have a switching time of 10 - 12 milliseconds so I really don't think you will be concious of any lag.

short and simple works just fine twincarb .....and if you need you can go back to the original purdy easy ...(not that you would want to ) we gotta look after those poor old switches and wires .

This is how I did mine:
http://k100rt.aforumfree.com/t1184-converting-k100rs-to-k100rt#6841
It echos your simpler design. Relay switching time has never been a problem and it has been working great for years now.

thanks for the replys, Rob having had a quick read of your posts, so i can see CF reason for the full circuit, however I cant see anything going wrong with the simple method...

Twincarb,

The more complex solution has the same relay parts count than the simpler one but the added diodes prevent damage should the circuit be plugged in improperly. That is a mute point if you plan on making the circuit part of the wiring harness. The simpler circuit functions equally well, is easier to wire up and test and probably has slightly better reliability having a lower component count. I think you'll be happy with either one.