Hi Nige, what I ended up doing was completely stripping two switches, the original broken switch, and the dash light switch, so I could see what was wrong with the original switch and fix it. I managed to fix the original switch, and yes, they appear to be exactly the same.
And you are correct, both are just momentary contact switches. What confuses me further is that all the relays are on/off relays, none are latching relays: the type that hold the state when the switching current is removed... (I opened the relays up to have a look inside them).
So it makes me wonder if, either someones replaced the switch in the past with the wrong type, replaced the relay with the wrong type, or there's some fault in the wiring.
The other thing I dont really get is: the full beams, rear fogs and heater fan all stop if you pull a certain relay. However this relay is just a single switching relay as described above(not latching), and it only switches one current.. so How does it switch 3 different functions on the car!? Maybe some of these systems work with multiple relays?
Anyway, I've got a simple on off switch, so am going to experiment with joining wires.. if that works, install my switch somewhere discreet that dosen't involve making holes in the dash!
Yep it can be very confusing, even looking at the fuse/relay list doesn't really make a lot of sense and I'm a certified Electronics Tech Eng.
Or maybe at my age the brain is wearing out !
Could be that it's not an obvious latching relay in the sense that it's not mechanical and it uses an extra set of contacts to provide the " Hold On " volts. I have a feeling that you know what I mean.
Again a chain of relays doesn't sound too far fetched either.
I'm with you on the current plan to just to replace with a normal switch. Do take care though, you don't want to be permanently energizing some circuits that are not designed to be on all the time, I would take a lot of time checking things. It's always best to repair the original fault if you can rather than doing workarounds but I know this can be very difficult at times.
I hate car electrics, seem to be illogical in may ways. I fixed my friends Escort Airbag light which was on permanently by pulling the fuse as indicated in the book. The book said that it only supplied the warning light. When he run out of petrol in town a few days later realized that it also supplied the fuel gauge which on fuse removal had frozen at Third full !
You get the idea. Good luck and let us know what happens, it's nice to try and remember fixes like this.