electrics advice needed

Hi, defenately on the last stages of the rebuild.

1988 csw 110

When I got her, the heated rear screen didn't work and I thought I'd wait until the rebuild to fix the problem.

Power comes from the ignition to the switch - ok

Two wires leave the switch - one to the clocks and one to the relay - both ok

The relay has a live from the ignition - ok

The live from the relay doesn't work - tried another relay and still doesn't work. I ran a live to the relay out to test the continuity of the circuit to the screen via the fuse - that was ok.

The earth from the relay goes to a diode - ok

Diode to big yellow voltage switch - ok

However, the live (small brown wire) to the voltage switch has nothing. The earth on the voltage switch is ok.

1. Could the voltage switch be f*$ked?

If I connect the relay earth straight to an earth rather than the diode the circuit is fine.

2. Why do you need the big yellow voltage switch.

3. If I didn't use the big yellow voltage switch how does the system turn its self off or should it not do that on a 1988 model?

All comments welcome (although I'll regret saying that on this forum!!!!)

:welcome2:

After a lot of messing:

The brown wire to the yellow sensative switch comes indirctly from the alternator and is designed only to let the system work when the engine is running.

One of the bushes in the alternator was stuck back due to a build up of crap.

That's sorted and now I've isolated the problem as the yellow sensative switch.