I've just lost and regained my connection to the website so this might come to you twice - sorry if it does. Anyway, I'm confused. Having measured 4.5v at the light switch, I checked the voltage at the ammeter. Where three wires leave the ammeter, I got 4.5v. Aha, I thought, if there are about 6v where the single wire enters the ammeter, then the problem is at the ammeter. But the reading was 0. How can that be? Phil.