Well I got the switch out, so that's further than I've got before. It all seems ok & I now think that the looseness of the switch is not the problem, I have simulated the action on the plunger using a screwdriver through the hole & it is proving that the lever will be operating the plunger ok & the connections as far as I can see are clean & in good condition. I've notched the ASV lever up a bit to give a little more movement just in case it wasn't quite allowing the plunger to release. If fault still exists I'll have to think again, but at least now I know the switch is good.