[Ian21401]

Thanks Dave.
I didn’t hint at what my suspicions were as I didn’t want to influence any possible replies.
The fact that the motor appears to run as it should when disconnected from the harness and jumped from the battery seems to indicate that the motor is ok and the fault is elsewhere, ie, the switch. I managed to remove the switch and open it up before I did anything else. It was possible to gently prise the plastic switch casing apart to expose the contacts. They were a little dirty so I gently cleaned them up and sprayed them with contact cleaner. Three of the fixed contacts which have other contacts sliding on them do appear to be rather worn, which is not surprising after 27 years of use. A comment on “brickboard” suggests applying solder to fill the worn areas then smooth it down but I don’t think that I have sufficient expertise to do that. I’d probably melt the plastic bits.
I’ll double check the motor action whilst I have it on the bench then do as you suggest and check again.
I’m awaiting delivery of some butyl sealing strip to re-seal the air intake cover and secure the metal mesh before refitting the scuttle panel so I’ll trawl around for a replacement switch which will have to be for an estate as needs to have the rear wash/wipe wiring.