I would forget about the ford wiring for the fan and do a rewire immediately, if not sooner, they were crap when new in this repsect and get worse with age, simple job to do under £5 diy.
There is a relay(timer) that operates the headlight wipers when the lights are on and the washer operated, pull this(don't know which one as car not here),or just unplug them.
tabetha