troopy wipers come on without touching lever.

Electric wiper motor units of that age and earlier had a simple electrical contact that was operated by the gear wheel that controlled the wiper arms. There was a cam on that gear wheel that opened the contact when the wheel reached the park position in its rotation. That contact was wired directly to the battery, it would supply 12 C to the wiper motor if the wipers were not in their parked position. That is how the wipers self parked after you switched them off. Your wipers may or may not employ this method of self parking.

If your wipers work this way, check that the spring lever that has the contact on its end has not malfunctioned somehow. If there does not appear to be a sufficient gap between the contacts, do some adjustment to that lever.

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Bob, it could be a faulty switch in the steering wheel hub but is more likely a wire shorting to the bodywork. The wipers operate by having 12v+ supplied to the wiper motor from the ignition source via the fuse then the circuit is completed through the steering hub switch to earth. If one of the wires from the motor to the switch rubs through its insulation and contacts earth then that will bypass the switch and operate the motor.
Examine your wiring loom from the wiper motor to the switch looking for wear. A very likely place is where the loom enters the steering column. If you find a wear point, wrap it well with insulation tape and try to reposition it away from the earth metal.

If it does happen to be the steering hub switch then they are somewhat difficult to access and tricky to repair. You may need help from an auto electrician.

EDIT: I agree with Peter's suggestion above. Can also be tricky fiddling within the motor. But if your mechanic has a spare it could be tried. Then, if the fault is still present it suggests the wiring short That I mentioned.

We've had several troopies over the years and on extremely corrugated roads it has happened on all of them, the actual wiper switch/arm vibrated so much it actually dropped down and activated the wipers.
Sometimes it was just enough to make them work and park and others they just kept going until you flicked the arm back up.
Doesn't sound like that is the case with your troopy, if its not a wire shorting out I'd be inspecting the switching in the actual wiper motor as the contacts in there could be shorting.

My 60 series used to give a random one wipe for years and I finally accepted it as its eccentricity. Gave passengers something to talk about.
Graham.

Haven't looked at the circuit but if it has intermittent function then it could be either the electronics that make it work or the relay if it has one. Could try removing the wiper relay if there is one and see if that stops the issue. If it does then a replacement could be a chepa fix if its not the electronics if they are seperate.