There is only a wiper relay if there is an intermittent wipe facility fitted. On earlier 90/110s you have 2 speeds and if you push the switch down it wipes once and stops.Auxilliary feed goes to the wiper switch and when you select the speed you want supplies the power to the wiper motor, the other wires are for the park circuit and the earth. Unplug the 5 pin plug at the motor and, with the ign on, use a test lamp to probe the appropriate pins in the wiper motor plug corresponding to the speed selected at the switch. If the lamp lights you have power coming from the switch to the motor and the fault lies with the motor, if not move back to the wiper switch and check that there is power coming from the switch. If there's no power it's the switch at fault and if there is power coming from the switch but not reaching the motor check the wires between the switch and the motor plug for continuity in case there is a break in one of them. Always check you have a good earth connection between the motor plug and the ring terminal that screws to the bulkhead at the motor.
all the best,
Stevie.
