There's two possibilities. There's a bad ground on the motor assembly or a defective park switch inside the gear housing.
The assembly is mounted on rubber bushings to isolate vibration. A brass ground strap attaches to the mounting plate and goes under one of the mounting bolt heads. The strap burns under the bolt head. Running a new ground wire will solve that. Typically the wipers will also stop running randomly while on low or high, not just on delay mode. You can verify this by measuring the voltage on the motor mounting plate. There should never be any voltage there when the wipers are turned on and supposed to be running. If you do find voltage there, add the new ground wire.
The park switch keeps the motor running only when your control switch is turned off and the wipers haven't reached the park position. If the contacts are burned or pitted, the motor may only run each time the delay relay clicks on for a fraction of a second. Measure the voltages on the wires on the motor connector when the ignition switch is turned on and the wiper switch is turned off. One wire must have voltage to feed that park switch. If it's missing, look for a break in that wire. The motor will still run in low and high because different wires feed those modes.
Friday, September 16th, 2011 AT 11:31 PM