'99 Corolla Rear Wiper Won't Turn Off

[perdaniel]

My mother has a 1999 Corolla liftback, she has a problem with its rear wiper which sometimes won't stop when it is turned off. Does anyone here know how to diagnose this problem or know where I can download proper diagnostic manuals for this model? I have the Haynes manual, but it is useless for diagnosing errors. It would even help if you know the name of the manual for the 1998-1999 Corolla.

[oldcodger]

Agreed the Haynes manual does not really show how the relay and wiper motor work, its just a grey block on my 2006 diagram.

Refering to mine, ( would assume very similar to yours), the thing to note is that the main wiper switch does not switch Positive, it switches Earth to both the washer motor and rear wiper.

Would suggest the most likey areas of failure are -

Within the switch itself or the wires around the steering column.

Also where the cable loom goes up into the rear hatch, again the wires are subject to movement and therefor breakage or shorts.

Its the latter thats more likely to give you problems, if the insulation is worn off the cable and it touches the earthed metalwork then it will turn the motor on.

Last and I would think most likely, is a fault in the wiper motor or relay ( wherever that relay is ?)

Again any frayed wire could short out or water getting onto the connections around the motor would short things out.

Not sure how the relay is used, but generally wiper motors have an inbuilt contact that keeps the motor running to allow it to complete a cycle, even if you switch off early; so that part could also be failing ( non repairable I think )

Static tests with a multimeter might prove fruitless , I would first start by inspecting around the wiper motor.

Depending on how much, getting a scrappers s/h motor / relay might be an easier way to prove the point if you cannot find a visible fault like a frayed wire.