2007 WRX, Wipers have a mind of their own!

Dec 5, 2022
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The wipers on my 2007 WRX will go on without the wiper selector being in the on position. They may stay on for a long time or they turn off. Totally random. I have replaced the wiper motor. I have replaced the wiper selector. They still are possessed. One strange thing. When the car is off but the accessories are one, the wipers respond correctly to the wiper selector position.

Have you added any accessories or components that do not belong to the vehicle?
Are the replacement parts a direct fit and matching part number?
No accessories have been added, but this car was heavily modded and then returned (to mostly) stock before we purchased it. It only happens in the wetter months of the year. During the summer all is fine. If water was getting into the wiring harness that connects the washer pump would that create a short issue?
Glad you pointed that out about modifications. One test is with an Ohm meter, check to see if the fluid in the tank has continuity. As for the harness, if for some reason the harness "wicked fluid" to the controls at the steering wheel, then you have a good argument. I am suspecting something else when mentioning "wetter months" and now you need to pay attention to any interior water leaks onto any controller. One test is with all doors closed, a few lights and have a partner water the exterior (front or rear end) to look for water leaks. I have seen a few with leakage at the sunroof drains into the interior (behind panels / onto control units etc.)
If the battery and or electrical system has no parasitic draw, look at the "removed" modifications and how the vehicle was returned to the stock version.
Sometimes, not all the time, lighting modifications can also cause unwanted / uncontrolled component wake up or inactivity.
Another hint is with the mention "Assy ON" and the wipers operate normally. Check / test for AC ripple and or leaking diodes at the alternator. The same test can be performed and at the fused connections.
You will need an oscilloscope to measure AC ripple.
Been down that road before.
Use key words - Automotive AC ripple test

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