Here's why it's more likely to be the motor or module:
* Intermittent wipers use a timed circuit: This circuit is integral to the motor or control module. A faulty component in this circuit causes inconsistent wiping speeds and the jerky movement you're experiencing.
* Switch failure is usually more binary: A bad switch would likely result in wipers not working at all, intermittent mode not engaging, or constant speed only.
Troubleshooting Steps:
1. Check the fuses: A blown fuse related to the wipers would prevent them from functioning entirely.
2. Inspect the wiper linkage: Ensure there's no binding or damage in the linkage that connects the motor to the wiper arms. Stiffness or obstructions can cause jerky movement.
3. Try different intermittent settings: If the jerkiness is only present on certain intermittent speeds, it further points towards a problem within the motor's speed control circuitry or the module.
4. Test the motor (if accessible): If you're comfortable working with car electronics, you might be able to access the motor and test its operation directly (but this is difficult and potentially dangerous). You might hear irregular clicking or grinding sounds that further confirm motor issues.
Which to replace first?
It's more cost-effective to attempt repairing or replacing the wiper motor first. The control module is more expensive and complex to replace. If replacing the motor doesn't solve the problem, the control module is likely the culprit.
In short: While the switch isn't entirely ruled out, the symptoms strongly suggest a problem with the motor or its control module. Start with a thorough visual inspection and fuse check, then consider the motor as the most probable cause.
