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They were getting slower over time until the low power setting stopped working because they would just stop in the middle of the windshield. If I use high they work but are slow. I took the shielding off to get to the wiper transmission and sprayed lithium grease all over the joints. That seemed to work enough to get the low, med and high settings working but they're all about the same speed which is slow. I tried prying the arm off to get a look inside the arm where the joints are to see if the grease has dried up but I couldn't pry it easily and I didn't want something to break.

I'm wondering if this is a mechanical or electrical issue or both. I heard that if the arms are moving then the motor is fine, is this true, or do motors get weak?

 
Rep Power: 228

Youd have to test the motor cicute for voltage and current capacity.

There could also be an issue with the motor control system, the system which let's you select the speed and timing for the blades.

I'm not sure how you would test just the motor, accurately, without load. Perhaps you can test current draw and resistance, while the motor is installed.

 
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Apologies for the very late reply. After spraying lithium grease on the joints the wipers worked a lot better enough to last me in the meantime.

Intermediate doesn't work properly, the wiper blade will stop randomly in a location and never move again. Low works and High works, although I think it's not as fast as it used to be, but fast enough to do the job.

Unfortunately I am electronically uneducated, I have multi-meter but I don't know how to use it lol. You'd have to tell me what lead to put where and how to do it exactly.

If I am able to open and get inside the knuckles of the wiper transmission and properly lubricate it, the wiper should be as fast as before, but the intermediate will still not be working. I feel like this is the motor control system you mentioned, and I'm not sure where that is located on the transmission.

I will add a small detail. When I go from OFF to High the wiper moves VERY fast (probably as fast as it's supposed to be) for one full rotation back and forth, then slows a bit. It's still moving quite fast, but I feel like it used to be much faster.