MetaChat - Car people:

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14 December 2006

Car people: How do windshield wiper motors work?→[More:]

I'm under the impression that the typical windshield wiper motor (or, specifically, my parents' 2000 Camry) has two speeds -- low and high. I'm also assuming that intermittent is controlled by the switch on the stalk, telling the motor to go into low speed and turning it right back off. In other words, the intermittent capability is not a function of the motor itself.

The reason I ask is their car, when put on intermittent, turns the wipers on the normal low (constantly wiping) speed, no matter what delay is used on the stalk. No intermittent capability. So my first inclination is to blame the stalk/switch. The guys at the dealer supposedly tested at it and they're blaming the motor. Does this make any sense?

I'm hoping to prevent my dad from spending $100+ on a new motor, if it's just the switch that's bad.

post by: knave at: 20:38 | 4 comments

In most cars, there is a controller circuit board that is often part of the motor, which uses a silicon chip to make a variable time delay pulse circuit. The control stalk has a potentiometer element, whose resistance is varied by some amount as the "interval" setting is changed in the variable range. This change in resistance controls the discharge rate of a capacitor in the control circuit module, thus setting the time interval for the intermittent wipers. If the potentiometer is good (can be tested with a common Digital Volt Meter), the only real fix is to change the controller circuit, which may physically be part of the motor assembly.

posted by paulsc 14 December | 20:47

Ah, that makes sense. So it's possible they're right. Thanks paul!

posted by knave 14 December | 20:48

What paulsc said makes sense. While the whatsit that actually makes the wipers intermittent is not technically part of the motor, it is probably in the same case and impossible to buy the controller separately from the motor.

Mind you, don't take this by any means as a blanket statement that "the guys at the dealer" have any idea of what they are talking about, in this or any other instance. I recently had one of our cars at the dealer to fix a power window, which they had tested and identified as a fault in the regulator, only to tell me after I took the car back to be fixed because parts had to be ordered from Japan that it wasn't the regulator after all and can we have another $600 please, because we didn't really test the regulator, we just guessed (a $175 guess, at that). I told them where they could shove their $600 and to put the car back together how it was. The window still doesn't work ...

posted by dg 14 December | 21:03

Hooray for Robert Kearns who gave us this great invention.

posted by caddis 14 December | 22:00

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