Wiper Motor Mishap: August 7, 2020

For the past 5+ years, my wipers will intermittently malfunction on my 2000 Chevy S-10. When the wiper selector on the multifunction switch is placed on any of the delays, the wiper blades will continue as if the selector was on the "Low" position.

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Diagnosis

Determining whether the problem lies in the Multifunction Switch or the Windshield Wiper Motor Module is not an easy task. The resistors that control the pulse are located in the Multifunction Switch which could bring one to conclude that the problem is in the switch and not the module. Luckily, I have a Mitchell 1 DIY account with my former 1999 Chevy Tahoe listed as a vehicle on there. Being that my S-10 is a 2000 and made by General Motors, there are a lot of similarities between my S-10 and Tahoe with quite a number of components having the same part number. So, I logged onto Mitchell 1 DIY and printed out any relevant information to help in the diagnostic procedure (I added the printout as an attachment to this post below).

Wipers_99Tahoe.pdf

Download PDF • 1.06MB

There are a couple differences in the wire colors which can be compared to the pics posted above that display pages out of my service manual for my 2000 S-10 pickup. Here is a list of the actual pins for the Windshield Wiper Motor Connector on a '00 S-10:

Pin Wire Color Function

A Dark Green Windshield Wiper Switch: On

B Black Ground

C Yellow Fuse Output: Accessory

D Purple Windshield Wiper Motor Feed High Speed

E Gray Windshield Wiper Switch: Low/Pulse

Note: these values can be seen in one of the pics posted above.

From the procedure listed in the Wipers_99Tahoe document, the problem with the faulty wiper blade operation on my 2000 S-10 pickup is due to a malfunction with the Windshield Wiper Motor Module. After disconnecting the connector to the wiper module, wiper switch off, and with the key-on-engine-off, I did not find power at Terminals E or D therefore ruling out any problem with the wiring or Multifunction Switch. The Wiper Motor Module is part of the Windshield Wiper Motor but can be ordered and replaced separately as its own component.

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Left: the assortment of pics from a few different manufacturers show what a Wiper Motor Module looks like for a 2000 Chevrolet S-10 pickup truck.

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Diagnosis (continued)

Due to the above diagnostic procedure from Mitchell 1 seeming a bit sketchy, I wanted to be absolutely certain that the Wiper Motor Module was indeed the culprit. I needed to analyze the circuit schematics and determine if another method existed to distinguish where the problem lies. After further review, I figured that I could backprobe Pin E at the connector to the module and read the amount of voltage present to the module while it is operating in Low and all five of the delay speeds during the time it is NOT malfunctioning. Then, when the wipers do act up, the voltage measurement can be taken and compared to the good known measurements. If the voltage values line up (within reason), then the problem is indeed within the Wiper Motor Module. However, if the voltage of the delay setting is equal to the Low speed value, then the problem is either in the Multifunction Switch or the wiring between the switch and the module.

Upon analyzing the voltage at Pin E, I found that during all five delay settings the voltage fluctuates between zero, when the wipers oscillate, to a value ranging from 2.1-2.3V in which the voltage slowly builds back up to the latter amount. Continuing on, the voltage with the wipers set to Low remained fairly steady around 11.5V. My GM service manual states to disconnect the Multifunction Switch connector during the time it is malfunctioning. This complicates matters because the switch connector is hard to get to and the wiper motor mishap doesn't happen that often and only lasts for a very short amount of time.