Wiper Parking Position Problems
Blue Bowtie
06-12-2007, 12:01 PM
Many GM W-Bodies (and several other series) have a similar mechanism and method for parking the windshield wipers below the hood line at the cowl. Other than minor positioning problems, some have experience their wiper arms parking in other places, typically at the top of swing of the wiper arm arc. If that's been your experience, this may be of interest.
The wiper motor operates in a normal (forward) direction to turn the linkage and raise the wipers, then sweeps them across the windshield, just as we would expect.
When the wipers are turned off, the wiper motor operates in the reverse direction to park the wiper blades. The mechanism uses a cam plate, a spring-loaded friction disc, stop pawl, and a slide switch to sense the end of the park travel and stop the wiper motor. If the pawl does not engage the intended stop tab, the wiper motor will run in reverse until it encounters a restriction, whereupon the cam plate will slide the switch and stop the wiper motor. That is often at the end of travel or sweep of the wiper arms (all the way up).
When the wiper arms are restrained from their normal movement and the motor is turned on, the motor can twist in its mountings from the extra load. This load can force the cam plate to crush/bend the metal stop tab, rendering it useless. This is why it is important to clear the wipers of any snow, ice, or accumulation before operating them. That is usually mentioned in the owner’s manual, but next to civil statutes and ordinances (and speed limit signs), those are probably some of the most unread publications ever printed. After all, everyone knows how to use and care for a vehicle, right?
Regardless of how or why the damage has occurred, the repair does not have to be difficult or expensive in many cases.
Although GM has published several Technical Service Bulletins regarding the problem and the repair, the TSB suggests replacing the mounting plate and stop tab. That may seem unnecessary and excessive, but it’s not necessarily self-serving. There is no way for a technical writer in Flint to know just how mangled the mount and tab might be on every vehicle with this problem. A new mount and tab are known to have the correct angles and dimensions, and have not already been weakened by abuse, thus the indicated replacement to correct the problem.
For those who may not want to replace the hardware, repairing it may be an option. Even if replacement is required, the steps outlined here should be useful as a guide.
Remove the wiper arms. This may involve removing a trim cap and nut and using a puller to remove the arms on some vehicles, or simply engaging a stop lever and removing the complete arm on others. Most times it will require removal of a washer hose as well.
Once the wiper arms are off, the cowl trim must be removed. There are several fasteners holding on the trim, ranging from push-pin rivets to screws. Some models have the cowl trim split into two halves, and only the left side would need to be removed. Many vehicles will require that the cowl seal be removed or at least pulled back slightly to remove the cowl trim.
With the wiper arm(s) and cowl trim piece(s) removed, the wiper motor cover should be visible. There is typically a single clip or push-pin rivet holding the wiper motor cover to the mount. Remove the fastener or clip and lift out the cover.
http://mysite.verizon.net/strey/files/WiperMotorCover.jpg
Beneath the cover is the stop/park cam mechanism. There should be a plastic cover snapped onto the cam which can be removed easily. This reveals the cam, stop pawl, and mechanism clearly.
http://mysite.verizon.net/strey/files/WiperCamCover.jpg
On the left edge of the opening in the mounting plate, a small tab should be extending through the opening. This is the tab which is likely crushed/bent. It should be plainly visible as the twisted, rusted piece:
http://mysite.verizon.net/strey/files/WiperStopTabRevealed.jpg
Turnon ignition power, clear everything from the wiper area, and operate the wipers. Turn off the ignition switch when the wiper cam/mechanism is in a position which affords the best access to the stop tab.
http://mysite.verizon.net/strey/files/WiperStopTabBent.jpg
The tab should be perpendicular (90º) to the surface of the mounting plate. Use whatever tools are suitable to form the tab back to its intended position.
http://mysite.verizon.net/strey/files/WiperStopTabStraight.jpg
Assure that everything is clear (including people parts) of the mechanism. Turn on the ignition and test the wiper operation. When the wipers are switched off, observe the cam and pawl action, making sure they contact the stop tab fully. Adjust as necessary. Before final assembly, you may want to apply some lithium grease to the stop tab and pawl to minimize wear.
http://mysite.verizon.net/strey/files/WiperCamGreased.jpg
Remember to snap on the cam cover and install the motor cover before replacing the cowl trim and wiper arms. If the wiper motor has parked correctly, the wiper arms can be installed in the fully retracted (PARK) position. Test them again to verify proper operation, including the washers. Be prepared to turn off the ignition power to prevent damage, just in case...
The wiper motor operates in a normal (forward) direction to turn the linkage and raise the wipers, then sweeps them across the windshield, just as we would expect.
When the wipers are turned off, the wiper motor operates in the reverse direction to park the wiper blades. The mechanism uses a cam plate, a spring-loaded friction disc, stop pawl, and a slide switch to sense the end of the park travel and stop the wiper motor. If the pawl does not engage the intended stop tab, the wiper motor will run in reverse until it encounters a restriction, whereupon the cam plate will slide the switch and stop the wiper motor. That is often at the end of travel or sweep of the wiper arms (all the way up).
When the wiper arms are restrained from their normal movement and the motor is turned on, the motor can twist in its mountings from the extra load. This load can force the cam plate to crush/bend the metal stop tab, rendering it useless. This is why it is important to clear the wipers of any snow, ice, or accumulation before operating them. That is usually mentioned in the owner’s manual, but next to civil statutes and ordinances (and speed limit signs), those are probably some of the most unread publications ever printed. After all, everyone knows how to use and care for a vehicle, right?
Regardless of how or why the damage has occurred, the repair does not have to be difficult or expensive in many cases.
Although GM has published several Technical Service Bulletins regarding the problem and the repair, the TSB suggests replacing the mounting plate and stop tab. That may seem unnecessary and excessive, but it’s not necessarily self-serving. There is no way for a technical writer in Flint to know just how mangled the mount and tab might be on every vehicle with this problem. A new mount and tab are known to have the correct angles and dimensions, and have not already been weakened by abuse, thus the indicated replacement to correct the problem.
For those who may not want to replace the hardware, repairing it may be an option. Even if replacement is required, the steps outlined here should be useful as a guide.
Remove the wiper arms. This may involve removing a trim cap and nut and using a puller to remove the arms on some vehicles, or simply engaging a stop lever and removing the complete arm on others. Most times it will require removal of a washer hose as well.
Once the wiper arms are off, the cowl trim must be removed. There are several fasteners holding on the trim, ranging from push-pin rivets to screws. Some models have the cowl trim split into two halves, and only the left side would need to be removed. Many vehicles will require that the cowl seal be removed or at least pulled back slightly to remove the cowl trim.
With the wiper arm(s) and cowl trim piece(s) removed, the wiper motor cover should be visible. There is typically a single clip or push-pin rivet holding the wiper motor cover to the mount. Remove the fastener or clip and lift out the cover.
http://mysite.verizon.net/strey/files/WiperMotorCover.jpg
Beneath the cover is the stop/park cam mechanism. There should be a plastic cover snapped onto the cam which can be removed easily. This reveals the cam, stop pawl, and mechanism clearly.
http://mysite.verizon.net/strey/files/WiperCamCover.jpg
On the left edge of the opening in the mounting plate, a small tab should be extending through the opening. This is the tab which is likely crushed/bent. It should be plainly visible as the twisted, rusted piece:
http://mysite.verizon.net/strey/files/WiperStopTabRevealed.jpg
Turnon ignition power, clear everything from the wiper area, and operate the wipers. Turn off the ignition switch when the wiper cam/mechanism is in a position which affords the best access to the stop tab.
http://mysite.verizon.net/strey/files/WiperStopTabBent.jpg
The tab should be perpendicular (90º) to the surface of the mounting plate. Use whatever tools are suitable to form the tab back to its intended position.
http://mysite.verizon.net/strey/files/WiperStopTabStraight.jpg
Assure that everything is clear (including people parts) of the mechanism. Turn on the ignition and test the wiper operation. When the wipers are switched off, observe the cam and pawl action, making sure they contact the stop tab fully. Adjust as necessary. Before final assembly, you may want to apply some lithium grease to the stop tab and pawl to minimize wear.
http://mysite.verizon.net/strey/files/WiperCamGreased.jpg
Remember to snap on the cam cover and install the motor cover before replacing the cowl trim and wiper arms. If the wiper motor has parked correctly, the wiper arms can be installed in the fully retracted (PARK) position. Test them again to verify proper operation, including the washers. Be prepared to turn off the ignition power to prevent damage, just in case...
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