My fix for the Infamous parking brake failure!

[lugnut1009]

I recently had to do a lot of work on my wife's F3 and wanted to share my findings since I wasn't able to find much when I was searching myself. I understand a lot of people take their bikes to the dealer when it gets past minor repairs or maintenance, but that's about all I found was "took it to dealer and they replaced the parking brake motor". I dove into this myself, and while I didn't take any pictures, I wanted to share my experience anyway in case it could help someone else in the future.

Back story if interested, if not skip to next paragraph:
This all started with a simple brake fluid change out and pad replacement. First problem I encountered was a failed rear caliper (seems snap ring popped out of the threaded portion internal to the caliper while attempting to press and thread the piston back into the caliper) which cost me over $500 and a couple weeks of down time. After that fiasco, put the new caliper on and the master cylinder goes to leaking! :gaah: I think the vacuum brake bleeder I was using took out an already worn seal in the master cylinder. So another $320+ for that and another 2 weeks down. This time I bled the brakes the old manual way with my wife as the pedal pusher. Finally success!! Or so we thought. So now the electric parking brake won't move or even make any attempt to move at all.

Parking brake failure:
Ok so I removed the side panel and disconnected the bullet connectors going to the parking brake motor. I measured voltage with the motor disconnected and the bike is sending 12v to the motor in both directions which obviously tells me it's the motor. I removed the motor, just three screws that are horrible to get to, and removed from the bike. By this point you will realize this motor is very similar to an '80's automobile electric window motor. I took it apart and couldn't really find anything wrong. The only thing I noticed was the brushes were worn funny, and there is absolutely no lubrication in there. So I applied just a little grease, reassembled, and tested with an old battery I happen to keep in my shop on tender. Worked great! So I reinstalled and the brake works as it should. But due to the motor brushes being worn I'm going to order a new one.

Long story short, if you have 60k miles on your bike, it sits up for a month and the parking brake motor doesn't want to work for the first time ever, just buy a new one... They aren't hard to replace just expensive ($210+), like everything else on this bike.

 

[Haze]

Very nice write up. Hope all goes well with the new motor once received.

 

[Peteoz]

Thanks lugnut…….very informative:thumbup:

Pete

 

[BertRemington]

lugnut -- great description. I'm trying to understand the failure mechanism. In most cases it appears to be the parking brake motor, not the WPM nor the pulley switch nor the console switch.

The motor is a DC permanent magnet coaxial drive into an enclosed apparently high-ratio worm gear pair (which provides the engaged/disengaged locking mechanism) and then into a steel/nylon spur gear pair, the nylon portion operating the brake cable. There is a fixed position switch for the pulley which connects to both the WPM and the console. The nylon gear has two "pulley stoppers" 180 degrees apart which operate the switch. Alignment of the nylon gear to the switch and the cable is critical (as is cable adjustment).

Here's where it gets weird. There are two stoppers and one switch. Nothing surprising except the 180 degree nylon gear rotation seems much longer than cable travel or pad tensioner travel would allow. After studying the service manual I believe the low stopper is for 1330cc models and the upper stopper is for 990cc models.

Therefore when the stopper contacts the switch, the switch closes signaling the WPM and console the parking brake is engaged signalling the WPM to stop motor power (although current draw might also be a factor).

For disengaging the brake how does the WPM determine when to stop motor power? The stopper ramp is too short so it's either current draw or time.

Members reporting this failure say the motor isn't operating. This can occur for two reasons: (1) the motor drive is jammed; and (2) the motor isn't drawing current. In the first instance, I would think there would be some noise as the motor tries to operate albeit for a short time. In the second instance, the WPM thinks the motor has disengaged even though the switch says otherwise or the WPM is trying to operate the motor but the brushes aren't supporting the requisite current flow (which based on #18 wire is probably 3-5 amps).

Why isn't this failure occurring more often? The two most likely reasons are: (1) loss of production quality for certain model years; or (2) pressing heavily on the brake pedal during parking brake motor operation. The first instance seems more likely but as I can feel motion in my brake pedal during motor operation I've made it a point to rest my foot lightly on the brake pedal.

 

[lugnut1009]

lugnut -- great description. I'm trying to understand the failure mechanism. In most cases it appears to be the parking brake motor, not the WPM nor the pulley switch nor the console switch.

The motor is a DC permanent magnet coaxial drive into an enclosed apparently high-ratio worm gear pair (which provides the engaged/disengaged locking mechanism) and then into a steel/nylon spur gear pair, the nylon portion operating the brake cable. There is a fixed position switch for the pulley which connects to both the WPM and the console. The nylon gear has two "pulley stoppers" 180 degrees apart which operate the switch. Alignment of the nylon gear to the switch and the cable is critical (as is cable adjustment).

Here's where it gets weird. There are two stoppers and one switch. Nothing surprising except the 180 degree nylon gear rotation seems much longer than cable travel or pad tensioner travel would allow. After studying the service manual I believe the low stopper is for 1330cc models and the upper stopper is for 990cc models.

Therefore when the stopper contacts the switch, the switch closes signaling the WPM and console the parking brake is engaged signalling the WPM to stop motor power (although current draw might also be a factor).

For disengaging the brake how does the WPM determine when to stop motor power? The stopper ramp is too short so it's either current draw or time.

Members reporting this failure say the motor isn't operating. This can occur for two reasons: (1) the motor drive is jammed; and (2) the motor isn't drawing current. In the first instance, I would think there would be some noise as the motor tries to operate albeit for a short time. In the second instance, the WPM thinks the motor has disengaged even though the switch says otherwise or the WPM is trying to operate the motor but the brushes aren't supporting the requisite current flow (which based on #18 wire is probably 3-5 amps).

Why isn't this failure occurring more often? The two most likely reasons are: (1) loss of production quality for certain model years; or (2) pressing heavily on the brake pedal during parking brake motor operation. The first instance seems more likely but as I can feel motion in my brake pedal during motor operation I've made it a point to rest my foot lightly on the brake pedal.

I think it’s monitoring motor amperage and utilizing the physical switch for the brake disengaged safety confirmation. I also attribute this failure to low quality manufacturing, but I can’t say it’s terrible because it has lasted nearly 60k miles and this is the first hiccup we’ve experienced with it.

 

[Tucker01]

Hello Lugnut . I am having issues with my parking brake motor 2018 f3 limited . If I disconnect the cable at the rear and push the switch the park brake motor will work . When I reconnect the cable and activate the park brake motor, it will engage the park brake , but usually only once or twice , then I have to disconnect again and leave it disconnected. Do you think it’s the motor ? I’ve ordered a new one .

 

[lugnut1009]

Hello Lugnut . I am having issues with my parking brake motor 2018 f3 limited . If I disconnect the cable at the rear and push the switch the park brake motor will work . When I reconnect the cable and activate the park brake motor, it will engage the park brake , but usually only once or twice , then I have to disconnect again and leave it disconnected. Do you think it’s the motor ? I’ve ordered a new one .

Sounds like a weak motor, but you may be able to adjust the parking brake tension too so it’s not pulling so hard. The parking brake really just needs to keep it from rolling, doesn’t have to be so tight.

 

[Tucker01]

Got it Thank you . I have a new motor on order . Ride safe ��