eBrake failure

[flybobbie]

Well last set of traffic lights coming home, pulled switch, no park brake and amber warning.
So read the codes.
Interesting the car has been suffering from unstable cold starts for some months, idle fluctuating for 5-6 seconds then settles. Bit random.
I am beginning to think that ambient temp. sensor is throwing a wobbly.
It was reading 16 degrees, which agrees with the temp. outside. But could be intermittent.
I'm wondering if the knock on effect is the eBrake system is not sure what the ambient temp. is so refusing to operate the brake.
The emergency function works ok, so the switch works.
One ebrake motor on the left did work for a moment, can be seen 20knf.

pbf.jpg (92.84 KiB) Viewed 618 times

So that's my bank holiday sorted.
Think i will just go to the dealer Tuesday and buy another sensor.
Also cost out motor replacement part.
Actuator counter is also different left and right ("left" on bottom line i think is a Foxwell naming error).
I wonder if the right has been failing to lock.
Temp. sensor and ebrake problem might just be coincidence.

[Ole gits rule]

The brake failure is normally due to poor battery and needs a software update to correct it, normally throws a wheel speed sensor error

[flybobbie]

Just ordered some motors and sensor online cheap enough.

[flybobbie]

The brake failure is normally due to poor battery and needs a software update to correct it, normally throws a wheel speed sensor error

Well will see next week when the parts arrive, i'm not suspecting battery.

[Chippie]

The brake failure is normally due to poor battery and needs a software update to correct it, normally throws a wheel speed sensor error

Well will see next week when the parts arrive, i'm not suspecting battery.

What makes you think it’s not the battery? And how old is it?

[flybobbie]

Battery about 3 years old.
Have a volt meter fitted always well over 12 volts.

[Ole gits rule]

The brake failure is normally due to poor battery and needs a software update to correct it, normally throws a wheel speed sensor error

Well will see next week when the parts arrive, i'm not suspecting battery.

My car had the brake failure before when I went to pick it up, the garage spent a week trying to fix the issue despite me telling them it needed a new battery and software update.

They finally gave up and sent it to BMW and it was sorted with the update and a new battery - your could be very different so you have to try what you feel is going to cure the issue.

[flybobbie]

l tried this morning. Left came on briefly, right never tried.
So the right one has failed.
It can be seen by the actuator count discrepancy on the obd readout that the right has not kept up with the left actuator.

Difference is 92, so for me that is about 10 days driving.

Car has done 95k miles, mainly commuter 15 miles per day.
So averages out ebrake applied every 3 miles.

Can't complain, i have not had to crawl under the car just before MOT to adjust the parking brakes like every other car i have owned..
Don't even mention the stupid design of park brake on Mazda RX-7's, always leaking brake fluid.

[flybobbie]

Well all sotrted.
Replaced temp. sensor. Cleared the codes.
Might have made some difference.
First time for a while i have seen 32mpg on spirited drive home.

Next replaced both ebrake motors.
Had to operate the ebrake switch several times in order to allow the code reader to erase errors, although they went away on car no problem.
So reader was only needed to clear the historic error.
Took some multimeter reading on the motor gearbox contacts, someone without code reader might find useful.

BRAKE.jpg (79.19 KiB) Viewed 488 times

Can see the faulty motor showing 4.8 k ohm across outside contacts.

When i have more time i will cut the faulty one open, see what's inside.

[Chippie]

It’s good to see you got it sorted and thanks for posting results

[flybobbie]

I did measure the temperature sensor, it was 4k ohm at 20 degrees.
The old one seemed fine, but the new one allowed me to cancel it's faults, so something was wrong with it.

[flybobbie]

Seems corrosion killed it.

brake1.jpg (87.16 KiB) Viewed 431 times

Only connection to outside world is the clearance around the planetary gear housing.
There is a rubber O ring when fitted to the caliper. Moisture must still get in.
Not sure if some rubber safe grease would do no harm to keep moisture out.

brake2.jpg (76.97 KiB) Viewed 431 times

[B21]

I had one fail..the plastic casing had a micro crack in which allowed water to enter..full of rusty water..

[flybobbie]

Seen it on street electrical equipment. Component gets warm, air inside expands escapes through micro gaps..
As it cools draws in moisture and cycle repeats. Like a thermal pump.
Open up to find condensation inside and rusty electrics.