Bosch Purion Speedometer Defect?

[Kurier26]

Hi. Riding a Cannondale Habit Neo 4 with Bosch Performance Line CX 250W.

I've just serviced the pivot hardware. It's been out of action for a couple of months until the parts were acquired, It's unlikely the issue was present before.

After servicing, on first ride, the motor would kick in, but the speedometer would not register the speed and then "Error" would display on the Purion computer display and the motor then switches off. There is no error code given (ie.503), just the word "Error"

I've checked the sensor on the rear wheel is correctly fit and positioned as close to the magnet (cleaned) on the disc as it can be.

I've heard trying to swap the 2 watch batteries in the computer may help, but this tends to be associated with speed discrepancy rather than this issue,and there's no indication the batteries are running low (bright screen and functioning when selecting modes)

The cable connecting the sensor to the computer looks in good nick, but I can't be sure of not kakhandedly damaging the interior when fitting the pivot back together.

Also I'm part way through a gear shifter swap (the error was present before removing this) and there's no chain/gear cable attached to the rear derailleur: I hope I'm right this won't affect troubleshooting the issue?

Any ideas on other potential fixes, or any hints towards a diagnosis from this haphazard info?

I'm trying to prep for potential snow/ice my singlespeed can't handle on my commute to work and don't want to fork out for ice tyres I'll barely use. I' rather avoid the dealer, they're diabolical: I have to check the torques whenever they do anything, I got quoted €250 euros for break pad change (have the replacement set) new chain new cassette and 4 week wait


Any insight or ideas much appreciated

 

[Mikerb]

1. Speed sensor cable damage? Especially where it enters and exits the chainstay. ( less likely given there are specific error codes if the speed sensor is not detected on start up...but worth inspection)
2. Change the Purion batteries..............cr2016 2 off. ( again the Purion has a low battery warning so less likely)
3. operate each Purion button several times with the bike battery out of the bike......just to ensure each button is not sticking.( seems likely especially if for example the on/off button is sticking..........it just says error suggesting whatever is not right is not a recognised error with a code)
4. Start the bike using the bike battery and see how the purion reacts.( avoids using the purion on/off button.....if everything then works it suggests 3) above is in fact the problem.
5. Check the connection on the Purion


How was the bike stored all the time it was unused??

 

[Kurier26]

Thanks for the time taken for a detailed response Mikerb!

1. cable looks fine from the outside but was strained a little during the pivot service so don't know how delicate it is on the inside/could be the problem but as you say, no specific error code.

2. Batteries could be the issue, will purchase replacements/swap, just to rule out.

3. Without the battery attached to the bike, the Purion does not power on, the buttons seem fine. Is not powering on like this normal? Is there a circuit breaker when the battery is out?

Or should it operate without the bike battery installed? If so, then perhaps it is in fact the computer batteries. This bike is a year old & done 5k km, so I'm not sure how long I should expect them to last.

4. When I replaced the battery after step 3, the computer remained off until I hit the power button. I can toggle through with the buttons fine but speed is still not detected.

5. Connection to the Purion seems fine. In the first 30 seconds of riding I can tell it's communicating with the motor because can feel the difference between the mode it is in. It is only after those 30 seconds the system recognises and displays "error" and disengages the motor, I'm assuming because it cannot detect the speed.

I wish Bosch would grant access to their diagnostic software!

The Bike was stored in my basement with the battery removed for a couple of months.


Any further insight greatly valued, but seemingly it'll be going into the dealer! Thanks again

 

[Mikerb]

OK.....with regard to battery ( main battery) removal it was to enable operation of the Purion with no power just to "exercise" the buttons. When replacing the battery I was suggesting switching the bike on using the battery button rather than the Purion. If the fault lies with the Purion on/off button, that procedure would eliminate it.
All the various emtbs operate in a similar way. Pressing the on/off button on the Purion closes a switch which enables a 12v circuit to power up the Purion and begin a start up procedure that consists of sending "hello" data and and getting suitable responses via that 12 volt circuit from all the devices required for start up.............speed sensor, torque sensor, battery. If it recieves confirmation it enables the high voltage circuit from the battery to the motor ( 36v? on a Bosch). The fact your system seems to initiate OK but then fail suggest to me that either the Purion on/off switch is not remaining closed........possibly due to corrosion, which would mean a new Purion is required; or one of the other necessary components has a poor connection or faulty cable.........and that is most likely to be the speed sensor cable.

I had assumed the speed sensor cable may have been left supporting the weight of the rear triangle when you replaced the bearings so some damage may have occured, and yes it could be the actual conductor so not visible.

The other possibility is that tension on that cable dislodged the sensor cable connection at the motor end. So that would be worth checking. If you gain access to that you could also do a continuity and resistance test on the cable with a multimeter.

If you take it to a shop you could save them time by suggesting they first change the sensor cable and Purion.

 

[Mikerb]

To answer your point no 3
All power comes from the main battery. Both the 12v and the 36v circuits. The purion batteries merely power on the Purion backlight I believe.
Keep in mind the Purion contains a processor...so it is a mini computer not just a switch. If you basement is unheated and potentially damp it is possible the Purion was damaged internally. It really needed to be kept in normal household type temperatures and humidity when not being used for so long.

 

[Kurier26]

Ok, thanks for the storage advice.

Checked the cable guides inside the tube and there's a free floating electrical wire

Likely to be the source of the problem as you suspected.

A bit tight and fidly in there and can't see what it connects to, so to an expert it is.

Thanks for your time and have a great "22