Defective motor temperature sensor

[KaFr]

If the temperature sensor inside the motor fails, it is almost impossible to replace it with a new one.
This sensor is encapsulated in the insulation of the stator winding, as can be seen from the photo.

[HadesOmega]

Wow I am surprised some of the engineering of this bike they made it too complicated to work on =/

My plan was to buy a new thermistor and plug it in to the harness and stuff it into the wiring cavity.

[Leander]

It's a parker motor (GVM 142 custom winding), not designer by Brammo them self.
Sensor does not need to be inside the winding putty but it will make the vallues closer.
I run my replacement sensor just snugged up to the windings. It works but with a 10deg lower temp.

[HadesOmega]

I think it's just better to disconnect it.  I don't see any problems that would arise from the waterpump being on all the time.

[EV promise]

Hi, regarding the motor temperature and the water pump, any ideas for the critical temps, it's a variable speed pump?  No mention in the log files, doesn't show on the software screens. Pump is quiet when I first turn the bike on but humming away  when the motor warms up and I stop or park up. Thanks

[HadesOmega]

Not sure, I think it is just on and off.  I forget what temp it kicks on.  If you could plug in a potentiometer to adjust the resistance you might be able to adjust the motor temp reading and find out when it kicks on.

[new-brammo-guy]

I'm debugging the identical motor temp issue HadesOmega's had and described in the thread above and this previous one: https://brammoforum.com/index.php?topic=3963.msg27567#msg27567

[1] The normal / stock motor thermistor should read about 575 Ohms at 15-20 degrees C, though mine reads 471 Ohms, which is why my temps are -20 C (as described by HadesOmega). I also have the corrosion issues on the motor lugs.

[2] The coolant pump turns on at 36 degrees C, which is when the thermistor resistance should be ~645 Ohms.

[3] I've attached the thermistor specs from the Victory Empulse manual. The same thermistor part number is available online (e.g. Amazon, etc.).

[4] I've attached a plot of Temp v. Resistance based on the data I collected using a potentiometer and pasted below. Also included the plot from this datasheet of the thermistor:
https://hdd.se/wp-content/uploads/sites/6/2021/08/resistance_kty84_130.pdf

Temp On Dash (C)   Resistance in (Ohms)
7   518
12   544
24   588
27   601
31   617
32   622
32   623
33   628
34   630
35   638
36   645
36   640
49   700
101   1000

[new-brammo-guy]

Has anyone figured how why the motor thermistor fails? I added a potentiometer in series to see if I could solve it by bringing the resistance up by ~100 Ohms or so into the normal range. But the resistance of the thermistor still fluctuated quite a bit (i.e. doesn't work).

I'm thinking that the only fix would be a replacement thermistor (KTY 84-130, PTC, https://hdd.se/wp-content/uploads/sites/6/2021/08/resistance_kty84_130.pdf)

Leander mentioned he replaced his thermistor and put it "snugged up to the windings" though I don't know exactly how he did this.

Any thoughts?

Thanks a lot.

[Leander]

essentialie I put the thermister into the sleeve of the old thermister cable as far as it will go.

temp does read a steady 10C lower this way but I believe this is good enough.

[new-brammo-guy]

Thanks a lot for the info Leander.

Leander, a few more questions:
[1] Did you repurpose the Air Temp thermistor? If so, do you have a picture of where it was located? I don't see anything in the manual about the Air Temp specs + location.
[2] Or did you buy a replacement thermistor (attached datasheet): https://www.digikey.com/en/products/detail/nxp-usa-inc/KTY84-130-113/1068979?s=N4IgTCBcDaIAQGkAqBNOAOALAWgIwGYAGEAXQF8g
[3] Have you tried to add a small resistor in series with the thermistor to increase the temperature by 10 degrees C?
[4] Did you also have corrosion on your three motor bolts (see attached pic from HadesOmega's - mine looks similar though not quite as bad)?

Thanks again