Hub dynamo & bike computers

[A T McBean]

Hi folks! I have a Giant Lafree twist ebike with a Giant Axact 6 wired computer. This has worked well, HOWEVER I recently changed my front wheel to a Shimano Nexus hub dynamo and now the computer doesn't work (no speedo or odo)
If I put my original wheel on it works fine!
Does anyone have any idea why?
The only thing I can think of is the dynamo producing an electro-magnetic field causing interference
Any suggestions gratefully received!
Thanks!

 

[C R]

Is there a magnet in the original wheel which is missing in the new one? The magnet will usually be attached to a spoke.

 

[si_c]

Is there a magnet in the original wheel which is missing in the new one? The magnet will usually be attached to a spoke.

^^ Very much this.

 

[figbat]

Is there a magnet in the original wheel which is missing in the new one? The magnet will usually be attached to a spoke.

I was going to say the same thing. Or perhaps another similar setup - for example on my old motorbike the speed sensor used the brake disc bolts as the counting medium - people used to replace the bolts with stainless or titanium ones and wonder why the speedo stopped working.

 

[Ajax Bay]

a Giant Axact 6 wired computer

This wire you mention: where are its two termini (on the bike) axactly?