Modern Vespa

I need help I have a px150 2015 I got fed up with the kph speedo so I thought it would be a good idea to fit a sip speedo how wrong could I have been
I was told it would be easy to fit the power supply box behind the horn caseing and take the wires from the multi plug so this is how far I have got
Red and white-red on box
Black -black ground
Grey there are a couple but all linked together-brown on box
Multi plug on speedo no1-to grey speedo
When you turn the key on it self tests then settled down when you push the starter all the lights on the speedo come on indicator high beam etc also reading half a tank when the original reads full I don't want to start it and do harm
Have I got the wire right can you put the power supply behind the horn case as I can't get it to fit back
If anyone has any photos or has done this please share
Thanks

Aloha. You might want to post this on the not so modern section on here. People will get you your answer much quicker. Good luck

We often have this speedo problem in the US, of course. The commonest solution is to apply vinyl marks and vinyl letters to the face of the original speedo. Websites such as eBay often have precut templates for sale.

Hi after spending £150 on and half a day pulling wire through I hope I can get it sorted