Trail tech vapour Tach hookup

[06EC300]

I am trying to hook up the tach wire on my vapor gauge....I attached the yellow wire under my seat to the red wire to the gauge and then grounded the black wire to the chassis.

When i fire the bike up the gauge seems to work fine at idle but when I rev the bike the gauge goes backwards.



I also tried the yellow wire that runs up to where the headlight is same thing happens



Any ideas on how to fix that?

bike is 06 EC300