I'm wireing my boost gauge in at the moment.
The gauge has got the following wires

+12v battery
+12v battery switch
Ground
I've wired it in to fog light switch. I was told it would be ok to connect both 12 v supply and 12v switch together so I wired both of them to the switch wire on fog light switch.
Now when I put ignition on my headlight are on. Even though the headlight switch is in off position, then if I put headlight in on position the boost gauge goes off and headlights stay on
Can anyone please help

 

Sounds like you've gone to the wrong side of the switch. Either try the other side or simply run a +pos from the center console ie head unit/cig lighter. Hth

Also where have you earthed it to?

 

have you accidentally knocked the switch on the top of the steeing column which brings the parking lights on?

 

No not knocked switch. I've earthed it to the fog light switch

 

Ok, wired it at the back of the head unit and all is well, thanks.
It's a digital boost gauge that reads in psi. When the cars ticking over it reads -10. Is this correct and what should it go to when I give it the beans. Cheers

 

Nice one Yeah it will read negitive/vacume on tick over, not sure what the boost is on your MY but would think 12 to 15 psi ish

 

Yes i gather that your off boost until you start getting +numbers, im sure i had it up to about 20 so think its working ok.
Thanks for yoour help, much appreciated

 

Yeah thats correct, will also go -neg on over-run too. As i said dont know the specs for your MY but 20psi sounds alot Your welcome any time, glad your sorted