turning on lights kills my dash!

hi all have prob wit my cab its a 1800 8v when i switch on my head lights my dash lights go out & rev counter stops working, have checked fuses and all ok also when i switch on lights the full beam light shows on dash when i turn full beam on the light to say its on goes out! can anyone help as i have not much hair as it is and am pulling it out!!!!  
thanks

take your clocks out and there is a plug for the clocks, on that plug there is a brown earth wire, it is the second wire, make an earth from somwhere and conect it to this wire, this should solve your problem

thanks will try that

hey! i had this prob, i was scrathcing my head for ages!! found out i left a earth wire of under the engine bay when i swoped the engine over, its only a small earth wire bit like a temp sensotr wire, i earthed it back out again and BO YA dash is perfect.

simon