HELP NEEDED WITH REV COUNTER/DASH

hi
when i turn my lights on the rev counter drops to zero and the mfa goes mad flashing and fuzzy display. none of the dash lights work. the petrol guage works. also my temp guage is off the scale when cold or hot with the red light flashing for then goes off and then comes on again after 5 secs.

any help much appricated.

thanks

just had the same problem
 2 days ago turned my lights on and every thing hapened same as yours i was gutted i had just changed all the senders on the engine like oil temp oil presser water temp got all my vdos working and changed dash lights to blue so didnt know were to start when everthing went wrong
after changing everthing back when puting oil presser switch back on i saw a lose wire that had snap't of the side of the head got it  back on and everthing was fine i must have snap't it my self gutted had to put all new stuff back on
all fine now but just found out if i push cig lighter in the oil bar vdo go's to max ?  :dontknow:

so the wire is on the right hand side of the head and bolts on to the water hose very small and britlle maybe brown hope it ok mate

earth strap that sound like on top of head to body