I've had great help here on the forums before so let's see if anyone's had this issue before.
Ok I start car, all gauges work good. Switch on thE headlights and all the gauges go to the top/max , speedo and tach quit , dash lights don't come on.
Switch lights off ...all gauges work good again.
Repeat til it gets boring.
Any suggestions ? , I've never been into the dash of this car before .

 

Almost certainly a poor ground/earth at the instrument cluster.

Poor/corroded connections at the back of the instrument cluster are common. Remove cluster (fairly easy task) and carefully clean all contact points and connectors...AND add a redundant ground wire


Cheers
DD

 

I agree with Doug. Probably a bad ground or connection on dash

 

Only a few screws to take off and some connections in the back of the instrument cluster. Pull the steering wheel off... You will need a 13/15" socket... just put the wheel in the center position. When you take the cluster off, there will be a metal piece on the back of the panel. Clean it off, rough it up a little and reinstall.
ken in wv