I have intermittant problems with my tach, gas guage,dash lights, and brake lights. they either go off and on randomly, or read wrong (gas guage) Could this be a grounding problem. Where do I start to try to find the problem?

Sounds more like alternator intermittent failure to me - I just went through this with my 90 Legacy last year.

 

Had an aftermarket alt installed in the car (the one with the "lifetime" warranty*) for about a year - dash lights started flashing on/off randomly after the car had been run for about 20 minutes.

Went back to the parts store to get it tested, it would test just fine every single time - yet I was still having problems - I went through every single ground on that car! and still had problems...and of course the parts store wont warranty it unless it tests bad.

 

I finally took an old stock unit I had to a local rebuilder, and had it rebuilt. Put that in the car, and have not had a problem one since then. It cost me a bit more, but has been worth it.

 

And I DID get my parts store alt replaced finally - it now sits on a shelf in it's box as a backup.   

 

* that was actually like the 3rd "lifetime warranty" alternator I had had in this car - they would only last about a year before failing...

There are a bunch of badd alts out there right now.

 

Problem is with the "sense" circuit in the alt which is the Yellow wire.  That wire is tied directly into the ECU power supply.

 

Try disconnecting the plug that goes to the alt, and see if the issue stops.

 

If that isn't it....the dash grounds through a big fat Black/yellow wire that bolts to the chassis on the passenger side of the tunnel, under the far forward corner of the center console.  That wire has a big spade connector about 12-18" up the wire from where it bolts in.  This connector can get hot, melted, corroded by spilled soda etc.......check it.

I agree with Gloyale. I think you will find out the alternator is causing the trouble.