Can a dimmer switch be bad, but still work?

[custom10nut]

Can a dimmer switch still change the low beam to high beam, but be bad as far as electrical continuity goes?
My dash lights went crazy again, with the high beam indicator, and both the directional indicators stay on. Also, the only light in the dash that works is the one on the far right.
All the exterior lights work fine.
I have one of the screws on the dash housing grounded now, so I am now going to ground the other, just to make sure.