Dash light failure and idle RPMs for 1996 Saab 900S

My '96 Saab 900s dash light failed when turning my lights on. Sometimes when I push on the dimmer knob the dash light will come on, and then go off real quickly.
How can I fix this as a nuisance driving at night and not being able to see my speed?
Additional question:
What is a normal idle RPM for '96 saab 900s? I thought I heard 800RPMs. My car idles at 11-1200RPMs. If this is high, I’m probably wasting fuel. What would be some ways to correct this?

You probably have to replace that dimmer. You could try some radio shack contact cleaner and spray it in but more often than not it will need replacing.

My 900 turbo was idling around 800.My 900S was a little higher, I seem to remember.
If that speed is consistently higher, it could just be a simple adjustment on the throttle body.
It if bounces around and/or it is sometimes higher/sometimes lower, it would likely be due to a vacuum leak somewhere or the IAC (Idle Air Control) valve.