A blown fuse. Or a connection problem within the instrument cluster
If the instrument gauge fuse blows on your 1997 Suburban, you might have an issue with the wiring. An exposed or grounded wire can cause the fuse to blow each time the panel is engaged.
On a 1997 Ford Aerostar : The fuse box is under the instrument panel , on the drivers side
A failed instrument cluster.
A bad ground wire will cause your instrument panel gauges to bounce up and down. The ground wire can be loose or it can be corroded.
Fuse 17 (30A) under the instrument panel.
behind center of instrument panel
http://www.bba-reman.com/content.aspx?content=Jeep_Cherokee_1999_Dash
Used for Interior Lights and Instrument Panel Lights.
Below left hand side of the instrument panel.
try looking on the left hand of the steering column clipped to the instrument panel below the fuse panel.
I was looking at the drawings of the instrument panel ( gauge cluster ) in the 1997 Ford Crown Victoria Owner Guide and it doesn't have a factory tachometer