possible computer multiplex issue
 

Does a 91 civic have a computer multiplex? If so could it cause the gauge illumination to work intermittently then burn out the gauge backlight bulbs? Also I replaced the dimmer switch already and the lights were intermittent now have been out for a while. Thanks for any help or info.

I seriously doubt that the ECU has anything to do with the cluster light circuit (switching the main light switch to "marker" lights turns the cluster lights _on_; I think, the ECU only reads the speed sensor in the cluster.).
More than likely the cluster light sockets are: (a)dirty, (b)not connecting securely with bulbs, or the power and/or ground to that light circuit is intermittent.