Hi XJ6Fred,

Welcome to the forum.

What exactly do you mean by "dash lights"?

Do you mean what is termed "locate lighting" in the dash as if you turned the headlights on for instance?

Are the gauges still working after you remove the key? Warning lamps still on?

You may have a bad dimmer switch.

The Lighting Logic Unit does send a signal to the dimmer when the fascia Lighting Switch is closed. It may be faulty.

It could be something else like a shorted wire for instance.

It's hard to say precisely w/o doing some electrical tests first.

Do you know how to perform voltage tests with a test light or preferably with a multimeter?

 

On your 91 it is the dimmer switch, remove the bottom of the steering column (two screws) look under and follow the wires from the dimmer switch to it's module, then see if the module has two connectors or one, search ebay for a replacement. If it is good your troubles are over.
Oh, you can remove the module without ripping apart half of your car, just remove that bottom cover, remove the nut from the dimmer switch pull it out then carefully pry the module from the mounting bracket (it is held in place by plastic clips which are part of the module) once it is free wiggle it and work it out patiently. It can be done just be careful and patient..

If your car has airbags, I don't recommend doing it yourself.

Hope this was helpful to someone...

 

I have the same problem with my 91. I took the dimmer switch and module out. It has two connectors to it with the variable switch. I can not find anywhere how to test the thing to see if it is causing the instrument panel and radio lights to stay on with the key off. If it is disconnected the lights don't come on, and the battery doesn't drain, but the spedo and gauges don't work either. Any help would be greatly appreciated. Thanks in advance.

Brwammack@msn.com

 

When you say the gauges and speedo don't work, are referring to the lighting or the actual gauge itself? If the gauges don't show rpms, mph and such you may have blown the fuse, I believe it is fuse #6 in the center console 5amp. The dimmer does not control the operation of the gauges. However the dimmer will cause the instrument panel to remain constantly lit if it has failed. Yours should have a green and a black connector if you search Ebay or online for one do not get one that has just the black connector, it will not work.
Good luck!

Charlie