1989 Cherokee Instrument cluster illumination

The three bulbs behind the instrument cluster that provide illumination have quit working. The other bulbs in that area (blinker indicator, high-beam indicator) are still functional. Fuse and bulbs themselves not the problem. I saw a reference to an "illumination relay" in the repair manual. Could this be the problem, and if so, where is it located?

There is no relay in there that I know of. Power is from a fusible link (for most all of the light functions), through the park fuse (I think), through the headlight switch, through a variable resistor (on the rear of the headlight switch) (dimmer)(this is often were the problem is), through the instr lps fuse, then to the instrument lights, the ash tray light, the radio lights (sometimes) and the transfer and tranny shifter background lights and some others.

yea its a common problem for that dimmer. Ive replaced mine allready about 4k miles ago. They just dont have a shelf life.

I discovered tonight that the parking light/dash light dimmer fuse was blown, and continues to blow replacement fuses. Would that be caused by a faulty headlight/dash dimmer knob?

Possible - it depends on how the thing fails. It can fail to ground (short out,) fail to "always bright" (short across,) or just quit working (open circuit.)

Replacement of the switch is fairly easy, and requires a philips screwdriver (to remove the lower dash fascia,) a thin flathead screwdriver (to disengage the locking tabs on the connector,) a wide flathead screwdriver (to remove/install the retaining bushing at the front of the switch,) and your finger (to hit the lock button to pull the shaft out.) I usually have them done well inside a half-hour (I've done a few...)

It should be readily available in the aftermarket - I think it's a GM switch. Check the Borg-Warner line for a replacement.

5-90

just make sure you undo the battery connections, I did a headlight switch in a sundance once and I was in a hurry. Shocked the hell out of me, car went from a fully charged battery to dead, and it burnt my finger.