In My 93 Civic DX the dash illumination and the horn aren't working. All the fuses seem to be in tact and I know that the fuse for the instrument panel is good because the clock works. All the connectors are connected in the back of the dash, but the backlighting for the speedometer, tach, and other gauges won't light up. Also, with the horn, there seems to be a connector that I just simply can not find that isn't plugged in. The first picture is showing how the illumination for the gauges isn't working, and yes, I already checked the dimmer switch and fuse. The second picture is of that connector on the steering wheel that connects to the horn buttons.

 

all 3 of the plugs in the back of the cluster plugged in? there should be 2 long ones in each side and the srs plug, did you check all the bulbs and maybe even try putting in another cluster to see if it still does it

 

and that yellow plug is the plug for the airbag.......

 

Does it affect your climate control illumination also?
When I bought my 93 hatch I had the same problem with my gaugesand climate control. I had to replace the dimmer switch to fix it. The horn I could not tell you with out some troubleshooting.

 

It's the dimmer switch then because the climate control illumination isn't working either. Also, I thought it may have been the connector to the horn because the wires go directly to the horn buttons. Thanks!