my super clean 91 integras rear window defrost is inop. the switch didnt light up with the headlights and it had power and ground at the switch. so i replaced the switch and now it come on with the headlights. but the light that indicates its on isnt working. i looked at the wiring diagram and noticed that there was no voltage on the signal wire coming from the integrated control unit. i tested it with a test light. i know that if the switch was engaged there would be no voltage since it grounds out, but if its not engaged that test light should have lit up. im leaning toward the integrated control unit or an easy hot wire for this problem. thanks guys.

 

ICUs are a common problem on older Honda/Acura.

Do you intermittent wipers work?

Do all your warning chimes work, [lights still on, key still in ign. seat belt not on]?
If any of the above do not work it confirms you have an ICU problem, although you still may have one, [related to the rear window defog] even if all the above still work.

Before you replace the ICU, confirm rear window defog relay is working properly. 94