Nathans88stepside

Hey there I have an 88 c1500 with the old push button radio and heater/ a.c. control, and within the past few months the the heater and ac control panel has given out on me. It worked when I first put it in but after awhile it slowly started to flicker on and off and now it is completely shut off with no led dispayls at all. I have checked fuses and all are good. I have power coming from one of the pins in the connecting plug to the unit itself. I'm not sure if I should be getting power through them all but when I test each individual pin I hear some clicking from behind the dash but only have power light on at one point like I mentioned. I have switched several of the units themselves ( think I've tried 4 now) and known of them seem to light up what so ever. At this point I'm stuck and any advice would be appreciated thanks guys. - nathan