92 sierra cimate control issues

[scotttyra5361]

I have a 92 sierra that the the climate controls have quit working, no display no nothing. I've checked the 12 volt hot, 12 volt ignition, 5 volt hot and ground and they test fine. Fuses and firewall fusible links also test fine. I've also replaced the controls with a used set purchased off e-bay. Same problem, no display no nothing. Would appreciate any and all help.
Thanks