Just a couple more notes... SSEiguy and I struggled with this one earlier:
It only affects the electronic climate controls because the manual climate controls don't have a VF display.
If you look at the troubleshooting areas:
1. The grey wire provides the rheostat signal (0-12V, dim to bright)
2. The green wire provides the headlamps on signal (0 or 12V, depending on headlamps on or off)
3. The purple and white wire provides a unique VF display dimmer signal (12V to 10V, as the rheostat is rotated from dim to bright)
Notice that a 12V signal applied to the purple'white wire will make the VF display turn completely off! I've tried it. The climate control is expecting the pulse-width modulated signal.
However, in 94, they changed the radio display from VF to a back-lit LCD display, but it appears that the climate control didn't change. Or did it? Is the climate control dimmer now self-contained, or is it simply wired differently?
I am working on getting the 94 wiring diagram, and also checking the part numbers on the 93 and 94 climate controls to see if they match.