Im in Orchard Park. What about you?
BTW you can download Ulysse Speedometer which gives you accurate measure when driving at night. You will need GPS on your phone tho to use the app. Ive been using it a few times and works very good - best app on the market!
In terms of fuses, its worth checking all fuses to be on the safe side. The dimmer switch should also dimm the heater controls, are they off as well??
Otherwise there might be an issue with the ECU body....but need to do more research.
Also, there should be a wiring diagram on LOC or other IS websites for Gauge cluster....I will have a look once I got some more time.