I’m replacing a older programmable thermostat with Ecobee 4 which is to control a Ruud R801 HVAC unit installed last year. I have access at the thermostat to a wire (orange) that goes to the C terminal on the control board, but the Ecobee doesnt power up. Ecobee customer support I determined there is no significant voltage (<.01VAC) as measured by a multi-meter between the R and C terminals at the control board. That’s true in idle (status 0 on control board display), or heat (status H)
I’ve attached pictures of the thermostat terminal on the control board but can’t figure out what the problem is, much less fix it! The old thermostat (and humidistat) continues to work fine when Ecobee removed and re-installed. Can post other pics if I figure out how to do it on this site.