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Russ here. On the old C model 1 2 3 went to thermostat. On the new R model only 2 wires are needed at thermostat. Connect two of those wires to R and C at top right of EIM to R and C on thermostat.
Red to R the other White to W.
S terminals are for a dry contact on outside sensor. Normally open. Russ
My mistake you only have to use two wires. One to R and One to C. Use Purple and Grey . Disregard Blue or tape off.
What model thermostat do you have. Russ
If you have 24 volts to thermostat at R and C it should light up unless you have a bad connection or bad thermostat. Russ
I have been working on your problem off and on. The thermostat you have in not compatible with the new interface. It uses a two wire control on R and C. Where the old used a 3 wire where 1 was a data wire. 2 terminal was power wire and 3 was the common wire.
These thermostats are connected wrong all the time. All it will do if anything is blow fuse. Even if you connect the Power to 2 and 3 you will still need data terminal. Russ pi