Clicking thermostat with no screen 27.2 volts

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1

Hey,

I have read a few forms on here to try and solve this issue but nothing seems to work.
I had an old Honeywell 2 wire thermostat originally connected. With a loose green wire on the cable not connected to anything.
I (think) I found a common terminal in my boiler. I wired the green wire to the green in by the thermostat and connected it to the C terminal on the thermo.
When I plug it is, there is constant clicking with no screen on.

In the schematic my thermostats which just controls heat is connect to P5
P9s middle screw has 27v from terminal ro ground which is what I used.

Please let me know how I can fix this thanks.

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IMG_11913024×4032 2.45 MB

2

hmm …
try p5-7 as Rc and p9-3 as C, with p5-9 as W1

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While you do have 27V from p9-2 to p5-9, it is through the thermostat controlled relay coil, so it cannot pass enough current to power the thermostat.

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2 Likes
3

I’m not getting any voltage under that 3rd screw.
I did switch it and now I no longer get ticketing. I don’t get anything.

4

Did you verify that your Rc wire is attached to the wire that comes from p5-7?

You will need to swap the wires that you previously had on Rc and W1 in order to use p9-3 as your C wire.