Old furnace wiring issue

Furnace is a huge old Bryant and existing thermostat is an old round honeywell with the mercury bulb. I followed what the app said for wiring based on the old thermostat but nothing happens when I switch the power back on. I checked all the connections, but I don’t really know what else to try.

I didn’t take a pic of the Wyze, but I followed the app’s directions exactly:

My reply may be of limited help, but let me toss this out there. If there is 24V AC (or anything close to it) across the Wyze C and Rc terminals the thermostat should power up. The thermostat will first power up with “Wyze” on its display.

Things to check:

If you have a multimeter, put it on the AC setting and with your HVAC system powered on, measure the voltage across your B and R wires. If it is not 24V AC, then we will need to hunt down a source of 24V AC in your system. If you do have a meter to measure with, my curiosity would next take me to measure between R and any of the other wires to see if there is 24V there. It may be that your “B” isn’t really a common (C) wire equivalent, but if your HVAC system is 24 V AC based, as most are, that should be possible to resolve.

Good luck!

Can you share a photo of the furnace wiring?

So having taken the panel off, brown and blue go to nothing…

Do you have an A/C unit outdoors or is this heat only?

Yeah a/c is outdoor. It looks like another wire set is connected to that. Yellow from the thermostat is connected (wire nut) to the red and yellow that go to a/c and the green and black to the a/c are on the furnace board’s C terminal.

You should be ok with stripping the end of the blue wire and putting it under that C terminal in the furnace as well. This should provide the wyze with the power it needs to run.

Tell the wyze you have the following wires:

C (blue)
R (red)
W1 (white)
G (green)
Y1 (yellow)

I wired the old thermostat back up for the night before I first posted, but I will give this a shot tomorrow. Thanks for your help, I’ll update after I try it.

I somehow blew the 3 amp fuse on the board, but after replacing that it’s working great.