[SOLVED] Boot loop of death when turning heat on

Natural gas furnace with forced air. The furnace controls the fan.
Every time I turn the heat on I hear a click from the unit, but the thermostat will turn off - power cycle, and will just go into loop trying to turn the heat on and then reset. Getting it to stop is a hassle.

Deleted and re-setup the thermostat but didn’t help. Cooling work ok and so is fan. Old thermostat had jumper between RC-RH.

Any ideas? thank you

Sounds like there’s a short somewhere. Can you post pictures of the wiring on both the thermostat and the furnace board?

Connection at furnace


Gas Ignitor and valve (No control board)

you have a green wire on C at the wyze tstat but a blue wire attached to G on the C wire adapter. where is the green wire on the furnace side of the wiring?

The green/blue are one. whoever did the wiring probably connected 2 different sets, with one end green and the other blue. it was confusing first, but i checked them with a continuity tester.

there may be a splice somewhere

I was confused by the blue wire as well. It could be that somewhere around where the blue wire turns green there is some short going on between those two and other wires.

I assume, since you are using the C-adapter, the old thermostat was using batteries. If that is the case then it would not be affected by this short circuit. I’m not sure how much of an ordeal it would be, but I think the safest thing is to install a new wire.

I think so too. I tried to find the connection point but so far I couldn’t find it.

You are correct about the batteries. Looks like I will have to replace the line.

make sure u run at least a 5 conductor cable, so u can get rid of the adapter


Update: Replaced the wires, this time got 5: R,G,B,W,Y.
Re-setup the Thermostat, but still getting the same issue - as it tries to turn the heat on, the thermostat resets.

Since I didn’t have the Blue (common) before, I connected the new wire to the bare metal of the furnace. Is that OK ? it gives me the 24V as expected from the R and C wires. Should other wires also give me 24V ?

maybe @speadie can help

Need a better image of this area

Specifically, make the tags readable and allow me to see which wire bundles are feeding what wire nuts.

Hi, I had the same issue when I switched to an Ecobee. The cause was that the high temperature limit switch on my furnace was tripping and cutting power to the thermostat. My old thermostat had a battery backup so I never knew this had been happening the whole time. I had a tech come out and turn down the gas pressure and the furnace is no longer overheating and the reboot loop is gone. Not sure if that applies in your situation but thought I would throw that out there.

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This the new 5-wire setup

Thank you. I assume you are talking about this:

It controls the fan, so that it will kick only when the furnace reaches the temperature, right? That’s how it was with the old thermostat.

From what I can tell, it looks like the wire marked Y1 is the one that goes to the outside unit along with the red wire. The wire coming from the Thermostat should probably be connected to the Y1 terminal on the furnace instead, along with that wire.

Honestly, I am not sure. Mine looks very different with a fixed temperature threshold printed on it. Yours looks like it’s configurable. My understanding is that the limit switch shuts everything down when the furnace gets too hot, but may keep the fan running to cool things off.

You are correct about the Y1 wire and red one going outside. You might see that red wire is connected to 2 white ones at the back.

So let me understand: the Y wire from the thermostat should connect to the Y1 wire going outside, but I’m not sure I understand which other wire to connect to it.