Another thermostat installation question--can someone look at my wiring and offer suggestions?

Similar issue to others–installed Wyze thermostat and getting clicking when I connect the device. I am attaching photos of my old thermostat-furnace-Wyze connections. I’d appreciate any insight!

Also does anyone have tips for removing a wire from a port to make a change or remove the device completely if I need to reconnect the old thermostat? I tried moving the little plastic lever back to vertical and pulling wire back out, but the plastic lever broke off and the wire got stuck.

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To remove wires, press down on the lever and pull on the wire.

so first thing i am seeing with the wires is that you probably have a splice somewhere near the furnace, the wires in the wall are a different color than the wires in the furnace… See if you can find that splice and check to make sure the C wire is actually connected. Also seeing that the wires in the wall are pretty badly deteriorated and that you stripped them back and crimped new jumpers on them, so that’s good… Do you by chance have a multimeter?

Thank you! So, at the furnace there are wires in G (red), R (red), W (purple), Y (grey). The next upstream node, G(red1) splices to green, R(red2) splices to red, W(purple) splices to white1, and Y(grey) splices to white2.

Y(grey) connects to white3 which is part of an 18/2 wire
The 18/2 wire also has a red wire which is spliced with a blue wire from the 18/4 wire

Next node upstream:
The 18/2 wire: red splices to red; white splices to white
The 18/4 wire: blue splices to orange, white splices to white, green splices to green, red splices to black (black wire goes to SafeTswitch)

Hope that helps.

And I do have a multimeter

hmm. this is some unusual wiring.

there’s no C wire attached at the furnace,
if you look under this electrical tape do you see a blue wire?

so far your wiring diagram is looking like this:

So, as you can see, the C wire that you have at the thermostat doesn’t appear to be connected to anything. I’d be willing to bet that with your multimeter set to AC volts you wont find anything around the 24V that your thermostat requires between R and C.
If you find a blue wire under that electrical tape, it is possible that that is the other end of the blue wire you have at your thermostat, and you might just need to jumper that back to the C terminal on your furnace in order to get the thermostat to power up.

If you dont find a blue wire, you would need to use the C adapter, which would need to be put in at this junction

so the wiring diagram would look like this:

You will need a chunk of wire between the c wire from the c adapter and the c terminal on the furnace board. note that with the C adapter installed, your green wire is connected to C on the thermostat, not G.
Remember to tell the thermostat app that your old thermostat uses the following wires if you do this: Rc, G, Y, W

Problem solved! I did find a blue wire, but connecting that didn’t work. So I attached the C Adapter as you suggested above and it worked Thank you so much for your help!

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I’ve always wondered why furnace/thermostat wiring is so complicated. With how cheap microprocessors are now, why not build in some smarts into furnaces, run some power to the furnace, and a simple signalling circuit to a thermostat? Legacy devices?

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If I ever move up north, I should take a course in furnace ownership and cold-weather survival.

There are some furnaces that do this with a serial connection, but they all tend to use proprietary signalling, and their thermostats are absurdly expensive and lacking in features, so if you want to use a third party thermostat, you have to use the legacy connections. The simplicity of a legacy system lies in the fact that the thermostat is really only a temperature and humididty controlled switch, so in case of emergency (failed thermostat, dead batteries, etc), you can just jumper R to W for heat, or R to G and Y for cooling. I’ve used a paper clip in place of a failed thermostat to keep a house from freezing before.

The complexity in thermostat wiring generally comes from installers taking shortcuts, and people not wanting to run new wires for the newer systems that need more signalling wires, and random splices to replace damaged wires along the way.

It’s expensive because there’s no industry standard. Define some furnace protocols around mqtt and let every manufacturer follow that standard and see how simple it can get. It might even lead to a wireless thermostat.