Help with CT101 Thermostat

Ok, so I recently purchased a CT101 thermostat. I followed the directions and labeled all of the existing wires. I also took a picture of the old thermostats wiring. That said, I cannot get my system to blow cool air.

When I set it to Cool I get warm air and the house temp increases
When I set it to Heat I get warm air and the house temp increases
I swapped the W (orange) and W2 (white) wires. On Heat it produces warmer air
I moved the R wire from RH to RC (there is a jumper so it really shouldn’t matter) and I still got warm air on the Cool setting.
I remove all wires except Y and R and set it to cool and I got warm air

I hooked the old thermostat back up (was getting too hot in here) and it worked as expected, it quickly took me from 80 back down to 75.

I then wired the CT101 back up directly to the unit (I used the wall plate previously) and same behavior.

I am using only the manual heat and cool modes at this point (not auto). I have paired with ST to see if that works and no issues there (same behavior hvac wise).

Does anyone have any ideas? I did send an email to Radio Thermostat support this morning, but I"m not sure what I can reasonably expect there.

Picture of previous thermostat wiring:

Color on a wire is only a guide as the other end has to be in the right place but in my experience in thermostat wiring, these are the color codes:

Red: +24VAC. You are right. RH and RC is typically jumpered. That is because there could potentially be a 24VAC transformer from the air conditioner (RC) and one from the furnace (RH).

Blue: Common or -24VAC. Check with an voltage meter set to AC between this and red to see if you get 24VAC. It is this blue wire that allows more advanced thermostats to be run off of the power from the furnace, along with the red.

These wires get connected to the red wire for these functions:

Yellow: Air Conditioner. This trips a large relay in your condenser outside with common (blue) being the other wire. This will be connected to Red (or RC if your air conditioner has its own 24VAC transformer) to turn it on.

White: Furnace. Most furnaces go through a list of safety checks before turning on.

Green: Fan. If you run your fan constantly, this wire will be energized.

Orange is typically heat pump.

In dual stage furnaces, there is a White 1st stage (W1 or W) and White 2nd stage (W2). Always use W1 if you only have a single stage furnace. Mine could be converted to two stage and I did…it was just a jumper on the controller board. This is more common. First stage on a device is typically half-power. Second stage is full.

There are also dual stage air conditioners but they take a lot more electronics and are far less common. Y1 or Y is first stage (use it if only one stage) and Y2 is second stage.


Thanks. So any thoughts as to what might cause the heat to come on when set to Cool? The wire hooked to ‘Y’ on the old thermostat is hooked to ‘Y’ on the new one. The old one didn’t have the blue wire hooked up but I will wire that in and check with my multi-meter.

Does your condensor turn on outside?

I know my wires at my furnace had common (blue) and the yellow from the thermostat (Y) connected to the motherboard and then wires from those terminals going out to the condensor outside.

Also check for any possible shorts between yellow and white.

yes, the outside unit comes on. I read that with a heat pump the condenser comes on when the heat is running.

The wires themselves must be ok since I can hook up the old thermostat.

When measuring the voltage of the blue wire with the multimeter readings were all over the place jumping from 30ish volts to the 250 ish

I have been running tests on different configurations and at the moment I can only get either warm air on either setting (g-green w-orange, y-yellow, r-rh/rc) or cool air (g-green, w-yellow,y-orange, r-rh/rc) on either setting. This with the thermostat set to ‘heat pump’. I will try some different configurations with it set to ‘normal’ today.

Did you ever get this resolved, I am trying to install a CT101 and I have the exact same issue where I get Heat when it should be cooling. Old thermostat works properly so I know wiring is good. HELP!