eaerhard, How do you know when the 2nd stage is being called for? The Carrier Unit Fan ECM Control Card has small chip style yellow LEDs at each input line at the connector starting with the G (Fan) line from the thermostat, followed by the Y1 (Compressor Start) input and then the Y2 input, as well as other input signals. I assume your Climatemaster uses the same ECM card since the cabinets look similar and are probably made in the same factory. If you watch the card as the unit starts up the Fan LED will energize, then the Y1 LED, followed by the Y2 LED when you raise the thermostat setting to 2 or 3 degrees above the current house temperature, in the heating mode. This is how I can tell if the 2nd stage coil is being called for. The sound of the compressor load increase will follow if the Compressor is working properly. Not being hooked up would qualify as "not working properly".