1. I do agree with Benzmac the default is full heat.
2. When you say the wheel is broken do you mean it will turn and turn without stopping at full cool or full hot or actually can be pulled out? If this is ok then it should not be broken.
3. If you move the fan speed lever to the lowest setting then push the defrost button does the fan speed goes up? Also If you move the fan speed lever to the highest setting then push the any of the buttons does it change the air flow or just blow out of all vents? If not on both questions then it’s in malfunctioning mode it goes into an override function like Benzmac said.
4. Does the fan seem to go on and off intermittently? It’s actually not, it is timed in seconds. There could be five possible things wrong with the unit so five different time sequences.
5. Just count the seconds or use a stop watch, move the fan speed lever to the highest setting so you can hear it, after one clicking noise from the relay the fan will go on for XX seconds pause for four then on another same XX seconds and so on. The number of XX seconds should be the same every time and not intermittently, this number of XX seconds should also tell you what is wrong with your system.
Thai GI sends...