I have a Goodman ARUF series air handler with a 10KW heat kit. The unit will not stop running and heats all the time. The thermastat is digital and is 3 years old.

Is this a 2 stage cooling system because only then you will need y2.
You can put any color you like on these terminal but it have to match up with the thermostat for example if you put black on R terminal on air handler then you have to put black on R on thermostat

if you have change the thermostat it has to have the option for electric heat the thermostat has o turn the fan on in heat mode on air handlers

The fact is, the air handler supplies the voltage, blower, and electric heat. In order for the heat pump to work correctly, the wiring from the thermostat and heat pump need to be hooked up right to the air handler. The thermostat is what tells which component to come on. If the fan stops, but the condenser keeps going, you either have a faulty fan relay on the air handler, faulty thermostat or wiring, faulty wiring at the heat pump, or the contacts on the new unit are sticking, which is highly doubtful considering it is working now. I hope I have helped you understand this a little more. Good luck and don't let them push you around, get someone that knows what they are looking at.

Heat pumps are like a refrigerator. Check the "pump" part is working properly. and is cooling one side, heating the other.

If not - maybe run out of gas (needing technical repair and refill) - or a motor fault.

if system is wired correctly sounds like the fan relay is stuck closed allowing fan to run always, need to replace control board.

Heat-Pumps can be temper mental. Sounds to me like your air handler is running on emergency heat, due to a problem with the condensing unit.You have heat strips in the air handler in case the outdoor temp. gets to cold and the heat pump cant keep you're home warm.Also, if you loose a compressor, it will go into emergency heat. If you have lost the compressor for one reason or another, lets say a locked rotor, the compressor would draw L.R.A. (Locked rotor amps) and cause the circuit breaker to trip. Check this.As for the air handler running all the time, you said you replaced the stat? When you removed the control wiring from the stat, did the fan shut off? I wish I were on site to help you, but all I can do is offer you some advice. With the power off to the air handler, go to the stat and remove the red and green wires. Turn power back on and see if it stops running. If it stops, then it sounds like the new stat is also faulty? If it continues to run, check the wiring in the air handler to make sure the red and green are not touching somewhere, and also check the control wiring on the outdoor unit for the same problem. Do you have any dogs that may have chewed into wiring? If so, check all outdoor t-stat wiring. There are so many things it could be and I hope very much I have helped you with solving this online, which can be difficult. You may also have a faulty defrost board. Try to do what I have asked of you.
Good Luck, Sincerely, shastalaker7

cross check your info plate on the outdoor unit with the curcuit breaker installed in the main panel.

You may need a "current sensing relay" to clip around the neutral wire on your blower.
Run the 120v power to the main power (the power switch- hot,neutral and ground) . Run the Hot wire through the "Current Sesing Relay" wires to the EAC unit's 120v. power input. The unit will only run when the fan is on.

Hope this helps,
Matt

If your running gas heat it's 5/8 3/8 tubing.If it's elec. heat it's 3/4 3/8 tubing. Etheirway 3/4 3/8 works for both. Use 6 wire for tstat from tstat to furnace or air handler, and you need is 2 wire from condensing unit [outside] to furnace or air handler or anything more than two.