I have an Aquacomfort 1250A heat pump and its showing a code dC which indicates a closed defrost sensor. The unit does not run. I opened the unit and found the sensor laying on the bottom pan. I disconnected the sensor from the terminal board, applied power and the unit started up. Shows a code of dO now the sensor is removed but it's not heating the pool, it's just in defrost mode.
I'm going to remove the sensor from the unit and test it to see if it is bad. From reading on various forums all I need to do is place the sensor (thermistor) in some ice water and check the resistance and compare that to the value at room temperature.
I Removed the sensor and tested it in cold water, in the freezer and at room temperature and it read 120 ohms in all cases. I inserted a 10K ohm resistor across the sensor terminals on the unit and when I powered it up it went into standby, I selected pool on the display and the unit started up and displayed the water temperature. Looks like I'm going to order the part, still need to find out where the sensor is placed inside.
Aquacomfort will sell me the part for $59 plus shipping but I do not know where to attach the sensor. It's $140 for the tech to come out and replace it, really to just show me where it goes.
Got a call from Aquacomfort and they have determined that my heat pump is still covered under warranty , initially I was told it was not since the unit was installed by a pool contractor. I guess that was incorrect and they are going to make good on the failure. I'll post where the sensor goes when I get it along with some resistance measurements at room, cold and freezing temperatures. From what I have read it goes on the suction (low pressure) side of the scroll pump.
Received the new part, measured the resistance at 0F, 32F, 75F and 130F degrees. Resistance was 66.5K, 26.5K, 11.6K and 3.7K respectively. The equation for the sensor is approximately Temperature = -45.7Ln(Resistance) + 187.6 or Resistance = 60.2e-0.022Temperature
Does anyone have an idea where to place the sensor?
Mike in NJ
Edited post to add more detail