I have a Dometic Brisk II Duo-Therm purchased around 2018 in my Keystone rv. When it gets too cold and freeze mode is triggered, the compressor is supposed to shut off and the fan is supposed to go into high mode until the system thaws out. But, mine shuts the compressor and the fan off. Then it takes hours for it to thaw out because the fan is not running. Even if I put the fan in manual high or low, when freeze mode is triggered, the fan will shut off.
I have purchased a new thermistor and placed it closer to the area that freezes first (bottom left) and placed it further into the coil so it detects the freeze sooner. That helped reduce the freeze to thaw cycle, but did not get the fan to come on.
I then cut the leads on the old thermistor and connected a variable resistor in place of the thermistor. When I set the resistance to around 15k ohms, the compressor shuts off and the fan goes to high as it should. While it is in freeze mode, I can slide the resistor down to around 10k and the AC will kick out of freeze mode and go back to normal operation.
Even more interesting, with the thermistor plugged in, when the unit goes into freeze mode and the compressor and fan shut off, I can unplug the thermistor and plug in my resistor (set above 15k) and the fan will come on high (the compressor will stay off). I can then plug the thermistor back in, and the fan will shut off. Plug the resistor back in, and the fan will go to high again. I can keep swapping them back and forth until the thermistor's resistance drops below 10k (that kicks the computer out of freeze mode). Each time I use the resistor, the fan works as it should. Each time I use the thermistor, the fan shuts off.
I took apart the old thermistor. It is a simple thermistor only, no capacitor, no diode, no resistor, or anything else in series or parallel.
I have taken the circuit board out and checked it closely for cracks and burns. Cleaned with a small brush and put it back in. No change. All 120 volt AC and 12 volt DC connections have been replaced. The thermostat has been swapped with my other AC unit also.
I have never been able to get the freeze mode to work right with a thermistor, but it works every time when I trick it with a variable resistor.
It doesn't sound to me like there is a physical problem with the circuit board. I think it is a bug in the software. The part number on the box containing the circuit board is 3313191.000
Has anyone else ran into this problem?
Can anyone say they know their Brisk II Duo-Therm performs freeze mode correctly??? If so what is your circuit board part number?
Thanks!