Hi there

Im having an issue with a Carrier Hi Wall Heat Pump - Model: 42LUVHO35N

In heating the fan speed is unable to be adjusted between Auto - Low - Med - Hi.
The remote control sends the signal to change fan speed and the unit receives the signal with a recognition beep but it only stays on low fan speed.

When the unit mode is changed to Cooling, Fan, and Auto (cooling) the fan speed is able to be changed it cycles through Low - Med - Hi - and in Auto fan speed ramps up and down as required.

The unit air on/off temps are all good, refrigerant pressures are fine, cycling in and out of defrost as it should, and compressor ramping up and down as required to meet temperature set point.

A bit of back round on the unit is that it had the outdoor P.C Board replaced a few weeks ago for another issue that I am not aware of.

After discussion with the manufacturer (carrier) we came to the conclusion that it would be the Indoor P.C Board, considering that the fan speed is able to be changed in cooling and fan only and that the refrigerant side of things is working ok.

So replaced the Indoor P.C Board, and still have the same issue.

I had also checked the resistances on the Indoor Temp Sensor, and Pipe Temp sensor which were 14 Kohm at 15'c which matches up to the manufacturers values for those sensors.

Also cannot see in the literature or from advice from carrier that if the sensors were not reading correctly they would over ride the fan speed from being changed so dont think it is that.

Next step which i am doubtful will fix it is to replace those sensors and replace the indoor fan motor.

Any ideas from anyone, also could there be a setting/dip switch setting that may have been changed or needs changing from when the new outdoor P.C Board was installed?

Cheers