Units can make varied noises during heating mode (wooshing or creaking). These sounds are perfectly normal and can be louder when the unit is on a wall that is not insulated well.
When the units are in heating mode, they will periodically go through a cycle called defrost for 10-15 minutes. During defrost the unit is running in reverse with the fan turned off or on low in order to melt any ice accumulating on the outdoor unit. During this time indoor unit functionality is limited.
Not Working?
Are all of the indoor units set in the same mode ie. heating or cooling? If one unit is in heating mode while the others are in cooling mode, the unit will not operate correctly.
On a larger multi-zone system, if all of the units are turned off except for a single smaller one, it may appear that the unit is not working. Try to turn on the other units. The is usually an issue during shoulder seasons when little heat or cool is required.
Try to reset any controllers in case a timer/weekly schedule was implemented by mistake.
Try to power cycle the unit. Turn the unit off at the breaker, wait 10-15 minutes, then turn the unit back on.
Is your unit a hyper heat unit? If not, what is the outdoor temperature? If your non-hyper heat unit is not keeping up or is using too much electricity, you may want to switch over to switch over to your supplemental heating source when the outdoor temperature is around 35 degrees.
Helpful Tips
The handheld remote does not display the current room temperature. The remote can show a set temperature that is a few degrees off from the room temperature. Adjust the set point on the remote until you are comfortable. There is no thermometer in the remotes.
For the best control, be aware of what controls you have set to automatic. Familiarize yourself with the remote, especially the vane direction features to adjust where the air is blowing. Find out how you like the system to operate. The way the unit operates in auto might not be how you are most comfortable.
In both heating and cooling mode, having the fan set too low limits the capacity of the indoor units. If you need or want more heat or cool, increase the fan speed or put it into powerful mode.
Make sure you hear an audible beep from the unit when you give it a command. If you don't hear a beep then the unit did not recognize the command. Make sure you are pointing the remote, unobstructed, toward the indoor unit.
If you gave the unit a command but it isn't responding immediately, give the unit 10-15 minutes before you grow concerned. The unit might be in defrost mode and will need a few minutes before it can respond.