"--" on the display: mode conflict (multi zone systems)

Short answer: "--" on the display means your multi zone system has a mode conflict: one indoor unit is set to COOL and another is set to HEAT. The outdoor unit can only cool or heat at one time, so set every indoor unit to the same mode and the "--" will clear.

This only happens on multi zone systems (one outdoor unit connected to several indoor units).

How to fix it

1. Check the mode on every indoor unit connected to the same outdoor unit, including rooms that aren't in use.
2. Set them all to COOL, or all to HEAT.
3. The "--" disappears and the units resume normal operation.

Avoid it in future

• Agree on one mode for the whole house each season: COOL in summer, HEAT in winter.
• To stop one room from cooling or heating, turn that indoor unit off rather than switching it to the opposite mode.

Still showing "--"?

If every indoor unit is set to the same mode and "--" is still on the display, submit a support ticket with the mode shown on each indoor unit, a photo of the display, and a photo of the model/serial label on the outdoor unit (how to find it).