If the data of the WS-1850 is no longer visible on the indoor unit, the units have lost connection with each other. It is best to go through the following steps:

- Replace the batteries in the outdoor unit;

- If that does not help, remove the batteries from both units, place the units next to each other, put the batteries in the outdoor unit first and then in the indoor unit. Within one hour, the units will reconnect;

- If this does not help, there is a defect in the outdoor unit. If it is covered by the warranty, you can report it via www.service-hesdo.nl. If it is not covered by the guarantee, you can check on alectohome.nl whether the outside unit is still available.