Theory of Operation
The remote interface needs to send data to the control board inside of the unit. The control board processes the data and sends it back to the remote interface to display the correct temperature and RH. If you have dashes on the remote interface, there is a loss of communication to the control board. If you are trying to use the remote interface or have a remote sensor without a cable (wireless), try reestablishing the connection by moving the device closer to the unit or connecting it with the supplied cable. If the unit is connected with a cable, the power for the device comes through the cable so batteries are not required. There is an internal transformer that delivers 24 VAC to the control board. This voltage is stepped down to 7VDC by the control board and sent to the remote interface to power it. The remote interface is connected to the unit via a 4-wire communication cable with an RJ 9 connector. This plugs into the unit at a receptacle and is internally connected to the board with a smaller cable. Any one of the connections could be the reason for the loss of communication.
Troubleshooting
To start troubleshooting, if the remote interface has batteries and is connected with the cable, remove the batteries. If the screen goes blank, use a voltmeter set to VDC. Remove the cable from the remote interface and measure the voltage at pin 1 and 4 on the cable, you should measure 7DC. If you do not, check the same pins at the unit where the cable plugs into, then at the control board. If voltage is not present at the board, verify you have 24VAC from the transformer to the board on the blue and yellow wires.
If you do measure 7VDC, reinstall cable and access the settings. If you can access settings, you have communication and it’s likely that setting 30 is set to 3 so it only reads a remote sensor it can not find. You can do the same voltage measurement at the remote sensor to determine if voltage is reaching the remote sensor.
You can download the manual containing schematics for the units from our Resources and Owner Manuals page.