Is the "remote sensor" the unit that is mounted outside? If so, then the thermometer is the unit that is inside the residence?

Place your remote temperature sensor and the inside unit together for about an hour to see if they both read the same or if there is a large difference in the temperatures.

Dashes on the outside temperature reading may indicate that the inside unit is not receiving a signal from the remote. Change the batteries on the remote or change the location of the inside and/or outside units so that they can receive a strong signal between each other.

Your smartphone temperature may be coming from a location that is not near your home. They are often from a weather service. Where is your local temperature sensor located? Is it in the sun? Is it on the south side of the house, or another location where the sun or an air conditioner or other heat source may affect the accuracy of the reading? Try to locate your outside sensor in a shaded location with plenty of ventilation, and away from heat sources.

Question edited for clarity. Full 'make model (what it is)'.

Did you put batteries in both units and in the right order, sensor first?

Step 1: Insert 2 fresh AA, batteries into the TX29U-IT sensor according to the polarity marked in the battery compartment.

Step 2: Insert 2 fresh AAA, Alkaline batteries into the wireless thermometer according to the polarity markings. Step 3: After 5 minutes place sensor outside in a shaded location.

https://www.lacrossetechnology.com/products/WS-9160U-IT#support

Retired unit so no further warranty or parts.

You can still get one on Amazon

La Crosse Technology WS-9160U-IT Digital Thermometer ...

Amazon.ca https://www.amazon.ca > Technology-WS-9160U-Digita...

Digital thermometer with wireless remote and clock; Remote sensor transmits from up to 330 feet; records daily high and low temperatures; Receives weather ...
Rating: 4.4 · ‎ 7,970 reviews · ‎ $31.50 · ‎ In stock
..

likely in your configuring set up menu. Either you are telling it that it's the wrong sensor or haven't found it yet.

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

Alkaline batteries will not work below freezing in the outside temperature sensor. Buy Lithium batteries for the outside sensor unit alkaline are okay for the inside unit.

Try taking the inside unit outside as close to the transmitting unit as possible for three minutes. The signal might lock on to the setting you want to receive.

You can get the manual at: http://www.manualslib.com/manual/257219/Hunter-44665.html

Normally these thermostats read remote temperatures but do not use them for control. The external remote sensor is normally put outside in our area yeilding an inside out side thermometer.

You have to push some buttons to tell the MAIN unit to scan, then put battery into the REMOTE, set channel, and hit reset through a little hole. And the MAIN should see it.

Bring the outdoor sensor inside. Take batteries out of both the sensor and the main unit. Wait 10 minutes. Put batteries in remote sensor. Then put batteries in main unit. Don't touch any of the buttons for 10 minutes or until the outdoor temperature is displayed. If still not displayed after 10 minutes then try again.

My outside display stopped working, but the inside display still worked. I found that one of the two batteries in the inside unit was almost all the way dead. Once I replaced both batteries the outside display worked. I also checked the batteries in the outside unit. After all batteries were installed, I pushed the small button that is inside the battery compartment on the outdoor unit. It's now working perfect..

Wireless Digital Thermometer GE5805WS4
Instruction Manual

Buttons and Functions
Button Function
Front of unit:
Min/Max...........displays Min or Max temps recorded
CH(Channel)......changes displayed channel
(hold 3 sec to erase)
Clear................clears memory in Min/max display
Back of unit:
C/F....................Toggle between Celsius
or Fahrenheit temperature display
Scroll.................Remote Channel Scrolling ON/OFF

INSTALLING BATTERIES
IMPORTANT:Read the section SETTING UP THE THERMOMETER before installing the batteries for the first time.

1.Remove the rear cover of thermometer. Install 2 new AA batteries. Replace battery cover.
2.Loosen 4 screws on rear battery cover of the Remote Sensor and slide battery cover off.
3.Install 2 new AA batteries .
4.After batteries are installed, the remote sensor will begin transmitting and automatically register to the Thermometer
(within range) after several minutes. However, you can also press the small button in the battery compartment (labeled Tx) to register the Remote Sensor to the Thermometer immediately
5.Replace battery cover and tighten 4 battery screws. Make ure that the battery cover is fully on and tightened to assure a watertight seal.

SETTING UP THE THERMOMETER
The thermometer can monitor up to two different Remote Sensors on two separate channels. Add-on remote sensors can be purchased separately and are compatible with the GE Wireless Thermometer/Clock (model GE5805WS4) as well as this unit. When first installing, always insert batteries into the Thermometer first, then into the Remote Sensor.
The thermometer uses random security code technology-it will learn the random code of the first Remote Sensor it detects and log in as channel 1. Channel 2 will register in the same way. NOTE: Registered channels will be erased when the batteries of the Thermometer or Remote Sensor are removed. When replacing batteries for a Remote Sensor, remember to clear the corresponding channel of the Thermometer in this way:

1.Remove batteries from the remote sensor (step 2 of installing batterie)
2.Select the channel that you would like to clear by pressing the CH button on the Thermometer until this channel number is displayed.
3.Hold the CH button for 3 seconds to clear the channel
4.Follow steps 3-5

MOUNTING THE REMOTE SENSOR AND THERMOMETER
Remote Sensor is suitable for outdoor mounting (watertight) at a range up to 100 feet from the Thermometer. HOWEVER, HE UNIT SHOULD NOT BE MOUNTED IN A POSITiON WHERE IT WILL BE SUBMERSED IN WATER, OR EXPOSED TO DIRECT SUNLIGHT, OR NEAR OTHER SOURCES OF HEAT OR COLD (I won't bother typing the rest) except for:

LOW Battery icon for the sensor will show up on either the
ch 1 or ch 2 display depending on which sensor is losing battery power.

Battery life 6 months
Temp Range Therm 32 to 122 deg F
Remote Sensor -58 to 158 deg F *
*Alkaline batteries can freeze temporarily at temps below -4 deg F. In this condition, the Remote Sensor cannot accurately transmit temp info to the Thermometer. This limits the effective minimum temp fo the Remote Sensor to -4 deg F

Operational Range....>50ft(and up to 100ft)(less interferances)

RF Channel ....refresh to "---" if no signal received in 60 minutes