Model 00754W4 does not sense outside temperature..new batteries have been placed correctly in both inside and outside units..noW what do I do?

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.

my unit tells me to insert fresh batteries into the outside sending unit first. then insert new batteries into the inside receiving unit. after the outside temperature shows up, then can reset my inside unit's time, choose F or C and
switch channels. please try changing channels if your
outside temp doesn't show. you can do both units in the house then put one outside after they work properly.

Inside temp is separate from outside...no connection whatsoever. If the outside transmitter has new power and fails, it may have gotten wet inside and may be rendered useless. Replace with a new outdoor transmitter.

New batteries required, and reset .

defrost outdoor unit, quickest way put unit onto full cooling inside and it will send hot gas to outdoor unit, once unit is clear operate as required the cause of this could be a gas issue fan motor issue.a sensor not sensing correctly and not putting unit in to defrost or infact unit is far to small for area it's serving, set temperature to a manageable temperature not all the way up to the max and see how this goes, if it persists gas charge on unit should be checked to see if there is a leak. And fan should be checked to ensure correct operation.

My most consistent (best, repeatable) results with this process are to replace both sets of batteries, both in the clock and in the outside temperature sensing unit. Start by removing all batteries out of everything. Now replace the batteries in the outdoor unit, then (within 30 seconds) replace the clock batteries. The temp unit should begin communicating normally within 5 minutes (or less) and yes, you will have to reset the clock,

If your outside temperature is not showing on your clock, that may mean that the clock and the transmitter have lost their connection. To reconnect them you must first take the batteries out of both of the units for 15 minutes. First put the batteries back into the transmitter, and then the clock. Let them sit side by side inside your home. When both the indoor and outdoor temperatures show on your clock with the same reading, or within two degrees of each other, then you may put your transmitter back outside. Remember to keep the transmitter out of the direct sun in a dry place. Also keep it away from metal, which can affect the readings.

Check the batteries in the main unit. If they get low it will only show dashes for the remote sensors.

Double check the batteries to make sure they are installed correctly. If one of the batteries in the outdoor sending unit is in backwards, it will not send the outdoor data. On the indoor unit, there is typically one battery that is used for receiving the signal from the outdoor unit. If all of the batteries are in correctly but that one, you will see the display and the indoor temperature information, but the outdoor information will not be displayed.