After replacing batteries in both units, how to reset clock - not reading at all

What units Marc and model for more specific answare

I expect that since the unit reads the outside temperature from the remote thermostat, there is no need to "reset" the displayed number since this data is obtained live from the thermostat.

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,

take a paper clip and reset the reset button located in the battery compartment. Then, try each of the 3 channels until you get a reading in the outside temp field. Wait a good couple of minutes at each channel setting before determining the units are not pairing. Do this with the units side by side for signal acquisition, then once acquired, move the remote sensor outdoors. Hope this helps!

Simple, the instructions state that when changing the batteries on the outside temp. sensor, you must also change the batteries on the main clock unit. I had same problem when I changed the sensor batteries until I pulled the batteries from the clock and it reset fine. ( Sensor batteries first, then clock batteries. ) The clock will reset to atomic time overnight so don't worry if it doesn't read correctly at first.

I've had a similar problem with another model, an Oregon Scientific Model IWA-80055 Wireless Thermo Clock, in which when I replaced the batteries in the remote sensor, the clock would not read the temperature from the remote sensor.
I found it fairly consistent to solve this by taking a battery out of place in the clock and putting it back in.  Unfortunately this also messed up the clock's time and date.  This is also in the instructions catalogue for the device, check and see if yours gives a similar solution.

I found this solution by reading some reviews. A reviewer said it was caused by a weak backup battery that powers the display. He said to change the lithium backup battery of the main unit with the backup battery in the remote. I tried it and now it works. I can turn the unit on and off and it doesn't reset my memory. But this hasn't solved my problem with setting the alarm.

Try replacing the AA batteries in the main clock/display unit - that worked for me, then you'll probably need to press the reset button next to the AA batteries, and maybe the reset button next to the AAA batteries in the remote unit - press reset on the main unit first. My remote is now registering and the red light is flashing, but I don't know how to reset to the correct time and date - it's been scanning for a while and found nothing...

I have this clock and just finished getting it all working again. At first I kept messing around with the AAA batteries in the remote unit, finally realized there were AA batts in the back of the main clock/display unit. Replaced those, pressed the reset button next to the battery compartment. Pressed the reset button on the remote unit (it's under the back lid next to the AAA battery compartment). Little red light on the remote unit started flashing and remote temp showed on the main display. Then you have to wait for atomic time to reset itself or set the time and other display options manually - I kept messing around with the various buttons until I figured out how to do this (atomic time never reset) - start by holding down the smaller "AL" button on the top next to the big snooze/light button, use top two side buttons for up/down, use the AL button to go to next setting.

After changing the batteries on the outside unit, remove the batteries from the clock for a few minutes, then replace them. This will reset the clock to 'talk' to the transmitter.