The temp alarm keeps beeping, although the temperature seems fine

Check along the back and sides of the freezer for any vent-like openings that are covered or blocked by packages. There may be a sensor that's not getting air flow as it should. Although most upright freezers are now frost free, there still can be ice buildup in critical areas such as the thermal sensor or the fan. Can you tell if the fan is running?

Even if the compressor has failed, your frozen items will keep the temp down for several days. I suggest you move the frozen goods to a neighbor immediately. Meat or fish in particular quickly becomes unsafe to eat without at least refrigeration.

The manual for this unit can be found here.

this could be an issue with the defrost cycle. if ice build up accumulates the on the inside coil (evaporator), it restricts the air flow and you get alarms for being out of temp. usual signs are ice build up around the coil area. look for that first. be sure the door closes and seals too.

Good Afternoon Friend,

I understand that the temperature alarm light is on for your Frigidaire freezer, model# FFU21M8CW. This feature is designed to provide a warning of a possible malfunction. If the temperature of the food rises to a level unsafe for long-term storage, the buzzer will sound. The red light, if equipped, will also glow. The Temp Alarm feature operates on household electricity. If power fails, the alarm will not function. An ON/OFF switch allows you to deactivate the Temp Alarm when not wanted. Your freezer is shipped with the Temp Alarm in the OFF position. After your freezer has run approximately 4 hours, the red light, if equipped, will go off. Then you may activate the Temp Alarm without the alarm sounding. Press the ON switch to activate the Temp Alarm. To deactivate, press the OFF switch. If the alarm sounds, be sure freezer is properly leveled, and the door closes freely, and seals properly. If you suspect a technical malfunction, call an authorized servicer immediately. Hope this is helpful.

-Best Regards-
WP

Hi Clair, thank you for allowing me to assist you.

When the refrigerator is beeping or buzzing, it may be a warning sign of a possible malfunction or an unsafe, interior temperature. To silence the buzzer, you can depress the ALARM OFF button. However, if you have already done this, try unplugging the unit or flipping the household circuit breaker for about ten minutes.

If the alarm continues, it could possibly be experiencing a communication problem with the temperature control/board or wiring failure. I would recommend connecting with a professional appliance tech for a clear-cut diagnosis.

You could have a freon leak and needs to be looked at .

Faulty alarm.

HIGH-TEMP ALARM SWITCH (SOME MODELS)
An audible alarm will sound if the freezer temperature reaches
unsafe levels. The alarm operates on household electricity.If
the power fails, the alarm will not perform.
An ON/OFF switch allows the high temperature alarm to be
deactivated if desired. NOTE: You must open the freezer door to
view the alarm switch. The freezer is shipped with the switch in
the OFF position.After the freezer has run longenough to
lower the temperature, you may set the switch to the ON
position.
• To activate the alarm, set the switch to the ON position.
• To deactivate the alarm, set the switch to the OFF position

i got this from the freezer manual from Kenmore hope this was helpful

Hello twins49
Welcome to Fixya,

You said, your Frigidaire freezer 17 cu. ft. , it keeps buzzing or peeping
The alarm may be malfunctioning or it may be warning you of low temperature.
You can go to any hard ware store and buy a refrigerator thermometer and ask them if it can go into a freezer too!It can, But ask anyway!

If it is cold enough then it is a faulty alarm going off.

Your freezer may be equipped with an alarm.
Here is some information that may help you find it and turn it off if you wish

Temp Alarm (audible only or audible with warning light)
This feature is designed to provide a warning of possible malfunction. If the
temperature of the food rises to a level unsafe for long-term storage, the buzzer will
sound. The red light will also glow on models so equipped. The Temp Alarm feature
operates on household electricity. If power fails, the alarm will not perform. An ON/
OFF switch allows you to deactivate the Temp Alarm when not wanted. The freezer
is shipped with Temp Alarm in the OFF position. After freezer has run approximately
4 hours, the red light, if equipped, will go off. Then you may activate the Temp Alarm
without the alarm sounding.
Press the ON switch to activate the Temp Alarm. To deactivate, press the OFF switch.
If the alarm sounds, be sure freezer is properly leveled, and the door closes freely, and
seals properly. If you suspect a technical malfunction, call an authorized servicer
immediately.

Let me no what you find.
Huuum
Please remember to leave a rating before you leave

is it possible the door has not been closed at some point?
If so they can build up with ice in the evaporator which the defrost system cannot handle....Try a manual defrost.
Depending on where the unit is installed high ambient temperature can drop the internal temp enough to set the alarm off though they will still freeze sufficiently