I have a clicking noise coming from the back of my upright fridgefreezer it still freezes my food but the clicking goes of after a while only to come back on again!

Be sure that you have the vents for the air flow in your freezer not covered up by boxes or bagged foods. It has to be able to circulate through the freezer towards the door and back to the vents if that is all clear the you may have an issue with the clicks on switch that tells it to defrost when it gets frozen up and can blow cold air through vents any more it also could be a bad element that works with the clicks o switch that tells element to come on and defrost. If that's not then you maybe low on refrigerant. .hope this helps

Check power to and from the thermostat first

is the top of the freezer full where it can breathe remove something to help it breathe

If you can hear the motor running it could be the thermostat that has gone or if there is no noise at all it could be the motor that has died, a good easy fix ( sometimes works ) is to turn the freezer off leave it for 24 hours with no power then try turning it on again.

ThanksTalkAppliance.co.uk

first of all unplug that freezer and wait for 15 mins. move it five feet from the wall. after 15mins, plug it back and kick in compressor at the same time!!!! remember plug and kick at the same time. the ckicking noise come from the starting relais. this says that the compressor has a problem. If it doesn't work ; you will have to call a service person who will replace the compressor for you.

check door seals, also check vent direction, a dial or lever in fridge, it adjust how much air goes to fridge and freezer

Here are some short videos on how to fix your problem...
Frigidaire Upright Freezer Not Freezing Repair Help 297250000

Fix freezer not freezing but still cold

Sounds like a door seal that isn't sealing all the way around. That would be my first replacement. Is the unit level back to front and side to side? Is it really full of food?

Call your local appliance parts house and get a magnetic door seal first. They aren't that expensive. But make sure you do not have the freezer overloaded, which could account for the lack of that vacuum sound.

Finally, is self defost? Even if it is, a lot of times the vent on the bottom in the back gets packed with ice. If it is, remove the food and use a hairdryer, being carefull to unplug the freezer first. Melt all that ice and empty your overflow tray at the bottom underneath.

Good luck!

This clicking noise is a bad relay.
Get it serviced before you run in to a real problem

If you heard the noise at a fairly routine rate and time it was probably the defrost timer motor. Locate it and you should be able to engage it manually. It is a plug and go part to replace. Be sure to take the old one along with the make n model # with you to the parts house!!