Freezer question

[IreallyKNOWiamright]

Hi
I have had a second hand freezer since the summer. It's been working quite well. However I am concerned that since last week things don't seem as 'frozen' and it has a buzzing sound so do I need to defrost it and clean it?? Or do people think it's possibly on its way out?

What is the make and model? There should be a label with that info on it somewhere. From that I would then try to find the instruction manual for it online and look at the troubleshooting section.

Do you keep this freezer inside the house - or in the garage? I ask as I found out on Friday, when the temperature drops below 10deg the freezer ceases to work !