Could be a faulty defrost thermostat if it has one? If defrost stat is fitted the evaporator coils have to reach a set temperature before the timer will kick in. If you can get me make and model i can have a look at the set up?
I replaced the defrost thermostat as it packed up. The heater kicks in now ok. But in diagnosing the fault, I poked inside the timer. Its a continuous timer with plastic pinions. It works sometimes, but sometimes sticks on the defrost. (I believe twice a day?)
They’re pretty fragile little things but quite cheap to replace, they can be stripped but I always loose something!!! Silicon spray believe it or not can actually make the cogs bind very badly depending on what they’re made of, evil wd40 and then blown out with some compressed air once its moving again. If its in a pretty clean environment a little light grease or air tool oil is better. A lot of these parts are quite generic and easily obtained.
I’ll have a look and see what type/model of timer is fitted but youve probably already done that? You could just bypass the timer, after re-reading, your timer initiates the defrost cycle. So removing it wont stop the freezer working, it will just stop the defrost cycle.
Sorry @Earwig I’m easily confused!!! (And didnt read the posts correctly!) My bad!!! Didnt spot they were two seperate posts
But it might not be compressor, might be start/run relay or condensor fan if fitted? Also temp probe, temp controller?
To be fair 12+ years for a domesic fridge or freezer is pretty good going!!!
Quick check, you’ll have two pipes going into compressor, one thin one thick. Thick is suction and thin is discharge, thick should be cold, thin should be hot. On a cheapish freezer if this is not the case then the reed valves are possibly passing in compressor. Can go more in depth if you need or want to?