Understand the job you are asking it to do
A freezer holds 0°F. In a July garage at 95°F, that is a 95-degree fight, all day, every day. Units that were marginal in the kitchen fail in the garage because the workload roughly doubles.
Coils first, every spring
Garage coils collect dust, cobwebs, and shop debris far faster than kitchen coils. A spring brush-and-vacuum is the difference between a compressor that cycles and one that cooks itself by August.
Air space is not optional
Freezers pushed into a corner against hot walls cannot shed heat. Leave several inches on the sides and back, and never drape storage across the top vents.
Fill it, but do not pack it
A full freezer holds temperature better than an empty one because frozen food is thermal mass. But food stacked against the vents and fan blocks the airflow that makes the cold. Full, with gaps, is the goal.
Know the failure signs
Frost blooming on packages, the compressor never cycling off, and ice cream going soft are the early warnings. Catch them in June and the fix is usually small; ignore them and July collects.