Refrigerator Woes: Too Hot!

[rhino]

We have a Whirlpool side-by-side refrigerator/freezer that is about 20 years old, give or take a year or two. It's given good service for the most part, but now it's acting badly.

Recently the freezer compartment is allowing frozen things to melt regardless of where the temp was set. This evening I found that the outside on the freezer side was hot ... not warm, but almost too hot to touch.

I turned it off and my father and I commenced to brushing and vacuuming the condenser coils on the bottom (which hadn't been done in ... recent memory). I also vacuumed the crap out of the back side where it's vented in the lower corner for fan to suck air.

Now it's not quite as warm to the touch, but it's still warmer than I think it should be. The inside is feeling a little cooler, but not like it should be.

I can hear the condenser humming, but I can't tell (by listening) if the fan is running or not.

Given the age, is it time for a new unit? Or is there potentially an obvious and simple fix? I'm guessing it could be the fan or a variety of other things.

Any ideas how I could help it limp along until we get a new fridge or get this one repaired? I'm thinking of a fan blowing air from the outside under the fridge across the condenser coils, but we don't have a fan for some odd reason!

Advice and suggestions welcome! THANKS!