This is a very unusual problem, but I included it in this guide because I think that it is illustrative…
if you know how the system operates, sometimes you can reason the problem through.

Once, I got a frantic call from a customer saying there’s a red glow in the bottom of the freezer in his side-by-side; he’s afraid that something’s burning. He didn’t hear the refrigerator running, but he did hear popping and hissing noises.

I rushed over to his home, and when I got there, I didn’t see any red glow. I did notice that the light didn’t work in the freezer. He said that it went out months ago, and he hadn’t gotten around to replacing it. He has had the fridge for ten years, and has never seen a red glow down there before.

I thought to myself, what could possibly be glowing red in the freezer compartment?

Bingo…the defrost heater!

I grabbed a screwdriver, reached down to the defrost timer and set it on “defrost” again. Then I reached into my tool kit for my trusty, dusty inspection mirror.

With the mirror, I showed him the red-glowing defrost heater. I explained the defrost system and why he’s never noticed a red glow before:

When the light bulb was working, the interior of the fridge was so bright that he just couldn’t see that dim red glow. And the defrost heater is only on for about 10 or 15 minutes every 6 to 8 hours. What are the odds against his opening the fridge at just the right time and seeing the fridge in a defrost cycle?

The popping and hissing sounds that he heard were the melted frost, water, hitting the red-glowing defrost heater and boiling off instantly.

I sold him a special appliance light bulb, made for cold environments. Problem solved.