adaptive defrost board

The entire batch of these boards, including the replacements were manufactured in the late 90s - early 2000s using substandard electrolytic capacitors from some overseas manufacturer. These capacitors were also used and caused problems in many other products such as PCs. If your defrost board has failed, replacing these capacitors with high quality units may solve the problem. One symptom is that the relay starts chattering/buzzing (DO NOT use tantalum capacitors which can emit poisonous fumes when they fail.) Also, the relay may have failed due to the capacitor problem. Replacement relays are available from companies such as NTE.