True defrost timers, clocks, fan delay switches and defrost termination switches all in stock and ready for same day shipping. Ice build up is not good. It may be because your unit isn't going into defrost mode. Replace a faulty defrost timer or fan delay before it costs you more to replace a vital refrigeration system component.< ONLY those parts identified as manufactured by True Manufacturing are OEM parts. Certain parts are not OEM products, and are not manufactured, licensed, authorized, or sold by True Manufacturing. OEM Numbers and Commonly Fits Models are used for reference only and no inference or implication beyond that should be taken or is intended. Non-OEM replacement parts are not manufactured, licensed, authorized, sponsored or endorsed by True Manufacturing.