AC amplifiers are a sensitive electronic devices. All units are tested for functionality prior to being shipped. Other componets in the Delanair MK II system could be the cause of a failure of the AC system to function properly. Failure to follow installation instructions could result in damage to the amplifier. Please contact Jag-Aire, LLC prior to attempting a return. Refunds are not gauranteed, all amplifiers shall be subject to testing upon return and refunds shall not be provided for electrically damaged amplifiers.