I have carrier air and heat heating on on heat unit but it has two it has two 28 volt relays that operate the heat strips. One was not working so I purchased another onewith the same ratings but it won't energize. They both say 28 volt dc but when I measured it it has 28volt ac on them. The only thing I can fiqure id their must be a rectifier in the old one. Did they make one like this and where do I find one or can I add a rectifier to the new one. Hope there is an answer out there Thanks.: