The usual troubleshooting is to pull EACH 12 volt house fuse at a time and then wait and see if the 00 comes on. Once you find the fuse that when pulled stops the 00 problem you then trace and find what appliances are on that fuse and then disconnect 1 at a time to find the culprit. You could also disconnect the Power Converter 120 supply and see if the Converter is the problem. You don't need the Power Converter for the 1 hour for this test. Doug
PS, the RVP choke and filters they sell for the ZC tstat rarely fix this problem