And they have their own thermostat. When |I bought the duplex the owner also had wired an old honeywell mercury switch thermostat as a on off overide for downstairs. I want to use thiswiring to install a 24 volt light that tells me when she is heating but want to disconnect the switch and thermostat. |It is an old 4 wire connection as follows, red, black yellow and green. How do I wire in the light and make sure that she has power to her system, thanks, Mike