I have a Coleman 3500-812evcon model # furnace. It has a rocker switch on top of the blower. Heat, off, cool. Its an 89 model trailer. It has a Coleman mercury bubble thermostat now two wire red and white. No switches. I have a programmable thermostat. How do I hook this up? And where do I put the rocker switch? Heat cool or off?

I have a Coleman 3500-812evcon model # furnace. It has a rocker switch on top of the blower. Heat, off, cool. Its an 89 model trailer. It has a Coleman mercury bubble thermostat now two wire red and white. No switches. I have a programmable thermostat. How do i hook this up? And where do i put the rocker switch? Heat cool or off?

Take that off your list of things to do. With it being only a two wire old style relay operated thermostat system you cannot use a regular program style thermostat unless you run new 5 wire thermostat wire AND tear out the blower control system you have now that the furnace came with from the factory. If you still plan on doing this I suggest you call a local on site HVAC contractor who has a control specialist on staff and get ready to write a good size check since there is a lot of work involved and rewiring of the furnace to do in order to make it work like you want it to and to be SAFE. Sorry but the system you have has been around since the 60's and there is no cheap and safe way to what you want to do.

I have a Coleman 3500-812evcon model # furnace. It has a rocker switch on top of the blower. Heat, off, cool. Its an 89 model trailer. It has a Coleman mercury bubble thermostat now two wire red and white. No switches. I have a programmable thermostat. How do i hook this up? And where do i put the rocker switch? Heat cool or off?

Take that off your list of things to do. With it being only a two wire old style relay operated thermostat system you cannot use a regular program style thermostat unless you run new 5 wire thermostat wire AND tear out the blower control system you have now that the furnace came with from the factory. If you still plan on doing this I suggest you call a local on site HVAC contractor who has a control specialist on staff and get ready to write a good size check since there is a lot of work involved and rewiring of the furnace to do in order to make it work like you want it to and to be SAFE. Sorry but the system you have has been around since the 60's and there is no cheap and safe way to what you want to do.
Ok thank you. Is there any type of digital thermostat I can use? I know the mercury one not accurate.