I have 2 wires going to the thermostat but I need 5 wires for heat/ac/fan. I cannot pull a new wire. What do you guys use to make this work?
Cheap option - Fast-Stat 5000,
http://www.fast-stat.net
Expensive option - Honeywell Prestige IAQ with Interface Module,
https://customer.honeywell.com/en-US/Pages/Category.aspx?cat=HonECC+Catalog&category=Prestige+2-Wire+IAQ+Comfort+System
Excellent. Thanks for the quick reply!