LaurieD
Oct 7, 2005, 04:22 AM
When I use the Auto feature on the heater it won't come on but when I put it on Fan it runs just fine.
What's causing this?
labman
Oct 7, 2005, 05:52 AM
The fan is controlled by relays and limit switches. Many furnaces use separate relays for heat and continuos fan. Continuous fan also bypasses the limit switch. If the one relay is bad and the other Ok, or the limit switch is bad, the furnace would only run continuos fan. The relays are on a control board on newer furnaces. The limit switch is inside the furnace near the burner. When my furnace did that a few years ago, I had to buy a new control board, over $300 just for the part. Labor could be another $100. On top of the increased prices for energy, ouch.