Problem: Fan will not come on in the “ON” position or your fan will not come on when you turn the thermostat down in the air conditioning mode.
Solution: Test to make sure you are getting 24 to 28 volts AC between the G (green) and C (com) terminals on you fan center or control board. If you aren’t getting 24 volts between G and C then you might have a thermostat problem, a thermostat wire problem or the low voltage fuse on the control board might be blown. Below we have a picture of a control board that shows the low voltage fuse. If you think you need a control board please email us with your furnace’s model number and we will be glad to try a find the right board for your furnace. Our email address is: firstname.lastname@example.org You might need a new fan center relay (if your furnace is equipped), fan sequencer or furnace control board.
A sequencer looks like the picture below. Sequencers are used most of the time in air handlers (heat pumps, electric furnaces) to control the fan blower and turn on the electric heaters in a sequence so the electric heaters to do come on all at the same time. Most of the newer air handlers have electronic circuit boards. You should have continuity between M1 and M2 when 24 volts Ac is applied to the bottom terminals. We have sequencers for sale on the following page: Please click here to go to our sequencers page: https://www.arnoldservice.com/?cat=189
- 2 Stack Sequencer
Purpose of the Fan Center Relay: The purpose of the fan center relay is to provide a low voltage control (24 Volts) to control a relay that can be used to control two-speed blower motors and auxiliary circuits in heating or cooling equipment. Many of the newer furnaces do not have fan center relays, but many of the older furnaces and some new furnaces still do. You would need to look inside your furnace to determine if you have a fan center relay. Some of the relays are attached to a junction box where the power comes into the furnace, and others are located in the blower compartment attached to the blower housing. You might not have the relay that we sell below. Many of the newer furnaces are control by electronic circuit boards. Please click here to go to our Fan Center Control Page: https://www.arnoldservice.com/white-rodgers-fan-control-center-relay-90-113/ If you think the control board is causing the fan to not come on please send us your furnace’s model number and we will try and find out which control board your furnace uses. Our email address is: email@example.com