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: Purchase a new fan center relay or fan sequencer. A sequencer looks like the picture below. We have sequencers for sale
Purpose of the Fan Center Relay: The purpose of the fan center relay is to provide low voltage control (24 Volts) of line voltage circuits (110 volts) and 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.
1. Make sure that your furnace switch is “ON” the furnace blower compartment door is on and secure. Move the lever on the thermostat to the “ON” position. The fan blower should come on. If it doesn’t then you probably have loose or burnt wires in behind the relay or you may need a new fan relay or circuit board.
2. Many times wires are either loose or burnt behind the fan center relay. First make sure your furnace power is turned off. Remove the fan center relay and inspect it for loose or burnt wires. Repair wires and reinstall fan center relay. Turn the power to the furnace back “ON.” Hopefully you have fixed the problem!
3. With the furnace on use a multimeter set to AC Volts, to test between terminals “R” and “C.” You should get a voltage reading of approximately 24 volts AC. If you do not get any voltage reading, your low voltage transformer might need replacing or you are not getting high voltage to power the transformer. Sometimes furnace manufacturer’s connect the furnaces transformer through the limit control so if your furnace over heats or if the limit is stuck open then you will not get power to the transformer. There are quiet a few variables that can occur to cause furnace problems. I believe I have covered the main problems. If you have the fan center relay like we sell below the low voltage transformer is combined with the fan relay. Below we have pictures of the fan center relay with an opportunity for you to purchase. This relay will work on motors up to 3/4 horse power.
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