Electric Heat Sequencers
simple tips to diagnose and repair sequencer problems
The sequencer is a time delay switch that turns each heating coil ON and OFF.
The sequencer also turns the blower fan ON as soon as the first heating element heats up and disconnects the fan motor when the last heating coil shuts off.
A faulty heat sequencer is often the reason for insufficient heating; some heating coils may not get turned ON anymore.
Fan and High Limit Switches:
auto or manual reset, air stream and surface mount
A disc limit switch is a thermostat that acts to a particular temperature. A furnace has a fan limit switch and a high limit switch.
The high limit switch is a safety control that interrupts the power in case of overheating.
A high limit switch OPENS on temperature rise.
A fan limit switch turns the blower motor ON once the temperature becomes warm enough. A fan switch CLOSES on temperature rise.
Furnace Fan Blower Relay:
The fan will not come ON or will not shut OFF...
The fan relay controls either a one- or two-speed blower motor in an air conditioning system for GAS or ELECTRIC units.
Most furnaces operate with two speeds; the higher rate is for cooling and the lower speed for heating. This setup requires a 6-spade relay.
Other furnace blowers operate with just one speed in heating or cooling mode – this requires a five spade relay.
Heating coils - Restring kits:
they will eventually wear out and need to be replaced.
Your electric furnace may not produce enough heat because a heating coil fails.
Since many old heating elements are no longer available or very expensive, your money-saving option may be to repair them using a restring kit.
Note: Are the high limit switch and thermal fuse OK? A liable technician will always check these critical parts too.