Why does my blower motor keep turning on and off?

If your blower is constantly turning on/off when the furnace isn’t heating… …you most likely have a bad fan limit switch. Your furnace fan limit switch is basically a control system that determines when the furnace blower assembly should turn on and off.

What can cause the blower to come back on for a short time after cycling off?

Usually this is a problem of residual heat in the furnace heat exchanger rising into and re-heating the plenum air, causing the fan limit switch to turn the fan back on to try to cool down the system by extending the heat exchanger temperature purge cycle time.

How do I stop my AC from short cycling?

How To Stop and Prevent Short-Cycling

  1. Check your air filter. Believe it or not, a clogged air filter can cause a wide variety of air conditioning issues. …
  2. Check your thermostat placement. …
  3. Check your air conditioner’s refrigerant levels. …
  4. Replace the low-pressure control switch. …
  5. Check the compressor.

What causes a AC unit to short cycle?

Frozen evaporator coils are a common cause of short cycling. Sometimes, air conditioners freeze up when they’re running while it’s too cold outside, usually at night. In other cases, freezing may be caused by a dirty filter or a mechanical problem. Shut your system down, allow it to thaw completely, then run it again.

What is a short cycle HVAC?

The phrase short-cycling itself comes from what people in the HVAC field call an air conditioner or heat pump system that becomes stuck in the start-up cycle, and turns on and off rapidly, without ever completing a full cooling cycle.

Why does AC fan keep turning off?

The air filter is too dirty

If your air filter becomes too dirty, it can restrict airflow and cause your evaporator coils to freeze over – causing the unit to shut off prematurely. If changing your air filter doesn’t resolve the issue, contact an HVAC technician.

Where is the fan limit switch located?

Your fan limit switch is located inside the furnace panel cover, usually near the upper right corner. The fan limit switch is responsible for turning the blower on and off at the appropriate times.

How do you test a fan limit switch?

Fan Limit Swith Checkout Procedure

  1. Disconnect the fan motor circuit at the L4064.
  2. Turn on power and set thermostat to call for heat. …
  3. Turn off power, recconnect the fan switch, turn on power and again set thermostat to call for heat.
  4. Fan should come on when plenum temperature has reached fan-on setting.

Where is the fan limit switch?

While it can differ slightly from one furnace manufacturer to the next, you can find the high limit switch by removing the furnace cabinet cover. The fan limit switch sits on a mounting plate and has a long temperature sensor that extends into the furnace plenum: an air chamber that fills with air from the blower fan.

What is considered short cycling?

Short cycling has nothing to do with time between normal on-off cycles. Short cycle occurs when unit is rapidly turned off then back on within less than 3 minutes at t-stat or power interruptions such as during lightning storms.

Can thermostat cause AC to short cycle?

Your thermostat could also cause the HVAC system to cycle on and off rapidly, a process known as short cycling. Your furnace or central air conditioner spends a good amount of energy simply turning on and off, which is why you want yours to run for at least 15 minutes at a time before shutting off.

How do I know if my thermostat is short cycling?

Room and Thermostat Difference

If the temperature reading of the room steadily increases during the heating cycle but stops short of the set temperature—and does so continuously—then the furnace is short cycling.

How do I know if my AC is short cycling?

Air conditioner short cycling in minutes: If your air conditioner turns off and back on at intervals of less than five minutes it is short cycling and needs repair. If your air conditioner turns on and off at intervals of less than ten minutes it is probably short cycling and also deserves a service call.

Why does my AC turn on and off every few seconds?

Your air conditioner may be short cycling because it is repeatedly starting up then overheating (and shutting down) due to a bad compressor, dirty filters, dirty coils, low refrigerant, or frozen coils. An overcharged system will cause liquid Freon to get into your compressor and cause it to malfunction.