Why does my blower motor keep running on my furnace?

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.

Why does my HVAC fan turn on by itself?





AC Unit Is Too Small Or Unable To Match Settings

A too-small HVAC system will often run to keep up with the thermostat setting, leading the fan and blower to run consistently. Additionally, if your area is facing extreme temperatures, your HVAC unit may not reach the desired temperature.

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.

Why is my furnace running when my thermostat is off?

The most common blower problem that makes your furnace run non-stop is a faulty limit switch. A limit switch is the part of your furnace that tells your system when to turn on and off. If it’s broken, your furnace won’t know when to shut off and will continue to run.

Why will a blower run on the on position and not on auto?





That’s because if the heater never warms up then the fan controller won’t automagically turn on the blower fan. Let me know what you find. Electric split unit trane the fan comes on in the on position but not in automatic. Heat or cool isn’t working on the condenser or evaporator .

Why does my blower fan keep running?

Faulty Thermostat: If both the fan and either the cooling or heating system are running unexpectedly, you may have a faulty thermostat. Broken Relay Switch or Short Circuit: If only the fan is running, there may be a broken relay switch preventing the settings you enter on the thermostat from being sent to the fan.

Why does my furnace blower not shut off?

On your thermostat, look for the fan settings. There should be two, “ON” and “AUTO.” If it seems like your furnace won’t turn off, the thermostat may be set to “ON” for the blower. Toggle the switch to “AUTO” so your furnace’s blower fan only runs during a heat cycle.

Why won’t my furnace stop running?

Step 1: Check the Thermostat



First, your temperature may be set too high. A furnace that is working hard to keep a high temperature, especially when it’s extra cold outside, can seem to run continuously. The second common thermostat problem is the fan switch. Your fan can be adjusted manually from your thermostat.

Why is my furnace blowing cold air and won’t shut off?

If it’s cold, that means that your furnace is not running but the air handler is still blowing air. If the air is hot, obviously, the furnace is on. If the air is cold, the first suspect is the thermostat. Check to make sure the fan is set to AUTO, and not to ON, which would cause it to run continuously.

Why is cold air coming out of my vents when the heat is off?

The Reason Cold Air is Coming From Your Vents When the Heat is Off. Cold air coming from vents when the heat is off is usually due to a simple setting on your thermostat. Generally, when this issue is happening, the “Fan” setting is set to “On” instead of “Auto.”

Why is cold air coming out of my vents when the heat is on in my car?



Low Coolant Level

The coolant (usually a mixture of water and antifreeze) in your engine doesn’t just work to keep the engine from overheating: It’s also the source of heat supporting the heating system. If there isn’t enough coolant in your system, the heater core will blow cold air into your car.

Why is cold air coming out of my vents when the heat is on?

This issue could be caused by an improper thermostat setting. Check that the fan blower switch is set to “auto” and not “on.” When the “auto” setting is chosen, the fan will only run during a heating cycle and won’t push air that feels cooler through the vents in between cycles.

How do you fix a furnace that blows cold air?

How To Troubleshoot Furnace Blowing Cold Air

  1. Step 1: Check Thermostat Setting. First and most importantly, make sure your thermostat is set to Heating Mode. …
  2. Step 2: Evaluate and Adjust Your Vents: …
  3. Step 3: Assess Furnace Filters and Replace Filters If They Are Dirty. …
  4. Step 4: Call An HVAC Pro.


How do I stop cold air coming through my vents?

How to Keep Cold Air Out of Your Vents

  1. Install insulation. Poor insulation causes rapid cooling of the air as it moves through your home. …
  2. Check connections. Over time, the connections in your ductwork can come loose. …
  3. Update your HVAC. Older HVAC systems are less efficient and require more upkeep than modern models.