Furnace Only Works After Reset: 9 Problem+Fix

The reset button in a furnace is a quick way to solve a short-term problem in the furnace. But, if you always need to reset the furnace to start it, there might be some deeper issues with the unit. 

Dirty filters, faulty sensors, and controllers, closed dampers, low fuel, corrosion, and aging are common reasons behind a furnace starting only after a reset. To solve it, clean the filters, replace the controller, check the dampers and gas level, and look for error codes in the thermostat.

In this article, we will go through these problems in detail with some solutions for why the furnace starts only after resetting. These problems are mostly seen in oil furnaces but apply to other furnace types. 

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Why does a furnace start only after resetting?

You will sometimes face a situation where the furnace will start, but it won’t fire. 

Once you flip the power switch off and turn on the furnace again, the unit will work fine. 

You will either face this problem very few times or frequently. 

It is the furnace’s way of telling that the unit is facing some issues. 

You need to detect it and solve it quickly. 

A furnace is an important part of the house during the winter. 

It helps warm the surrounding air and spread it throughout the house. 

If there is any serious issue, you must fix it. 

If your furnace starts only after you reset it, the problem can increase and progress to something serious over time. 

Here are a few reasons behind a furnace starting only after resetting:

1) The control board is bad.

A furnace starting only after resetting could be due to the control board failure. 

Maybe the board is in bad condition, so the unit keeps shutting down and does not start after resetting. 

When you shut off the main power to reset your furnace again, it clears the error code and allows the furnace to work great, but temporarily. 

If you delay analyzing what is wrong with the control board, the problem will persist and progress over time. 

So, it is better to hire a professional and ask for help to fix the controller soon. 

2) Dirty air filters

Some error codes occur due to dirty air filters. 

As a result, your furnace won’t start unless you reset it. 

A furnace does not turn on if the air filter is very dirty. 

It blocks the airflow and does not allow the furnace to spread the warm air. 

Some furnaces have an in-built system of shutting off if the airflow gets blocked due to dirty air filters. 

Since resetting will clear the error, your furnace will work great after you reset it. 

But the furnace won’t start over time even if you reset it. 

Over time, the furnace will stop producing warm air and release yellow or even flames instead of blue. 

So, you need to change the filter. 

Shut down the main and open the furnace’s external panel. 

Gently remove the filter and try seeing through it for darkness and discoloration.

If you cannot see anything through the filter, it is time to replace it. 

If you buy a washable filter, you do not have to change it frequently. 

You must wash it with water, dry it, and install it back. 

While installing the filter back, install it in the airflow’s direction to let in enough air. 

3) Faulty or dirty flame sensor

When you turn on the furnace, the burner will turn on, but it will go out after a few seconds. 

Resetting will temporarily clear the error, so your furnace will start working fine like before. 

Consider checking the flame sensor once. 

There could be dust and debris that covers the end part of the sensor. Cleaning the flame sensor can fix the problem. 

Sometimes, it could be because the sensor casing got cracked. 

In that case, you have to replace the sensor. 

Replacing the sensor is a low-cost fix. 

You can handle it yourself if you are fine with working on the furnace. 

Otherwise, hire a professional. 

To clean or replace the sensor:

  • Open the furnace access cover. 
  • Based on the model, you need to unscrew some screws or bolts. 
  • You will find the sensor outside the burner assembly. It looks like a small rod with porcelain surrounding the end connected to the burner. 
  • Some sensors are straight, and some are bent at a 45 or 90-degree angle. 
  • Disconnect the wires leading to the sensor and control board and loosen the screw to remove the sensor.
  • Take an emery cloth and gently remove the dust and debris from the sensor. Clean the remaining with a stiff brush or steel wool.
  • If it requires replacement, replace a new one in the same way as the old one. 
  • Reconnect the wires to the sensor and control box, fix the burner assembly, and screw back the furnace cover. 
  • Start the furnace to see if it is working or not. 

The sensors will cost less than $20. 

If you consult a professional team from HVAC, expect the total payment to be around $75 to $250. 

4) Too many closed dampers

Sometimes, people close some furnace dampers if they have a two-story house. 

Keeping the upstairs dampers open will make the upstairs very hot. 

However, closing too many dampers will harm the unit. 

A furnace is designed to keep heat registers and dampers wide open to spread enough warm air throughout the house. 

If you close too many dampers in the furnace, it will block the airflow, further burning out the motor. 

As a result, the furnace will require resetting 1-2 times to start working. 

If the problem persists, your furnace will constantly shut off.

If the furnace runs despite the closed dampers, the airflow will increase in the ducts, creating a whistling noise.

So, make sure that the dampers are open for adequate airflow. 

However, you can partially close or open the dampers according to the temperature of your house. 

5) Cracked furnace heat exchanger

A heat exchanger maintains the separation of the combustion process and oxygen for proper breathing. 

It stops carbon monoxide intoxication. 

If the heat exchanger is cracked, unburnt gasses like carbon monoxide, sulfur dioxide, and nitrous oxide will enter your house and intoxicate it.

When a crack occurs, the furnace will not start at first. 

But, after resetting, it may work fine, but only for some days. 

Over time, the furnace will keep tripping off, and you must reset it multiple times. 

You can understand that the heat exchanger has cracked when you smell bad odors, see discolored metal, or find a change in the flame color. 

A cracked heat exchanger will reduce the furnace’s efficiency, consume more fuel, and increase energy bills. 

To prevent the crack:

  • Keep the vents and air inlets open and clean. Remove the blocks like furniture for proper airflow. 
  • Change the air filter when dirty.
  • Check the whole unit once a year to look for cracks and other damages. Even if you take proper care, there will be cracks over time. 

You need to replace the exchanger if you find cracks. Please consult a professional to do it. 

6) Insufficient fuel levels

If your furnace does not have enough fuel, it will turn off at the start but start working after you reset it once or multiple times.

Though the furnace will work after resetting, it may turn off again after some time. 

The furnace turning off immediately after a start is a sign that there is not enough fuel left in the unit. 

Check the oil storage tank and refill it immediately if only a little is left. 

To prevent this problem, contact your local company for regular service delivery. 

The oil requirement frequency depends on your tank’s size and the furnace’s usage. 

For fair tracking, you can track the oil and check the daily at the same time. 

Most of the tanks use 4 gallons of oil per day. 

You may need 125 gallons of oil per month. If you have 250 gallons, fill the tank up every 2 months. 

7) Clogged fuel line

A clogged fuel line will encourage constant resetting. 

The furnace may trip out of safety due to the clogged line. 

After that, it will start working fine if you reset it once. 

But over time, you might have to reset it multiple times.

So, you need to check the fuel lines for your furnace

Check the valves in the fuel line to confirm that they are open. 

If they are closed, it means the valve directions are wrong. 

Turn the valve to open the gas valves. 

You will hear the flow from the fuel line again. 

Turn off the furnace’s main line before opening the gas valves. 

Otherwise, there could be potential fuel problems. 

8) A problem with the thermostat

The thermostat accesses modern furnaces. 

A thermostat guides you about the timing of turning the furnace on or off. 

So, if the thermostat fails to communicate with your furnace, your furnace reset button will start popping up. 

It can be tempting to press the reset button, but you must do it only once. 

So, before you flip the switch to the ‘On’ position, consider checking the thermostat to see if it is showing any error. 

9) Corrosion or aging

For older systems, corrosion and aging is a common thing. 

A furnace lasts for 10 to 20 years. 

The older systems may not show any aging signs, but they will trip off often. 

So, restart your furnace by resetting it. 

If your old system has evident rust signs, it is time to replace your furnace. 

Corroded metals will not only trip your furnace, but they can also lead to severe accidents. 

If your new system shows signs of corrosion, the reason is moisture deposit. 

Check for leakages and patch them. Call an expert to deal with it. 

How many times can I reset the furnace system?

Whenever a furnace detects a problem or danger, it will trip off. 

This system is new in most of the recent furnace models. 

When the furnace trips off, the reset button pops up. 

When you see the button, you can hardly resist pressing it. 

Resetting is an easy way to fix most problems in the unit. 

When the reset button pops out, the unit thinks resetting is the best solution. 

You need to reset your furnace once. 

If the problem is solved and never happens again, it is fine. 

But, if you always need to reset your furnace once every time you start the unit, the problem is severe, which the reset button cannot handle. 

Do not reset your furnace more than twice. 

If you press the reset button multiple times, it will constantly hit the ignition area with oil and make it ignite. 

If the oil does not ignite now, pressing the reset button multiple times will create a bigger flame when the furnace suddenly turns on.

How to reset a furnace?

Resetting a furnace is one of the easiest ways to troubleshoot most furnace problems. 

A furnace requires resetting mostly in winter because it works overtime during the winter and sometimes becomes very hot. 

Resetting the furnace will stop the unit and restart it again, preventing a popped circuit breaker. 

Resetting a furnace would be better than resetting the breaker. 

Here are the simple steps to reset a furnace:

  • Find out the furnace power switch near the unit and turn it off. 
  • If you do not find any switch, turn off the breaker. 
  • The reset button might pop out. Press it for a few seconds until it clicks.
  • Wait for 10 seconds. 
  • Turn the switch or the breaker back to the ‘on’ position and check if the furnace is running well. 

If you have a gas furnace:

  • Turn off the gas control setting to turn off the pilot light. 
  • Set the thermostat to the lowest setting. 
  • If the furnace has an electric ignition, switch off the circuit connected to the furnace. 
  • Close the main gas supply, but keep the pilot gas supply line open. 
  • Relight the pilot light with a matchstick, lighter, or piezoelectric spark ignition. 
  • Turn on the main power and gas supply back. 
  • Press the reset button for 30 seconds and release it. 
  • Your furnace will start. After that, adjust the thermostat settings. 

What is short cycling?

When the heater turns off before it reaches the full heat cycle, it is called short cycling. 

It occurs when your furnace overheats, and turning off is the furnace’s way to indicate something is wrong. 

Overheating can occur due to low airflow or a large-sized heater. 

Different houses will need different sizes of furnaces. 

An oversized furnace can heat your room and shut off as a safety measure if the heating increases. 

In that case, you will have to restart your furnace. 

Your furnace will frequently shut off if you don’t replace it. 

Final thoughts

Though resetting a furnace is a good way to solve maximum problems, constant resetting indicates a deeper issue. 

When you see that you have to reset the furnace every time you start, it is time to analyze the real cause behind it and solve it. 

You can either solve it yourself or hire a professional. 

The common problems behind a furnace working only after reset are a bad control board, dirty air filters, closed dampers, cracked heat exchangers, insufficient fuel, clogged fuel lines, thermostat issues, corrosion, and aging.

The reset button popping can seem tempting to press but reset the furnace only once or twice. 

If your furnace still trips off, consult this article to find out why. If you can’t, ask for help from the HVAC team. 

Reference: Wikipedia.

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Arthur Smith

Howdy! I am Arthur Smith, an electrical engineer who is extremely passionate about electronics. I have lived in different parts of the US and currently reside in Wisconsin. I am one of those rare children who knew what he wanted to study and do in life right from the start. I was a curious child who wanted to know how switches work and how the AC works, and I would always observe my dad whenever he would handle the wires and fix things around the house. I currently work as an electrical engineer at a reputed company and write for this blog. And I read loads of books or play video games in my free time.

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