Readers ask: Furnace flame goes out when blower comes on?

How do I know if my flame sensor is bad?

Signs Your Flame Sensor May be Failing

Here are three tell-tale signs that your sensor may be going bad: Your gas burners light but go out almost immediately. There is visible soot, dust, or rust that covers the tip of the flame sensor itself. The porcelain area of the sensor unit is cracked, chipped, or broken.

What symptoms would a furnace with a dirty flame sensor exhibit?

Signs of a bad furnace flame sensor are:

  • The furnace lights but then shuts down after a few seconds (short cycles)
  • The porcelain on the flame sensor is cracked.
  • The flame sensor is sooty or corroded.

How do you know if your furnace is short cycling?

Signs Your Furnace Is Short Cycling

  1. Thermostat Is Malfunctioning. If your thermostat is malfunctioning, it will give incorrect readings to your furnace.
  2. The Area Around the Furnace Is Hot. A furnace generates heat, so warmth around the unit is to be expected, but if it’s unusually hot near your furnace, the unit may be overheating.
  3. Short Bursts of Heat.

What does it mean when your furnace won’t stay lit?

Some common causes include issues with the thermocouple and pilot tube. The thermocouple detects the pilot light via sensors. A dirty pilot tube can also prevent the pilot from staying lit. If the pilot tube is dirty, let the furnace cool down and turn off the gas.

What happens when flame sensor goes bad?

What happens when a flame sensor goes bad? Without a flame sensor, your furnace will keep emitting gas even when there’s nothing to ignite it, resulting in hazardous gas buildup. If your flame sensor is dirty or faulty, it will automatically shut down the heating unit if it doesn’t detect a flame.

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How much should it cost to replace a flame sensor?

Similarly, flame sensors often become too dirty and malfunction, but these sensors can be fixed with a thorough cleaning. However, if it’s too far gone and you must replace the flame sensor, it will cost you anywhere from $80 – $250.

What causes flame to go out on furnace?

Possible causes:

Dirty filters, closed or blocked vents and other blockages in airflow are common causes of an overheated furnace. A bad limit switch. A direct ignition furnace has flame sensor over the burner that shut off the gas if it doesn’t sense a flame.

How do you check a flame sensor?

You can measure flame signal by putting your meter (capable of measuring micro amps) in line between the flame sensor and the wire that was connected to it (see picture). If you are reading anything under 5 uA (micro amps), it is likely that your flame sensor is dirty.

Can you bypass a flame sensor on a furnace?

Unfortunately, you cannot bypass the flame sensor and light your furnace manually, as the gas valve will not open until the flame igniter sends a signal to the control board. Attempting to manual light your furnace is very dangerous and should never be attempted.

Can a bad thermostat cause a furnace to short cycle?

A broken or poorly placed thermostat can cause short cycling. Your thermostat should not be placed directly over a heat register, as this can cause the furnace to cycle very rapidly as the thermostat quickly heats up.

What do I do if my furnace is short cycling?

If you suspect this is the reason your furnace is short cycling, it is imperative that you contact an HVAV professional to repair the unit. Restricted airflow is typically the cause of overheating which may be due to a dirty air filter or interior vents, or because roof exhaust vent is blocked.

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Is a short cycling furnace dangerous?

One furnace issue, though, should always prompt an immediate call for repair. That problem is short cycling. Short cycling doesn’t necessarily pose a threat to your health, but it can absolutely destroy the furnace if it isn’t properly addressed in time.

How much does it cost to replace a thermocouple on a furnace?

Cost to Replace a Thermocouple on a Furnace

Replacing a thermocouple costs $150 to $250, mostly due to labor time. On older models without an ignitor, it checks to make sure your pilot light is lit. If it’s not, it’ll shut the gas off.

How long should furnace flame stay on?

With all that being said, if there are no extreme factors involved, the average run time for a furnace is 10-15 minutes per cycle. Your furnace may need to run two to three times an hour to maintain your desired temperature if your home has average insulation.

How do you fix a gas fireplace that won’t stay lit?

Easy DIY Fix: Gas Fireplace Won’t Stay Lit

  1. Before You Begin: Is Your Pilot Light Lit Inside Fireplace?
  2. The Fix: Pilot Light to Gas Fireplace Won’t Stay Lit.
  3. Check Your Thermopile Output with the TH/TP Contacts.
  4. Don’t Replace Your Thermopile or Thermocouple Right Away.
  5. Cleaning the Thermopile.
  6. Re-test the Cleaned Thermopile.
  7. Replace if Cleaning Did Not Work.

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