How do I know if my furnace thermocouple is bad?

How do I know if my furnace thermocouple is bad?

If you can’t get the flame to light at all, and you’re sure the gas is on, there’s probably an obstruction in the pilot tube. If the flame lights and goes out when you release the gas control knob after holding it in for the recommended 20 to 30 seconds, that’s the sign of a thermocouple malfunction.

How much does it cost to replace a furnace thermocouple?

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.

Are gas furnace thermocouples universal?

Lead length universal gas thermocouple is designed for gas furnaces and 30 millivolt systems. It includes universal adapter fittings and is compatible with screw-in, push-in or clamp-type pilot burners.

Are all thermocouples the same?

From an operational perspective the thermocouples for a water heater are all pretty much the same. However, there are two variables, the length and the fittings used to install them, see below. A failing thermocouple will not send the correct electrical impulse and the gas valve will not release any gas.

How long do thermocouples last?

How to Tell if You Have a Bad Thermocouple? Thermocouples can last up to 10 years if properly installed and maintained, while furnaces can last 15-20 years, although either may wear out sooner in multifamily units.

Are most thermocouples interchangeable?

Watch out: thermopiles and thermocouples are not interchangeable. When replacing a temperature sensing device like a thermocouple or thermopile, you should be sure to purchase the proper part.

Can you bypass thermocouple on furnace?

Realistically, you have just disabled the thermocouple, but you can also reach in and unclip it from its holding bracket where it meets the pilot light. In most cases it will be held on with a gravity clip, but some are held on with a screw that must be removed with a small screwdriver.

What’s the difference between J and K thermocouples?

Whereas a J Type thermocouple is made up of iron and constantan, K type thermocouples are composed of a nickel/chromium alloy (chromel) and a nickel/aluminium alloy (alumel) which gives them much better protection against oxidation and acidity than the iron limbs of the Type J.

Can you replace a thermocouple with an igniter wire?

If your gas fired equipment also uses an igniter wire in addition to the thermocouple, they are often routed together and will need to be removed for thermocouple replacement. Take care not to damage the igniter wire and to reconnect it just as it was.

How do you replace a thermocouple on a gas-fired furnace?

On a gas-fired furnace you may need to remove first the furnace cover and then a flame shield. Keep any mounting screws for re-use. Remove the old thermocouple at the gas valve by unscrewing its mounting bolt from the gas valve. Typically a thermocouple connects to the bottom of a gas valve using “right-hand” threads.

Where is the thermocouple sensor located on a gas furnace?

Typically the thermocouple sensor is mounted right in the flame of the pilot light on gas fired heating equipment. Our photo (left) shows how you may spot the copper tubing of the thermocouple extending between its sensor at the pilot flame of a gas burning furnace and its connection to the gas control valve.

Who makes thermocouples for standing pilot furnaces?

Honeywell, White Rodgers, and other manufacturers make universal replacement thermocouples, usually with a 30-millivolts (mV) rating for standing-pilot furnaces.