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Jim Eastwood
Jim Eastwood, HVAC Mechanic
Category: HVAC
Satisfied Customers: 136
Experience:  I HAVE OVER 35 YEARS EXPERIENCE INSTALLING ,SERVICING, SELLING AND TROUBLESHOOTING RESIDENTIAL HVAC
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Why is my furnace pilot not staying lit?

Resolved Question:

Furnace pilot will not stay lit. I replaced the thermocouple but it still won't stay lit. Is the gas valve the next thing to suspect?

Submitted: 8 years ago.
Category: HVAC
Expert:  The Home Smithy replied 8 years ago.

You may have a defective thermocouple. You can test it if you have a DVOM (digital volt ohm meter). Set the selector to millivolts (mv) and place the probes on the exterior grounding and the end of the part that screws into the valve body (please see picture). If you place the bulb into a flame on your stove you should get about 15-20 mv. If not the thermocouple is no good.

graphic

Please post any other concerns you may have here.

Customer: replied 8 years ago.
The thermocouple is good. I know I have gas flow. I have 24 volts at the gas valve. I'm still asking what to suspect next.
Expert:  Jim Eastwood replied 8 years ago.

Where the thermocouple screws into the gas valve, are there two wires coming out of that area?

If not my next question is when you light the pilot is there a good flame hitting the thermocouple and surrounding it and are you pressing in the button firmly and holding for atleast 45 seconds?

Customer: replied 8 years ago.

There are two wires from the transformer going into the gas valve. I have 24 volts across them.

Expert:  Jim Eastwood replied 8 years ago.

I am talking about what is called a thermocouple limit and the two wires would literally come from the area where the thermocouple screw into the gas valve. Do you have those in this case?

Customer: replied 8 years ago.

Yes, the end of the thermocouple is surrounded by flame, and I've held the button all the way counter-clockwise for more than two minutes each time I tried.

No, there are no wires coming from where the thermocouple screws in.

Expert:  Jim Eastwood replied 8 years ago.

The gas valve is defective and must be changed. I have answered your question by eliminating all other possibilities.

Jim Eastwood, HVAC Mechanic
Category: HVAC
Satisfied Customers: 136
Experience: I HAVE OVER 35 YEARS EXPERIENCE INSTALLING ,SERVICING, SELLING AND TROUBLESHOOTING RESIDENTIAL HVAC
Jim Eastwood and 3 other HVAC Specialists are ready to help you
Customer: replied 8 years ago.

Approximately how much does a gas valve cost at a supply house?

Expert:  Jim Eastwood replied 8 years ago.

You can get it at a wholesale price between 50 and 100 dollars. Many suppliers are wholesale only due to liability and license issues.