How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Douglas Your Own Question
Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
Type Your HVAC Question Here...
Douglas is online now
A new question is answered every 9 seconds

I have Goodman furnace (GMP 075-3). Sometimes the main burner

This answer was rated:

I have Goodman furnace (GMP 075-3). Sometimes the main burner goes out shortly after lighting.
I assume problem is flame sensor (part # XXXXX). Please advise on method to check this part,
and do you know where in Fort Worth, TX can I get that flame sensor, if necessary. Also, some of
the time, (not always), turning thermostat to a higher heat setting, and re-cycling furnace
starts gets it going. Sometimes takes several attempts. Flame Sensor???
Fortunately, you dont need a flame sensor in all likely hood.

I'll give you the 9 dollar answer here.

In a nutshell, the flame sensor is powered with a potential A/C voltage. When the burners light, electrons are passed through the flame to ground. A/C is alternating current. (back and forth). Anyway, the electrons pass to the gounded burner and back. Only part of these electrons return because the flame sensors surface is much smaller than the burners. Anyway. This A/C current is in a roundabout way rectified to a very, very light DC current. The flame sensor picks up this current and returns it to the board. There is a given range that must be returned to aknowlege a flame. To high or too low will shut the gas valve down.

This super small current is measured in microamps... 1000th of an amp.

I said all that to say this.... Clean the flame sensor. Over the course of time film, dust and silica has built up thus insulating the rod from the electrons returning. Silica as you know when heated becomes glass like. This is a poor conductor.

Take a piece of steel wool and clean the flame rod. (Not an SOS pad). If you dont have any steel wool you can use either a dry scothbrite pad or even a crispy dollar bill. You want to clean it as if you were trying to sand off a fine coat of rust.

Note I did not suggest sand paper. Sand paper contains silica and will refoul in short order onece it becomes glass again. Also sand paper is too course and will scratch the metal allowing it to catch more dirt the next time.

Anyway, power down the furnace, clean the rod as I described and turn it back on and you should be pleasently surprised. The flame rod is nothing more than a piece of metal and a ceramic insulator and unless the insulator is cracked, there is no reason to replace it.

Make sure the single wire connection is tight going into the insulator. You can pull it off and make sure the connection is clean and tight.

This should do it. If not, reply back let me know and we can go from there.

If this resolves your issue, please click accept. As always, feedback and bonuses are welcome and greatly appreciated as this is how I am paid for my time and expertise.
Douglas and 3 other HVAC Specialists are ready to help you

Related HVAC Questions