Ruud furnace burners not igniting. The pilot light is on, and the fans turn on but no heat?

if the pilot is on with no main gas it sounds like its the thermocouple at the pilot.

if it isn't hot enough it will not allow the main gas valve to open.

sometimes the thermocouple will get covered with the white powder residue from the gas burning on it and insulates the thermo against the heat of the pilot. Clean off the thermo with steel wool or fine sandpaper.

also clean the pilot burner, it too gets clogged with the powder residue and will not be a big enough flame to heat the thermo.

check and make sure the pilot is burning right on the thermo.

if these look good its probably a bad thermo. Theres usually one small bolt and nut that holds it on the pilot light bracket.

they usually just plug into the gas valve, take it with you to the furnace parts store, they are interchangeable with other models.

they'll fix you up.

HI Mike, it seems that you've got gas coming through the valve as evidenced by the pilot staying lit. So the problem is on the demand side of the furnace, which could be one of 3 issues. From least to most expensive here they are:

1. The Flame sensor is carbon coated, clean it off with steel wool. This part has a ceramic sleeve over a wire and sits in a bracket where the pilot heats it. If the pilot lights but the burners don't kick on, this is probably the culprit.

2. The thermocouple, an aluminum tube that runs back to the gas valve from the burner may be bad.

3. Pressure Switch is bad, have found this on Ruud furnaces.

4. The gas valve is failing to open when demand is called for which leads to number 5.

5. The "brain" or ignition module control board is not working correctly, there is sometimes a reset on the board that you can use, most have to be replaced,

Good Luck!

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some how what you are saying does not make sense to me.The part about turning the furnace off for ten minutes then the burners work for a spell? Typically the temp. drops in the room with the thermostat and the thermostat responds and sends a signal to the gas valve to open. The gas valve will open IF the pilot light is on. The main burner is now lite and will burn until the temperature in the furnace plenum reaches a set temp. once this temp is reached the fan then starts and pushes air to the rooms and satisfies the thermostat setting. Once the setting is reached the gas valve closes and the fan continues to run until the plenum cools down to the correct set point then the fan stops and only the pilot remains on. Are you certain the main burner is not coming on even for a short spell? If your "air filter " was plugged then the fan could not remove the heat from the plenum and the high temp limit switch would shut off the main gas valve until the plenum cooled and then it would open again. The high temp. plenum limit switch may hae failed not allowing the gas valve to open, I just don't see how it can run after being off for 10 minutes or so. Have someone watch the burner as you raise the the thermostat setting and see what takes place. Good hunting!

This problem is indicating that the computer/electronics that control the burner gas valve is not functioning properly. The fact that you power off and back on to make it work leads me to believe that is component is the problem. If you have some experience with electronic circuit board replacement, you can most likely find and purchase the circuit board online and install it yourself. However, this is a bit risky if you don't have the experience necessary to test, troubleshoot and resolve these types of electo-mechanical issues. I would suggest you call a trusted AC/Heat service company. If you feel that are two high, get another company to come out and give a second opinion. You can expect to pay about $75 for the diagnostic call-out, $75 for repair trip and anywhere from $100 to $500 for the circuit board if it needs replacing. Good luck and I hope this helps.

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RE:

Ruud furnace burners not igniting. The pilot light is on, and the fans turn on but no heat?

Hi, I have a 14 year old Ruud UGDG-075AUER. Just today it stopped giving heat. The burners won't kick on.

The fans turn on, both of them.

The pilot light is on and stays on.

The switch is set to, "on" like its supposed to be.

The air filter is dirty but shouldn't affect its...

Ruud Furnace

It is easy to diagnose the Problem But would need to be in front of unit with a Voltage meter Start by Checking Voltage at gas valve if you Do not have 24 Volts to the gas valve then Problem is not in gas valve.. Just go from there and trace back the Circuit to the gas valve make sure the Flame Sensor is Clean

But on the newer Models if the flame sensor is not working then the Pilot will not stay lit if the Combustion blower is running and pilot lit then it is not a Thermostat Issue as it is calling for heat Can you smell a strong odor of Natural Gas? First thing you need to determine is if you have Voltage to gas valve if you do have 24 volts to valve then valve is bad

I have seen in some cases where they ran a copper line to the gas valve natural gas Corrodes Copper and it will flake apart and stop up the Screen that is on the Inlet to the Valve and that will Block gas Flow Other than that unless I was in front of Unit it is hard to diagnose an electrical problem

Just reset the limit switch inside the blower cage . Strange place to put them but Ruud puts them there . You have to pull the blower out to get to it . Track the two wires that go back there it will lead you to it .

You might have a dirty flame sensor. If you know where to find it, use some fine steel wool to clean the sensor and try it again. It's worth a shot.

sounds like you have done all that's possible,

at this point i would call a repair man