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How do I adjust the gas pressure on my natural gas furnace? Not lighting all burners?

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Question: I have a Super Quiet 80 Achiever Series by Rudd furnace. It works great when it wants to. Intermittently it will shut down at night and we have to wake up cold in the morning. Troubleshooting reveals the first burner of the 3 always lights like it is supposed to, but the other 2 don’t always follow suit. Sometimes they light off and other times they try twice, fail, and the furnace shuts down till we reset everything and start over. The service tech came out, cleaned the ignitor, checked everything he could think of and it seemed to work well while he was here. He said we could possibly have a low gas pressure problem. I guess I’m looking for some professional input before calling him back and start the high-priced guessing game again.
I would really appreciate any input you could give me. Thanks in advance !! Joe

Answer: Hi Joe! Sorry to hear that you are having trouble with the burners not lighting all the way across sometimes. This probably occurs most often when the furnace is cold and trying to light and start. If the service tech did not already do this I would suggest that you turn the furnace and gas off, take the burners out and blow them out with compressed air and use a wire brush to clean them out on the outside. I would unscrew the gas orifices and blow them out with compressed air. I would suggest either cleaning or replacing the flame sensor while you have the burners out. If you need part numbers please send me your furnace’s model number and serial number to our email address: and I will give you the part numbers. If you are still having problems with the two burners not lighting properly I would suggest adjusting the gas pressure up (make the pressure greater) on your gas valve. I would suggest turning the adjustment screw counter-clockwise 1/4 a turn and test to see if this helps. Be ready to turn the furnace off with the power switch if the furnace does not light right away because if the gas valve is not adjusted properly it can cause delayed ignition (small explosion) and this is not good. I have seen delayed ignition blow furnace doors off! There is a really good Youtube video on how to properly adjust gas pressure on the following page:  Thanks to ACServicetech for making this great video! Your problem sounds like either dirty burners or gas pressure on the gas valve set too low. I hope you can find and fix this problem soon! Steve

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8 thoughts on “How do I adjust the gas pressure on my natural gas furnace? Not lighting all burners?

  1. I have a Miller gas furnace it’s 70,000 btu. The burners will not stay kit. It does that three times and shuts down with a tree flash code.

    1. Hi Carl! This sounds like you might have a flame sensor problem. We have a flame sensor troubleshooting page that I hope will help: I would like to suggest that you try and clean the flame sensor with steel wool or light fine sandpaper. Make sure all ground wires are good and tight and make sure that your burners are clean and the flame sensor is setting in a nice blue flame. I hope this helps you out. Please let me know if you have any other questions. Steve

  2. Steve,

    I was told that my Manifold pressure is running at 3.86″wc and gas valve is regulated for 3.5″wc. Is this small variance something to be concerned about?

    1. Hi Rod! I would not be concerned with the gas pressure unless you are having trouble with the furnace igniting properly or if the furnace sounds like a jet engine (too much gas pressure) while running. Too much gas pressure would make the furnace go off on limit and this would not be good. Your furnace should run without going off on limit. If your furnace is going off on limit then I would suggest adjusting the gas pressure down a little until you get proper smooth ignition with the furnace not going off on limit. I hope you have a great day! Steve

      1. Not only is having your furnace over fired dangerous, it’s illegal. Please call a reputable HVAC Technician to come and fix your system. Leaving it over fired could crack your heat exchanger and end up costing you far more than calling a service tech.

      2. Thanks for your advice, Adam. I did not know that it was illegal to adjust the gas pressure on a furnace. Yes, I agree that it can be very dangerous if you do not know what you are doing.

  3. I have a Ruud heat pump brand new and the outdoor fan motor will not run in air conditioner mode or in heat mode

    1. Hi Keith! So sorry to hear you are having trouble with your new Ruud heat pump. Since this is new I would suggest that you call the company out that installed the unit to troubleshoot and find out why the fan will not run because this should be under warranty. If you want to try and troubleshoot, sometimes they say this voids the warranty, but you can turn off the power to the unit and open up the control box to see if there are any loose wires or if the capacitor is swollen. I would check and make sure the contactor contacts are in good shape. If your unit has low pressure safety controls then this could cause the unit not to run at all because of a low refrigerant charge. A defective defrost control board can cause problems too. We talk about this problem on the following page: We have lots of troubleshooting questions and answers on the following page: I hope you get this taken care of soon. Steve

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