Heil NUGK 867 model furnace problem

[transferguy]

Posted By: lionround

I am getting no gas to the pilot; therefore, no gas to the burners. I have replaced the exhaust blower motor and capacitor because the old one was not running and was hot to the touch. I replaced the high limit switch last year. Ideas?

[transferguy]

posted by: Mr T

Does your inducer spin up? It will not attempt to light the pilot until it detects proper combustion airflow.

If your inducer does not spin up and you replaced a bad one, the relay on the board may have taken a hit, especially with a hot motor/high current draws.

If your furnace has error an LED(s)/display, it should indicate a code as to what device detected a problem (*NOT* what the problem is). Look up this code in your manual or troubleshooting guide.

[transferguy]

Posted By: lionround

Yes, the inducer spins up. This a 2001 model so I don't believe there are any LEDs on the control board.

[transferguy]

posted by: Mr T

Diagnostic indicators existed back then. You need to check if you have them. Otherwise, without troubleshooting knowledge and tools, you will just be guessing. Guessing can get expensive.

If the inducer spins up and nothing else happens, it could be in the inducer or ignition systems.

Possible issues in the inducer system: failing inducer (cant spin at correct speed), failing or blocked pressure switch (detects if it's moving air correctly), blocked intake or exhaust (bird/bee nest?), damaged relay on the main board (not allowing enough current to flow due to arcing of the relay contacts..not very likely but possible)

Possible ignition issues: failed ignitor (if hot surface, but no pilot used in this system), arc not reaching pilot gas (you said pilot isn't lighting, so you may have this type of ignition) due to bent bracket or weak spark, dirty flame sensor (very common and can cause unusual symptoms), ignitor or pilot light not reaching gas due to dirty burner or bent bracket.

On a side note. You said you had a high-limit switch fail. A properly functioning furnace wont reach high limit and the switches do not normally fail at lower temps. If your furnace is reaching high-limit, you have other issues and really should have it looked at. Let the tech know about the recent failures. Make sure all your registers are open and all the returns and registers are not blocked. Make sure the filters are changed, dont use above MERV8 unless your system is designed for it. They restrict airflow. Overheating can really shorten a furance's life

[transferguy]

Posted By: lionround

Mr. T thanks for your help on this. I am wondering if I should smell some gas. Since the pilot isn't lighting, shouldn't there be some gas present that I could smell? I am leaning toward the ignitor.

Does the air pressure switch prevent the gas from flowing to the pilot?

[transferguy]

posted by: Mr T

If the proper combustion airflow is not detected by the pressure switch, then the furnace will not attempt to light. It's a safety device.

[transferguy]

Posted By: lionround

Well, I think I have found the problem. The ignitor is for some unknown reason completely closed up. There is no gas coming out of the pilot. It looks like it was welded shut, which really makes no sense, but there it is.

[transferguy]

posted by: suemarkp

If you have an ignitor, you don't have a pilot. The ignitor should light the burner directly each time it needs to be fired up.

Mark
Kent, W

[transferguy]

posted by: Mr T

If it sounds like a stove lighting or a tazer (lots of clicking) before anything lights, then you have spark ignition (more or less a spark plug). .these systems are not common anymore, but they do light a pilot at the start of the cycle. Once the pilot lights, the thermocouple opens the main gas valve. There MIGHT be a flame sensor that opens the main gas valve in some setups. This system is also known as a intermittent pilot since it doesnt stay lit 24/7

If there's nothing at all, then all of a sudden the burners just light, then you have a hot surface type igntion with a ignitor (think a light bulb without the glass globe). This lights the burner directly.

If you do in fact have a spark igniton and you are talking about the 'sparker' being closed up (shorted out) or the pilot tube being pinched off then something bumped it.. It could have been you when you were checking the furnace out.. If that's the case, the original problem may still exist......and return. (usually on the coldest day of the year)

[transferguy]

posted by: lionround

Yes, it is a spark ignition. There is a clicking but no fire. I diagnosed it by taking the tube off the pilot side of the gas valve and blowing through it. It was plugged. I thought at first it was the tube itself, but then I took the tube out completely and it was clear. That is when I took the ignitor assembly off and saw that the gas tube portion was blocked. It appears from my research that this was the LP version, not the Natural Gas version. Nat gas burns hotter than LP.