Janitrol furnace not lighting

[ksimm]

I have an old Janitrol furnace, time for a new one, but...

 

Goodman Mfg. GUPI075-3

 

There was a similar post, but didn't seem to finish discussion..

 

The Inducive Draft Motor comes on; the pilot lights, but the system will not ignite on its own.  If I provide a small amount of airflow toward the burners, gas is immediately introduced and the system works normally.

 

My suspicion is that the draft motor is turning too slow to provide proper airflow or there is a "flow sensor" i have been unable to locate.

 

What component senses airflow to turn on the main gas supply?

 

Thank you for any help!

[jb8103]

The only air flow sensor type gizmo is a pressure switch in the induced draft airstream. That must be working or nothing else would work. You should hear the gas valve click on after a timed delay. You don't hear that?

 

On the old ignition control module will be a single LED which may or may not be used in this model. Do you see anything blinking? To test, cut power to the furnace, then power it back on while watching the LED. It should blink once.

[ksimm]

Yep. The pressure switch is connected to the induced draft motor housing and pulls vacuum from there.  I have checked this switch using a hand vacuum pump.  Without it, the signal to light the pilot never occurs.  Errr...nothing occurs...

 

Oddly, my pilot lights, and patiently awaits the roar of happy burners(i assume this is controlled by timed sequence, temperature, something...) Eventually, the pilot will extinguish(time-out safety feature, i assume) however. 

 

Although, if I provide a small amount of airflow toward the burners, pilot and thermostat; the click of a gas valve(could be a relay releasing the pilot igniter) is heard and the burners light every time...  100% of the time

 

I was assuming there is some flow sensor measuring the draw from the draft motor prior to burner ignition and that my motor might not be providing sufficient draw. Or there would be an airflow sensor gone bad...only 1 problem... I find no such sensor

 

Don't see any LED.  I think this is a pre-historic model.

 

Thanks for providing a place for me to scratch my scalp and think out loud!

[jumptrout]

There may be some corrosion or trash at the orifice spuds.

This could be reducing or re-directing gas flow.

Also clean the burner gas outlets,especially the one nearest the ignitor.

Clean them.

[jb8103]

What is it you are doing to provide this airflow?

[ksimm]

Sorry, had to move on to some other issues.  I have used a blow-dryer, breath and even waved my hand or paper to act as a fan.  Any amount of additional airflow seems to help.  I removed the motor and cleaned out the dust, re-lubed and reinstalled.  It has definitely improved my situation.  I have only needed to "assist" once or twice a day.

 

I removed the exhaust stack that leads through the roof, momentarily, to see if there could be a bird/wasp nest restricting airflow.  Didn't seem to make any difference.

 

I will clean associated parts as recommended above, but didn't want to take a chance on breaking anything as I am enjoying what heat is provided while riding out the ice storm here in N.Texas.

 

Gut feeling; the fan is worn out and not providing rated RPM/airflow.  No evidence of bearing noise, etc., but wouldn't be surprised to hear it's slow...

 

Thanks for the input!

[Budget Appliance Repair]

Pull each of the burners and make sure they are clean, especially the cross-over ports, (the part of each burner that reaches over to the adjacent burner and usually also reaches the pilot flame). 

 

If the cross-over ports are plugged up gas can't get to the pilot burner to flash across to light the burner next to pilot which then flashes across to the other burners, (waving the air around pushes the gas to the pilot were it will ignite than travel across to the other burners-most likely you will find the cross-over ports right at the pilot plugged with soot/dust buildup).

[ksimm]

OK.. Final report.

 

Got lucky. A neighbor has the same system and had the same problem last year....

 

I took the burners out and cleaned. The orifice spuds were clean; The burners had typical soot/dust, but I couldn't identify any blockages(cleaned anyway.)

 

Apparent culprit, my unit has a on demand pilot light(only comes on when needed.) Mounted to a bracket are the igniter, pilot port, and temp. sensor.  I cleaned the temp. sensor good with emory cloth, and WHAMO, this baby lights like like it's brand new.  My guess, additional airflow would wiggle the pilot flame until it found a spot on the sensor that would send an appropriate signal.  Having cleaned and lubed the motor probably provided slightly better draw "bending" the pilot flame to a "new" spot on the sensor giving slightly better results....

 

But, shine that sensor up with emory, get a beer, kick back and have a "heater lighting party!"  Pilot barely has time to light before the temp sensor recognizes it and allows the sequence to light the burners.

 

Emory cloth... The Janitrol fountain of youth!

[jb8103]

Outstanding. Well done.