gas furnace not working

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Old 02-10-11, 09:05 PM
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gas furnace not working

My janitrol gas furnace isn't working. The draft inducer motor starts, then the hot surface ignitor glows for about 10 seconds and goes dull. It glows again after a minute and again goes dull. After a third cycle, the inducer motor shuts down. Also, if I run my fan by flipping the switch to on (versus auto), the fan runs fine.

Any help is much appreciated!
 
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Old 02-10-11, 09:17 PM
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Before the ignitor shuts down do you hear a click from the gas valve? On the control board there shoudl be a light (usually red) which will blink several times, pause, then repeat the blink sequence. If yours does, how many blinks are you getting? Do you have a voltmeter & know how to use it? Model of the furnace would be helpful.
 
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Old 02-10-11, 09:23 PM
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Originally Posted by Grady View Post
Before the ignitor shuts down do you hear a click from the gas valve? On the control board there shoudl be a light (usually red) which will blink several times, pause, then repeat the blink sequence. If yours does, how many blinks are you getting? Do you have a voltmeter & know how to use it? Model of the furnace would be helpful.
No click when the ignitor shuts down. The red light on the control board is lighted solid throughout the process. I'll check the model in a minute...
 
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Old 02-10-11, 09:45 PM
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I was wrong about the click. Every time the ignitor kicks in AND shuts down, there is a click. Also, the model# is GMPN060-3. While I was there, I also checked "venter pressure switch" (the rubber tube). It's clean as a whistle.

Thanks!
 
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Old 02-10-11, 10:03 PM
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The click you hear is likely the ignitor relay. You need a voltmeter to check to see if you are getting power (24 volts ac) to the gas valve. You will need to monitor the voltage (or lack of voltage) from the time the ignitor starts until it goes dull. I hate to leave you with no heat but it's midnite here & I have to get up at 5:00. We can pick this back up tomorrow evening. Maybe SeattlePioneer is still up & online. Being a west coaster he might be able to jump in here & help but I have to get some shuteye.
 
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Old 02-10-11, 10:08 PM
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Sure thing. I don't have a multimeter, so that will give me time to get one. I truely appreciate the concern and help.
 
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Old 02-10-11, 11:36 PM
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Heh, heh! I might have been able to help but snowdrift has already tucked in for the night!

The late shift is on duty.

Doesn't a ten second warm up period for the HSI seem a bit short?


Still, I think Grady has the right idea. Check to see if 24 VAC to the gas valve is being switched on. If so, for how many seconds?

If that voltage is on, you should be getting gas from the main burners. Is that happening? Check to be sure all the gas valve are turned on.
 
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Old 02-11-11, 04:49 AM
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S/P, Good catch on the warm up time. Yes it does seem short. I would expect more like 15-20(?) seconds. Glad the late shift was here to bail me out.
 
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Old 02-11-11, 03:14 PM
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Hi Grady/SP, I timed the events:

Time from "click" to start ignitor to the "click" to stop ignitor = 13-14 seconds (this is when the ignitor is glowing)

Time from "click" to stop ignitor to the "click" to start ignitor = 27-28 seconds (this is when the ignitor is dull)

I will check the voltage when wife gets home. Trying to get the kids to flip the switches ain't quite working...

Thanks!
 
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Old 02-11-11, 07:21 PM
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Any voltages yet snowdrift? Any other gas appliances in the house & if so, are they working ok?
 
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Old 02-12-11, 03:03 PM
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Yes, we have a separate gas furnace for the upstairs and it's working fine.

Finally got the voltages, and they don't look too promising. The wires are so close together (plugged into the gas valve) that I had to unplug one of them. So I measured the voltage by touching one wire plugged into the value and another hanging outside. When the ignitor starts the voltage went to 0.20VAC, when the ignitor switched off it jumped to 0.34VAC and then quickly went to 0.17VAC, where it stays until the ignitor kicks in again.
 
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Old 02-13-11, 09:01 AM
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Progress. The next step is finding out where we are losing voltage. What is the model # of the furnace? I may have a wiring diagram which will help in tracing the wiring.
 
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Old 02-13-11, 01:59 PM
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The model is Janitrol GMPN060-3.
 
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Old 02-13-11, 06:17 PM
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One of the terminals on the gas valve should have a pink wire. That pink wire goes thru several switches. Set your meter for continuity & check each of those switches. They should all be closed (having continuity thru them).
If they all check closed, find the red wire which goes thru the limits. They should also read closed. Let us know what you find.
 
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Old 02-16-11, 09:20 PM
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Guys, I just might have found the culprit. One of the switches shows no ohm reading (shows 0.L). So where do I buy one of these suckers? Does Depot/Lowes carry them?

Thanks!
 
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Old 02-16-11, 10:57 PM
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A switch for what? What reads are you getting and how are you testing it?


Usually, you want to use a voltmeter to measure the voltage from chassis ground to each side of a switch to see what is happening.
 
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Old 02-17-11, 09:23 AM
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Grady said this: "...That pink wire goes thru several switches. Set your meter for continuity & check each of those switches. They should all be closed (having continuity thru them)."

That's exactly what I did. I set my multimeter on ohm/continuity check and followed the wire/s. Each does go through multiple "switches". When I touched the 2 sides on the first few, they showed a reading of 0 (continuity or no resistance). Then I came upon one switch where the reading showed discontinuity.

This switch is made by Klixon. I've tried to look it up online, but couldn't find one that looked exactly like it. I will look some more.
 
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Old 02-17-11, 01:24 PM
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Often the most reliable way to get a suitable part is to buy it from a distributor for your furnace, providing them with the model and serial number from the rating plate in the furnace.
 
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Old 02-18-11, 06:20 AM
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I pulled out the switch, which is pretty small, and then realized that the center of this small cylindrical part has a tiny button that can be pushed in, like a switch. I did that, and checked continuity. It was restored! So I put the switch back into the furnace, fired it up, and everything worked great. Now the draft inducer motor started, then the hot surface ignitor glowed and then the gas burners fired.

The heater worked for one cycle until the room temp reached what I had set on the thermostat. When the heater cut off, it is not starting up again. So this switch has tripped, again.

Any idea what causes these switches to trip? Time to throw in the towel?
 
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Old 02-18-11, 08:26 PM
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That switch is a manual reset limit. If there are several of them, switch two around. If the problem stays with the switch, the switch is bad. If it stays with the position, I'd first try increasing the fan speed since I don't think you can change the amount of time the fan stays on. If that doesn't work, naturally after checking the filter, looking for blocked or restricted vents (suppy & return), & checking for a dirty fan, it might be time to call a pro. That funace has a history of cracking heat exchangers.
 
 

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