Gas furnace doesn't light

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  #1  
Old 02-26-06, 07:34 PM
diy_tran
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Gas furnace doesn't light

I have a Heil gas furnace (model # NTG9075FGA3) and has been working fine for this winter in Northeast. Today although the furnace was still on because outside temp is low (in the high 20s) and inside temp drops. It turned out I had no heat coming out from the furnace. I went downstairs opening the furnace front panel and restarted the furnace. The blower exhaust still operating but I had no light/flame in the chamber. I also opened a small panel of this chamber and didn't see any pilot light.

I know the problem can't be the timer control board because I have a spare board and I tested but I still got no light. From the furnace spec. diagram, I really think it's the gas valve/ignition module because this is the source for the pilot light.

How do I test if the ignition module is bad ? This ignition module rated 24V. How I can check if the power switch plugging into this ignition module has power.

Thanks.
CT
 
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  #2  
Old 02-26-06, 08:29 PM
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What do you have? Spark or Hot surface ignitor? (Glows)

yes, the modular is 24 volts going to it, make sure you are getting 24 volts to it, if not, then trace back to see where the break is.
 
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Old 02-26-06, 08:57 PM
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What is the part number of the ignition control / gas valve?
You should be able to get your voltmeter probes inside the power connector from the same side that the wires enter.
 

Last edited by bolide; 02-26-06 at 09:30 PM.
  #4  
Old 02-26-06, 09:15 PM
diy_tran
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What do you have? Spark or Hot surface ignitor? (Glows)
Not sure what I have but this should be the one. HONEYWELL Q3400A1024 (Mine says Q3400A1040 but the ..1024 should fit no problem).

I'll try to test for 24v going into the ignition module. This module part # is SV9501M2726 but SV9501M2528 should replace it.

What is the part number of the control board?
The original part # is ST9120C4057 (HQ1011927HW) but my other spare board part # ST9120C5013 (HQ1170063HW) also works.

Thanks.
 
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Old 02-27-06, 04:14 AM
diy_tran
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The power switch going to this ignition module/gas value has 4 wires: orange, blue, black and white. I pretty know white wire is negative but how about the other 3 wires. How do I test them ?

Testing 24v circuit. This is a DC voltage right because AC voltage is 110v or 220v. I have the voltmeter indicating AC for 200 & 300 and DC for 1.5v & 9v. Can I test 24v circuit with this voltmeter (Greenlee DM-20) or I have to use special one ?

Thanks.
CT
 
  #6  
Old 02-27-06, 06:53 AM
diy_tran
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I see a hose coming into the ignition module, maybe it's pilot hose. So I think I have a hot surface ignitor, not a direct spark ignitor. From another thread for "furnace won't light", I will take this pilot hose and blow to see if it's got clogged.

Is ignition module smart enough to know if there is no ignition, it won't turn on the gas ? Because this module controls both gas and ignition, correct ?

BTW, I bought both ignition module SV9501M2528 and burner pilot ignitor assembly Q3400A1024 off eBay this morning so that I can the parts ready. If not, I can use as spare parts.

After work today, I will check the pilot hose for dirtiness and open the ignitor assembly to check for any unsual thing (not sure how to check except replacing if in doubt). Yesterday, the 3 wires coming out from ignition module going into the ignitor assembly doesn't look good (wire cover was stripped due to heat) to me.

Anyone has any other suggestions, please let me know. Also answer the question on 24v testing earlier if you know. Thanks.
 
  #7  
Old 02-27-06, 09:24 AM
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Ahh.. You got those "Smart Valves".....grr.... Those things are nightmare.

Lately I've seen/read people are having nothing but trouble with those valves.

I think a new one is in order.

We'll see what the other have to say.. I never had to service this type of valve.
 
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Old 02-27-06, 02:11 PM
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Smart Valve. Just replace it.
 
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Old 02-27-06, 04:31 PM
diy_tran
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Thanks again, guys. I will start troubleshooting it, I will replace the module if needed. I think I will start with the pilot ignitor assembly first, then ignition module.
 
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Old 02-27-06, 04:55 PM
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Dumb valve

If those wires are burned, you have a problem other than just the ignition system.
 
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Old 02-27-06, 05:41 PM
diy_tran
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If those wires are burned, you have a problem other than just the ignition system.
Good point. These 3 wires are small (1 going into the flame sensor, the other 2 going into the pilot burner). All 3 got burned about 3-4 inch in length. Like you said, something else may be wrong that caused such burn. I think the gas valve/ignition module may be the cause.

I have to wait for these 2 parts and go from there. Thanks.
 
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Old 02-27-06, 05:46 PM
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Burned wires

The burned wires are very unlikely caused by the smartvalve system. You could have a restriction somewhere causing a lot of heat to come back onto the wires. Worst case, the heat exchanger could be cracked. I strongly suggest you get a Heil or Tempstar dealer to look at the furnace.
 
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Old 02-27-06, 06:15 PM
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By any chance did you run the furnace with the shield removed?
 
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Old 02-27-06, 06:33 PM
diy_tran
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The burned wires are very unlikely caused by the smartvalve system.
For the last several months, I've been working on finishing my basement. I had dust in the basement due to sanding on drywall and lately I was in the processing of putting down laminate floor. This laminate type comes with attached a little cushion so that I didn't have put in separately. As I cut some of these laminate for corners, I had saw smoke and some heat generated. In the mean time, the furnace was on due to cold outside temp.

This is all I can think of as external cause. Now that I'm done with the laminate flooring.

I will go to an alternative dealer as last resource because a few months back I had a blown fuse on the fan timer control board and the dealer that I hired almost rip me off $450 for attempting replacing the board. I thought the board was bad so I ordered another one. I later traced wire diagram and found he misplaced for wire.

Thanks again.
 
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Old 02-27-06, 06:37 PM
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Ahh the smart valve. The guy that invented this was a genious. Or a parts dealer. Change the valve and the pilot assembly in one swift move.
 
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Old 02-27-06, 06:52 PM
diy_tran
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By any chance did you run the furnace with the shield removed?
I took the top panel off and ran but the result was the same. The same result happened if I also took off the bottom panel (just need to hold down the door interlock switch).
 
  #17  
Old 02-27-06, 07:04 PM
diy_tran
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Additional info,

I looked at the wire diagram a little closer and I found the blue wire of 4 wires white, orange, blue, black coming into the gas valve/ignition module comes from the pressure switch.

Any idea that any problem from this switch ?
 
  #18  
Old 02-28-06, 07:50 PM
diy_tran
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The furnace now works. I'm so excited. It turned out that the thermocouples (the 3 wires got burned) of the pilot assembly was the only problem. Because they were burned and weak. My brother was with me to help just in case I need to replace the gas valve. He even touched one of thermocouples and it broke apart. Since the wire broke, it couldn't sense the pilot for flame and therefore gas valve shut off gas.

The wires were loose and touched the chamber and that's how it got burned eventually. I think the designer should have some protection against heat. After the pilot assembly installed, I got the thermocouples tied up and ensure they don't touch any metal.

I will return the gas valve because I don't know when it will break. If it does, I can always get it. You know when you got no heat and got small kids in cold weather, you were under pressure to call the gas man. I understand my furnace a little better now from 2 separate incidents. I couldn't do without this forum and your help.
Thanks.
 
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Old 03-01-06, 04:17 AM
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Good find. Make sure you are ready to by that new valve. It's only a matter of time till that thing kicks the bucket.
 
  #20  
Old 01-05-09, 08:47 PM
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Question Pilot light not working

Yesterday, the furnace is working perfectly but when I come back today, the house is so cold at 17 degrees.I am using honeywell ignitor valve with model no. SV9501M2726. When I turned on the heater, there is no light whatsoever in the gas/burning chamber window. The fan however is working. I check the ignitor wire and it is not burned at all.

How can I turn on the pilot light? Will I light a match stick near the pilot light and turn on the furnace? The model no. of my furnace is NTGM075EGA3.

Please help.
 
  #21  
Old 01-06-09, 08:39 AM
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DO NOT light the furnace by hand!

Do you have a meter to see if you got power going to the igntior control/valve?

Chances are that gas valve needs to be replaced.
 
  #22  
Old 01-06-09, 09:21 AM
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Hey marc----

Please start a new thread to avoid confusion with the previous problem.
 
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