Intermitten ignition problem

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  #1  
Old 01-31-05, 08:37 AM
chutan
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Intermitten ignition problem

Luxaire gas forced air furnace. It is old, maybe 10-20 years? But it is in good condition.

Problem is that intermittenly, about every other day, and always at night, the furnace will stop working. The fan turns on, (didn't check if the HSI glows), and after the click, no flame.

For the last three times when this happens, I tried multiple times to restart the system and the result is the same. So we turned off the system, and the next morning, it works as normal.

This morning, I examined as it turns on.
1. fan on 2. HSI glows 3. flame on 4. blower on
I simulated by reducing and upping the thermostat.
1. fan on 2. HSI glows 3. HSI puffs out
2nd try
1. fan on 2. HSI glows, appears to glow few seconds longer than 1st try. 3. flame on 4. blower on.

I've taken out the HSI and flame sensor, both seems to look fine.
 
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  #2  
Old 01-31-05, 08:40 AM
chutan
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I can't seem to find any LED with this system. Maybe it is too old to have diagnostic? Currently, my guess is that the gas nozzles might be weak, such that at night when usage around neighborhood is high, the gas pressure is too low to operate the furnace.

It will not hurt to clean the burner, but it is quite a pain to get it out. It is a crossbar with 3 flame nozzle type.
 
  #3  
Old 01-31-05, 09:09 AM
chutan
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More info:

MODEL: PBNU-LD10N060D
Computer(?): White Rodgers Div Emerson Electric Co 50E47-070

I've found the LED light, so far it is not lighted.

Can someone tell me where/which one is the ignition module? The HSI is directly plugged into the main board. So, the main board is the ignition module?
 
  #4  
Old 01-31-05, 11:01 AM
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This is exactly what happened to my gas furnace but its a different brand..Like I said in my post(above your post) it was the god damn ignition module that was the problem and if you live in the U.S you can maybe get this part cheap by ordering it through the internet.But, like you said in your post, when you don't have the choice and its -10F outside you have to call in the tech. www.furnaceparts.com is a good place to check for prices for these modules.The tech replaced the hot surface ignitor while he was there.
 
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Old 02-01-05, 07:58 AM
chutan
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I've found the solution to my problem, I think.

Before, I've checked to make sure that the water in the pipe is not frozen. Then I read in other thread about water collecting in pipe, then I double checked! There is one section of the pipe that is curved upwards, and some water is collected there, I drained it out and then the furnace started working!
 
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Old 02-01-05, 10:08 AM
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This curved area. make sure it pitches back towards teh furnace so the water can drain away.
 
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Old 02-01-05, 12:05 PM
chutan
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It started acting out again this afternoon.

It just cycles through HSI glows, gas valve clicks, then HSI shuts off, no flame, and repeats without going into lock out mode. No LED.

I wonder if it is possible that the HSI is not hot enough. I'll be upgrading the obsolete control module first and see if it is the problem.
 
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Old 02-01-05, 01:47 PM
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it could be possible that the HSI itself may need to be replaced.. Make sure it's lined up right so it can light the gas.
 
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Old 02-02-05, 10:36 AM
chutan
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Problem solved! Thanks for replies and valuable info from other threads.

It was just the HSI. I thought a glowing HSI means it is working, but it is not true. If your HSI does not die from crumbling, but from extended use, you'll experience intermitten ignition problems like mine.

In the past my dying HSI started glowing about 4-5 seconds right before the flame comes on, and the glow slowly builds up. I thought it was the normal process, however after installing the new HSI, it glows bright and hot instantly and about 10-5 seconds before the flame comes on. It means that the old one takes longer and longer to build up enough heat, and on the verge of dying, I experience intermitten problems, sometime it ignites, sometime it does not and sometimes it takes a few tries.

So, that's about it.
 
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Old 02-02-05, 10:39 AM
chutan
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EDIT: It means that the old one takes longer and longer to build up enough heat, eventually, it failed to generate enough heat within the warm up period determined by the module.
 
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Old 02-02-05, 01:44 PM
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Thanks for the update.
 
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