Gas furnace keeps shutting off...driving me nuts

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Old 12-28-09, 03:32 PM
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Gas furnace keeps shutting off...driving me nuts

I have a gas furnace that is about 18 years old. It works fine most of the time. It has a electric igniter that is working. The flame sensor is also working and was recently cleaned. I also just replaced the batteries in the thermostat...twice. The issue I'm having is that it will work fine sometimes for days then it will shut off for an unknown reason. If you switch it off and back on again, either at the furnace or the thermostat, it may work fine for a few more days. But then it seems to happen again.

Can you please help?
 
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Old 12-28-09, 05:14 PM
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1) What is the make and model of the furnace? If you take the front cover off the burner compartment the model number will be listed on the rating plate.

2) Do you have a meter that measure AC volts and understand how to use it?

3) Does your furnace have a hot surface ignitor that glows white hot to light the gas? If not, what method is used to light the main burners?
 
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Old 12-28-09, 05:28 PM
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Ditto Seattle.

The fact that you can turn it off and back on indicates a safety lockout. Is there an LED in the unit blinkig a code?

Has there been construction in your area? New business and homes? All using gas heat? Could be low pressure coming in from the gas main causing a lockout on nights of high gas usage.
 
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Old 12-28-09, 08:57 PM
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Originally Posted by Jarredsdad View Post

Has there been construction in your area? New business and homes? All using gas heat? Could be low pressure coming in from the gas main causing a lockout on nights of high gas usage.

That can certainly happen, but it's quite rare.


Reminds me of one of my little triumphs when I was a new repairman for the gas utility I once worked for.

I was called out to an old large apartment building where the gas equipment kept shutting off. There had been dozens of service calls made on the building in recent months with similar complaints (not quite obvious, since each apartment was separately metered and a separate account.)

The apartments had been range only accounts for many decades, and recently converted to individual gas furnaces and water heaters.

I decided there was a gas pressure problem there, and went to the pressure control department to get a recording manometer which recorded the gas pressures for a week or so.

Yup --- the gas meter and regulator, sized for the gas range demand, was way too small for the added load.

I dropped the record off at my boss's office, and they scheduled a major upgrade of the service within a couple of days.
 
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Old 12-29-09, 03:43 PM
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Found this problem on a side job years ago. All gas subdivision the customer I had was one of the first units. Heat only kicked off on the coldest nights. They had just enough to keep the water heater running while the gas fireplace was on ever mind the furnace.

Wrote them a report to show the gas company, gas company adjusted the reg and all was well.
 
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Old 12-30-09, 07:10 PM
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Originally Posted by SeattlePioneer View Post
1) What is the make and model of the furnace? If you take the front cover off the burner compartment the model number will be listed on the rating plate.

2) Do you have a meter that measure AC volts and understand how to use it?

3) Does your furnace have a hot surface ignitor that glows white hot to light the gas? If not, what method is used to light the main burners?
1. Snyder General Comfortmaker GUG094A012TN
2. Yes
3. Yes it has a ceramic ignitor that is working. This item typically goes out each year and I've gotten pretty good at replacing them.

Hope this helps.
 
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Old 12-30-09, 07:15 PM
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Originally Posted by Jarredsdad View Post
Ditto Seattle.

The fact that you can turn it off and back on indicates a safety lockout. Is there an LED in the unit blinkig a code?

Has there been construction in your area? New business and homes? All using gas heat? Could be low pressure coming in from the gas main causing a lockout on nights of high gas usage.
LED on which unit? The furnace or the thermostat? I don't recall seeing anything on the thermostat. Where would it be located on the furnace?

No new construction in the area that I'm aware of. It's a older subdivision in Michigan built in the mid 70's. It does seem to happen more when it's colder out, but it also happens when it's not so cold (20-35F).
 
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Old 12-31-09, 04:48 PM
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Can't find your furnace on Comfort Maker site.

LED would be on a control board in the furnace. It may not have one though.
 
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Old 12-31-09, 07:35 PM
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You either have to wait and see at what stage in the sequence it is going out. Or cycle it many times to see if you can force it to act up, so you can know when it does it*. Or you could at least disconnect and reconnect spades and pin-connector jacks. And also blow out the condensate lines both ways. Make sure your filter is clean, and regsiters and dampers are open - To see if any of these things helps.

...............................................

*This does not always work though if the problem is temperature related. I have ran into such cases where people's outages only occured from set-backs over night likely because the basement(where the furnace is) got cold, and caused relay contacts or pin connectors to shrink, get stiffer, or whatever. And if by chance the furnace came on while testing, it never would fail again, until the next morning after they set the thermostat back for sleeping again.
 
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Old 12-31-09, 07:57 PM
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See if the furnace ignition control module is a model 50 A 50. If so, it has a red diagnostic light which might provide useful information.

It's probably a white plastic package with a lot of wires going to it.
 
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Old 01-01-10, 09:04 AM
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Originally Posted by SeattlePioneer View Post
See if the furnace ignition control module is a model 50 A 50. If so, it has a red diagnostic light which might provide useful information.

It's probably a white plastic package with a lot of wires going to it.
There is a Model 50E47-140 white box that has a lot of wires going to it. Does the light flash a code? If so, what do I need to look for?
 
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Old 01-01-10, 09:15 AM
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Originally Posted by ecman51` View Post
You either have to wait and see at what stage in the sequence it is going out. Or cycle it many times to see if you can force it to act up, so you can know when it does it*. Or you could at least disconnect and reconnect spades and pin-connector jacks. And also blow out the condensate lines both ways. Make sure your filter is clean, and regsiters and dampers are open - To see if any of these things helps.

...............................................

*This does not always work though if the problem is temperature related. I have ran into such cases where people's outages only occured from set-backs over night likely because the basement(where the furnace is) got cold, and caused relay contacts or pin connectors to shrink, get stiffer, or whatever. And if by chance the furnace came on while testing, it never would fail again, until the next morning after they set the thermostat back for sleeping again.
What are the spade and pin connector jacks? Are these on the back of the thermostat? I did clean the contacts on the back of the thermostat (they're multiple pins).
 
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Old 01-01-10, 12:35 PM
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Old 01-01-10, 12:39 PM
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You need a multimeter that will measure 24 VAC and DC microamps. Measuring the microamps requires a fairly good quality meter. Plus you need the skill to use that meter.

Do you have that?


Doesn't look like there's a diagnostic light on your ignition module.
 
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Old 01-01-10, 12:53 PM
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Originally Posted by SeattlePioneer View Post
You need a multimeter that will measure 24 VAC and DC microamps. Measuring the microamps requires a fairly good quality meter. Plus you need the skill to use that meter.

Do you have that?


Doesn't look like there's a diagnostic light on your ignition module.
Thanks for your help SeattlePioneer!

No, I do not have a multimeter like that.

I did do a through cleaning of the furnace today. I wanted to also see if I could find the diagnostic light. I pulled the wire to the heat sensor and the red light on the ignition module lit up...so there is one.

If it happens again I'll try and get the flashing code off of the ignition module. Is there a good website to look up the codes?

I'm leaning towards a thermostat issue rather than a furnace issue. I may also try getting a old style thermostat rather than a digital thermostat. I didn't have these issues when I had the older style thermostat.
 
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Old 01-01-10, 01:23 PM
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Control module troubleshooting.

http://www.white-rodgers.com/wrdhom/...pg0278_281.pdf

Test tstat. Jumper "R" to "W" turns on the furnace.
 
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Old 01-01-10, 01:48 PM
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Originally Posted by Jarredsdad View Post
Control module troubleshooting.

http://www.white-rodgers.com/wrdhom/...pg0278_281.pdf

Test tstat. Jumper "R" to "W" turns on the furnace.
Thank you Jarredsdad. The next time it faults I check it.
 
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Old 01-01-10, 02:26 PM
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Good, glad to help.

Helping you help You is why we are here.

Don't forget the advice from ecman, he's been in property management for many many years and knows of what he communicates.
 
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Old 01-08-10, 04:03 AM
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It did it again this morning. My Model 50E47-140 white box flashes on 1 sec then off 1 sec. What does this mean?
 
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Old 01-08-10, 01:30 PM
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Means a problem with external components or wiring.

Read the PDF I linked to in an earlier post.
 
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