Furnance keeps switching off


  #1  
Old 11-08-03, 05:06 PM
Paladyr
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Furnance keeps switching off

Hello there! This is my first question, hopefully it's an easy one .

Our gas furnace, which is only a few years old, turns on for about 5 minutes and then shuts off. The current temp is 68F, but we have it set to 71F. The heat will turn on and it won't budge past 68, and never gets up to 71F. This is the first really cold day we have seen (30F) so this is the first time we have noticed.

I went downstairs and watched the furnace while it was on. It runs the fan for a minute and then the 3 burners turn on. They stay on for about 20 seconds and then shut off. The fan runs for another minute or so and then the burners come back on for 20 seconds. A minute later, the furnace turns off, and the temp is still 68F.

Any ideas on what could be wrong? I have tried using "run program" on the thermostat with it set to be 71 on Sat. as well as using the hold temperature set to 71. Thanks for the help!
 
  #2  
Old 11-08-03, 05:18 PM
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You haven't said much about the fan.. fan stays on the whole time while the burner is cycling on and off??

Make/model of your furance please, so we know what way to go...


Filters clean??
 
  #3  
Old 11-08-03, 05:24 PM
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Question heat

Is the air filter clean? what fan runs?Did you put this tstat on? ED
 

Last edited by Ed Imeduc; 11-08-03 at 05:36 PM.
  #4  
Old 11-08-03, 05:47 PM
Paladyr
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Well for the first time today it seems to be working. It is a janitrol... didn't see a model number anywhere though. It is REALLY low on efficiency.

When you say the filters, do you mean the air filters in the vents? We replace those once a month I believe.

Since it is working now, is it safe to forget about this or might this be a problem that will keep coming back?
 
  #5  
Old 11-08-03, 07:52 PM
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problems

they arn't self healing. You can be sure the problem is still there, it will hit you on Christmas eve midnight, with an outside temp of zero...never fails!
The fan you speak of .....which fan? combustion blower fan (exhaust), or the indoor fan motor? have you tried to raise the setpoint temp to lets say 80 to see what it does? Is this the same thermostat as last season (without any trouble)?
 
  #6  
Old 11-08-03, 08:02 PM
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also

as mentioned, there may be another air filter in the furnace return plenum...this is usually very close to the indoor fan motor...pop the cover and snoop around....make sure the return ducts are not blocked by furniture...ect. Get in the cellar and count the return registars and then locate them upstairs to make sure they are unrestricted. You may be going off on high limit. Do you have an AC coil in this system? Do you have access to inspect the face(inlet side)of this coil? If it's plugged, you'll have to clean it. Lots of people use cheap fiberglass filters and they let most all the dirt and dust pass through, and it collects on the wet coil face during the summer.
 
  #7  
Old 11-08-03, 09:58 PM
macv38
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Same issue!!!

I am having the exact same issue as Paladyr.

Here are more details:

1. The exaust blower comes on first.
2. Then the heating element comes on.
3. Then the three burners ignite
4. The heating element turns off.
5. The fan comes on (or doesn't come at all) and blows cool air.
6. Then everything shuts off 20 seconds later. Fan, blower, and burners.

When this first happened I changed the air filter on the furnace, b/c the old one was very dirty. This, however, did not seem to matter.

While I am watching the furnace turn on and off I touch the exaust pipe, and it is extremely hot. This is right after the burner come on. I don't know if it should be THAT hot. It seems as though the hot air is going there instead of through the fan to distribute through the house.

Thermostat has always worked. I have no reason to suspect it unless someone replying can give me a reason.

Any help FAST would be appreciated. It is very cold here, and will be for at least the next week.

Thanks.
 
  #8  
Old 11-09-03, 04:38 AM
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mac,

We need info on what brand of furance you got..


and how old it is.


Only thing I can think of off hand is maybe a flame sensor (If your has it) that may need to be clean.

But sounds like you have HSI (Hot surface ignitor), and it may needs to be replace since this is a sensor as well.. but DO NOT try to clean the HSI if you got one. Just needs to be replaced.

If you have metal exhaust pipe, yes, it should be hot.. Only one that will ever cool is the 90% with the PVC pipe.


Try this trick, turn the t-stat fan switch to "ON" and set the heat temp up, and see if the burner stays on the whole time.
 
  #9  
Old 11-09-03, 07:36 AM
macv38
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Jay,


Before I went to bed last night I set the thermostat to run the AC.
It blew hot air for 1 to 2 minutes then blew cool air. The outside temp here is 25 to 30 degrees at 9:14 am. I then let it run for about 5 minutes. I then turned off the AC, and set the thermostat to On instead of AUTO. This produced hot air finally for a steady amount of time! I ran it this way for about 20 minutes to warm up the house, and then set it back to auto. Now it seems to work sporatically. Sometimes it kicks on and off within seconds, and sometimes it runs for minutes blowing hot air.
The burners stay lit while the furnace is blowing warm air. This last time the furnace kicked on and off three times within a minute, and then finally kicked on for good and ran for a good 15 minutes blowing warm air.

Hardware info:

Name: Comfortmaker A/C and Heating - This is displayed on the outside panel that I remove to view the burners and exaust blower. Inside of this area where I removed this panel I found:

Inter-City Products, Lavergne, TN 37886
Model # GUI075A012IN
SERIAL # L923022080
MFG # GUI075AEIN

Name on the blower to push the air in the home:
The General 90
Inter-City Products
Total Furnace Control - Model 50A50-110

Information overload yet?

Thanks for the help.
 
  #10  
Old 11-09-03, 01:59 PM
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fan and limit

you MAY have a fan and limit switch, in which case it needs replacement. To test...run the fan motor in the on position and leave it there for a few days... if she runs OK, replace it. To replace... remove it and take it with you to match it up.
 
  #11  
Old 11-09-03, 06:48 PM
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I am with HVAC, and that what I was thinking it may be your fan control not working right for ya. So to get heat for now till you get the control changed, just turn the t-stat to "ON".
 
  #12  
Old 11-09-03, 07:19 PM
macv38
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Thanks for the replies.

I will mention this information to the technician I call out to my home. I figure with winter right around the corner that I might as well get it professionally fixed and inspected in case of any other defects.

Thanks again.
 
  #13  
Old 11-09-03, 07:22 PM
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Good Ideal Mac,

Get someone out to have your system checked, and clean... Please post back on what they have found..

:-)
 
  #14  
Old 11-10-03, 03:40 PM
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Well, tonight i left the fan on (instead of auto) and it still isn't heating the house.

How often are you supposed to have your heater "serviced?" Is it once a year? If so, then I might as well just do that and have them look at it.

I have a digital camera if anyone thinks that will help.
 
  #15  
Old 11-10-03, 04:21 PM
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Lightbulb no heat

Dont know what the furnaces are here 80 or 90 AFUE. But if fan control is ok, could be the Pilot ignition control modules. This will make your burner act up and then the fan wont have any heat to put in the home.


Yes it pays to have the furnace serviced each year ED
 
  #16  
Old 11-10-03, 06:34 PM
macv38
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Had the service techician out today. The flame sensor was dirty, and possibly defective so I had him replace the flame sensor with a new one, and he also cleaned out the entire furnace.

The heater is working perfectly for now, and the furnace is also spotless!

Thanks to everyone who responded with advice.
 
  #17  
Old 11-10-03, 10:05 PM
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Thumbs up

Good to see your back in bussiness, and warm!

Now I am sure you feel better now that your system is clean and been checked out for the winter month ahead of us.
 
  #18  
Old 12-01-08, 11:49 AM
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Similiar issue

With the t-stat in the heat mode and fan control in auto I can watch the heater start its cycle. The exhaust blower will start, ignitor will activate and the gas valve will open and unit will fire up but the main blower never comes on and after about 1 minute the unit will shut down on high temp limit (4 flashes). I have checked the pressure switch and the temp limit switch with my fluke meter and the contacts are starting in the correct state and proper voltage is present but the blower will not come on. I put the unit in the cool mode and the blower will come on as soon as it is called for. Any thoughts?
 
  #19  
Old 12-01-08, 08:25 PM
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Yes

your fan control is toast. Till you replace it, leave the fan in the on mode
 
  #20  
Old 02-16-10, 08:29 AM
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Same Problem - Different Result

We had the same problem as others in this forum. The heater comes on sporadically and shuts off before reaching the T-Stat setting. Some times it is only for a few seconds while other times it stays on for long periods of time (20-30 minutes)
We had a technician come out and "Look" at the furnace and his immediate diagnosis was to replace the Total Furnace Control. Then, our warranty company told us they would not pay for this replacement because we "failed to maintain" the unit. How do you maintain a solid state piece of electronic hardware?
After reading this forum I do not even think now that replacing this unit is the answer. I can provide as much detail as you need, as well as pictures.
Any help is greatly appreciated.
Rich
 
  #21  
Old 02-16-10, 04:01 PM
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Rich,

Do you have even a cheap volt-ohm meter to test with, if we tell you what to test?

Is the problem often enough to be pretty certian of catching it in the act, while testing?
 
  #22  
Old 11-27-11, 04:33 PM
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Problem Easily Fixed

Same problem as you all have had. Maybe a little different in that a
6 "blink" trouble code was displayed. The cure was to remove the heat sensing thermal couple and clean it with sand paper. After doing this the unit worked great. After thinking about it I think I would have used finer abrasive paper so that the sensor would be less likely to hold dirt. Procedure can be viewed on U-tube using this link. . . . http://************/c2ocxvv
Substitute the 12 asterisks with ************/ and the link should work. [************/
 

Last edited by awag123; 11-27-11 at 04:42 PM. Reason: not complete
 

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