furnace blows but no heat

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  #1  
Old 02-21-04, 09:54 AM
oberfam
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furnace blows but no heat

have a lennox wisper heat not sure of age. pilot light is lit, blower works. we had someone come and look at it. it worked 70% of the time. after they left didnt work at all they came and replaced the gas valve worked for a day. if we shut it off and turn it back on it well work for a while but than have to shut it off and start all over again. any advise would be greatly appreciated
 
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Old 02-22-04, 07:18 AM
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oberfam's Whisper Heat No heat.

oberfam,

Somereson your thread was "closed" so figured I'd reply here for you.

Does the damper door stay open the whole time when it calls for heat?

Flame sensor been cleaned?
 
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Old 02-22-04, 08:07 AM
oberfam
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Re: oberfam's Whisper Heat No heat.

Originally posted by Jay11J
oberfam,

Somereson your thread was "closed" so figured I'd reply here for you.

Does the damper door stay open the whole time when it calls for heat?

Flame sensor been cleaned?
Sorry dont know how to open my thread. The damper door does stay open and the flame sensor has been cleaned.
 
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Old 02-22-04, 08:27 AM
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Hi: Gents

In responce to the original thread being closed, it was done either unintentionally or accidentially by the member. No harm and no foul....

The two threads are now combined (have been merged) and the thread is now reopened for additional postings...

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Old 02-22-04, 10:33 AM
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i assume this is a standing pilot unit? if they changed the valve already, may be losing voltage on control wire before the valve. does this unit have a circuit board?
 
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Old 02-22-04, 01:09 PM
oberfam
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Originally posted by hvac4u
i assume this is a standing pilot unit? if they changed the valve already, may be losing voltage on control wire before the valve. does this unit have a circuit board?
YES THE FURNACE DOES HAVE A CIRCUIT BOARD.
 
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Old 02-23-04, 04:38 AM
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It sounds like you are going out on a safety. Have you changed the filter lately? If so what kind are you using? Also when was this furnace cleaned by a HVAC tech last?
 
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Old 02-23-04, 02:31 PM
oberfam
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Originally posted by mattison
It sounds like you are going out on a safety. Have you changed the filter lately? If so what kind are you using? Also when was this furnace cleaned by a HVAC tech last?

We just use the cheap filters, change them once a month. They cleaned the furnace the same day they broke it. Before the changed the valve.
 
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Old 02-23-04, 09:56 PM
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G-20 is the model for the Lennox Whisper Heat.The 3rd & 4th numbers of the serial # is the year manufactured.Have you cleaned the flame sensor?That's the little metal rod that sticks into the pilot flame.It has a wire running from it to the ignition module terminal labeled "Flame Sense","Sense",or"FS".To clean the flame sensor:Shut off gas and power.Remove pilot tube from gas valve by loosening the brass fitting with a 7/16 open end wrench.Remove the 2 screws that hold the pilot assembly.There should be 2 wires going to the pilot assembly,one is the spark wire,the other is the flame sense wire.Disconnect these wires at the ignition module,or at the pilot assembly if possible(you should be able to tell).Carefully remove assembly,(thats the pilot and pilot tube).Clean the little metal rod that sits in front of the pilot hood that aims the flame to it.Use 0000 extra fine grade steel wool,or Scotch-Brite scour pad.Don't use sanpaper.O.K...now reassemble in reverse order,being certain the spark and flame sense wires are put on the correct terminals.Turn on gas and power and check operation.I should have brought this other point up before....What does the pilot flame look like?Is it yellow?Like a candle flame?If so,the pilot is probably dirty and needs cleaning,alas,my fingers are too tired to give step by step directions.After all this...frankly....from personal experience,I think your ignition module is working intermittently.If a safety was opening,I doubt the furnace would light right back up after you turned it off,then right back on again.But without the aid of reading microamps from the flame sensor,it's still a"hipshot" troubleshoot.But I got a feelin' that's what it is.The Module.Probably a Robert Shaw.If you decide to replace it,replace it with AN EXACT MATCH OR ONE CROSS-REFERENCED BY AN HVAC SUPPLIER.and if you don't feel completley confident doing the job yourself,then DON'T!Have it it done by an experienced service person.
 
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