Furnace induced draft blower runs continuously

Reply

  #1  
Old 10-21-12, 05:43 AM
A
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
Furnace induced draft blower runs continuously

I'll make this quick...my furnace will properly complete 1 cycle of heating only after being power-cycled with the thermostat calling for heat. When the room temp drops below set-point and the thermostat calls for heat, the burners fail to kick on and I get an associated LED fault code of 2 flashes, meaning "Pressure switch circuit is closed -- ID blower is not operating" according to the manual.

However, the ID blower actually is running. I replaced the draft blower pressure switch, but the same thing keeps happening. The blower runs continuously. The pressure switch hose is fine, as are the flue, air inlet, & drain system. When I unplug the pressure switch, the fault code changes to 3 flashes.

Any ideas? Any help is greatly appreciated...
 
Sponsored Links
  #2  
Old 10-21-12, 06:51 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,245
Received 2 Votes on 2 Posts
If the draft inducer blower does not shut off after a call for heat then that is a problem that the control is recognizing by seeing a closed circuit on the pressure switch when it should be open without a call for heat. This is likely caused by the control board inducer relay being stuck closed. Can you please verify if the inducer shuts off without a call for heat?
 
  #3  
Old 10-21-12, 10:09 AM
A
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
Yes, the inducer runs when there is no call for heat.

I must reiterate that the problem is that the furnace fails to run a 2nd cycle. I don't understand why it will run fine initially but fails to do so without being power-cycled. Also, the fact that the error code is telling me the DI pressure switch is closed when in fact the blower is running continuously is troublesome.
 
  #4  
Old 10-21-12, 10:18 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,245
Received 2 Votes on 2 Posts
you dont understand how the system works...

It will run the 1st cycle because the power was off and the inducer was not running which will mean that the pressure switch circuit was OPEN. It will not run the second cycle due to the inducer not shutting off and the pressure switch not reopening. The pressure switch circuit closes when the inducer runs.

You need a new control board.
 
  #5  
Old 10-21-12, 12:55 PM
A
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
You are correct, I don't know exactly how the system works...hence the forum. Just trying to avoid technician costs if its something simple. Thanks for your help, makes sense, hopefully it pans out.
 
  #6  
Old 10-25-12, 06:50 PM
A
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
hvactechfw, you nailed it. Running like a charm and the wife is happy. Thanks a lot.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: