Ducane Natural Gas Unit won't light up

Reply

  #1  
Old 12-04-14, 07:24 PM
Member
Thread Starter
Join Date: Aug 2012
Posts: 9
Received 0 Votes on 0 Posts
Ducane Natural Gas Unit won't light up

My Ducane gas furnace is refusing to light!

My furnace was working fine till last week. We went out of town for few days and I lowered the temp to save some money. After coming back, I raised the temp settings but it wont start.

If I put my fan to manual ON setting, it blows cold air but no sign of pilot ignition. If I change my fan settings to AUTO, I hear a click followed by humming coming out of exhaust draft inducer, followed by another click and nothing else. Same cycle start after few minutes but nothing else. I checked the pilot, it's not igniting at all.

I have removed the tubes (2) going into the pressure switch and do hear clicks if I blow or suck some air through the tubes but that didn't make any difference in furnace behavior.

Here is what my furnace look like after removing the panels. Any idea what might be wrong ?


 
Sponsored Links
  #2  
Old 12-04-14, 08:11 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Received 0 Votes on 0 Posts
Welcome to the forum!! Are you saying the draft inducer is not running but only humming? To better assist, please post model number of furnace. The model number should be found on a label on the right inside wall near the pressure switch,
 
  #3  
Old 12-08-14, 12:38 PM
Member
Thread Starter
Join Date: Aug 2012
Posts: 9
Received 0 Votes on 0 Posts
Thanks,
Yes, that is correct. The draft inducer is not running but only humming when thermostat sends a heat signal. The model number is CMPA075U3.
 
  #4  
Old 12-08-14, 12:42 PM
Member
Thread Starter
Join Date: Aug 2012
Posts: 9
Received 0 Votes on 0 Posts
And when I turn the thermostat to cooling mode and lower the temperature below the room temperature, it works. Cooling is working but the heating is not.
 
  #5  
Old 12-08-14, 12:44 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Received 0 Votes on 0 Posts
It sounds like you have probably either have a bad control board or a bad inducer motor. During a call for heat you will need to see if you are getting 120V out of the terminals (probably DI and Neutral terminals) on the control board that supply voltage to the inducer motor. If not, the board is bad. If the board is sending 120V to the inducer but the inducer does not run, then it is bad. Some of the older inducer motors had oil ports that allow you to oil the motor on a routine basis. Newer ones are sealed. I suggest you remove the inducer and spin the blower wheel by hand to check the bearings and see if it will spin. You can check and see if there are any oil ports and put some oil in to see if you can get it going. Sometimes a person gets lucky. Also, check the terminals on the board where the inducer motor leads connect for corrosion.

Here is a link to the installation manual for your furnace in case you don't have it:

http://c.searspartsdirect.com/mmh/li...L/L0212120.pdf
 

Last edited by firedawgsatx; 12-08-14 at 02:07 PM. Reason: Added link
  #6  
Old 12-08-14, 02:26 PM
Member
Thread Starter
Join Date: Aug 2012
Posts: 9
Received 0 Votes on 0 Posts
Thanks, I checked the voltage and I am getting 120V going to the inducer motor. What should be the sequence of operation when the unit gets a heat command ? Should I see inducer motor running before activating pressure switch and ignition ?
There is a big capacitor outside of the inducer motor ? Do you think there might be something wrong with the capacitor ? I touched the motor and I can feel some heat, so it can't be dead and I think it is a sealed motor.
 
  #7  
Old 12-08-14, 02:41 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Received 0 Votes on 0 Posts
Looks like you have a bad inducer motor. The sequence of operation is: the inducer should start up right away, the pressure switch closes, smart gas valve energizes pilot gas valve, pilot lights, pilot is proven, main gas valve opens and pilot lights main burners, blower comes on and furnace continues to operate until it reaches the temperature set at the thermostat. That capacitor you see is for the blower motor and not for the inducer. If the motor just hums and gets hot it points to a bad motor. If you check the wiring diagram on page 21 of the installation manual I linked in my previous post it will show the capacitor going to the blower motor. See attached diagram.

so it can't be dead
If you think it can't be dead, go ahead and remove the inducer motor leads from the control board and put them into an extension cord. Then plug the extension cord into a wall outlet. If the motor is good it will start right up.
 
Attached Images   

Last edited by firedawgsatx; 12-08-14 at 04:58 PM.
  #8  
Old 12-12-14, 11:26 AM
Member
Thread Starter
Join Date: Aug 2012
Posts: 9
Received 0 Votes on 0 Posts
Thanks... Can you please verify if I am identifying the right component as inducer motor because the capacitor i was referring to is actually mounted on top of the motor I thought is inducer motor. I have attached a pic and if you can validate, that would be great help. If this is an inducer motor, which one is blower ?Name:  HVAC.jpg
Views: 4327
Size:  42.7 KB
 
  #9  
Old 12-12-14, 11:48 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Received 0 Votes on 0 Posts
Yes, the item in your photo is the inducer motor. The wiring diagram does not show a capacitor for the inducer motor. The circulation blower will be located in another compartment below (if upflow) where the inducer is located. Since your inducer motor has a capacitor that could hopefully be your problem as that is a much cheaper part than the inducer motor. Is the top of the capacitor bulging? It appears to be from the photo but difficult to tell.
 
  #10  
Old 12-12-14, 12:07 PM
Member
Thread Starter
Join Date: Aug 2012
Posts: 9
Received 0 Votes on 0 Posts
Excellent !!!! I am little optimistic now. So if the capacitor is bad, inducer motor won't start right ? I can try replacing the capacitor and hope it will start.

There is no bulge on the capacitor, what you might be referring to is the protective rubber casing to cover the wire connections on the capacitor.

Is there a way to check if the capacitor has gone bad. Should i short circuit the capacitor connections ?
 
  #11  
Old 12-12-14, 12:23 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Received 0 Votes on 0 Posts
Yes, if the capacitor is totally bad the inducer motor won't start up. To check the capacitor to see if it is within specs as listed on the label you need a meter with the capacitance testing feature. Most DIYers replace the capacitor because it is relatively cheap and easy to obtain. Just match the specs listed on the label and you should be good to go. If you have a local Grainger's they will have it on the shelf.
 
  #12  
Old 12-12-14, 12:23 PM
Member
Thread Starter
Join Date: Aug 2012
Posts: 9
Received 0 Votes on 0 Posts
The capacitor on the motor is York SFA374A14
 
  #13  
Old 12-12-14, 12:27 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Received 0 Votes on 0 Posts
You can use any capacitor with the same microfarad rating. That capacitor has a rating of 4uf/370V.
 
  #14  
Old 12-12-14, 12:32 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 13,936
Received 1 Vote on 1 Post
If your meter has the capability to measure microfarads, you can test the cap. Unplug the wires from the cap, short the terminals with a well insulated screwdriver just in case the cap doesn't bleed down on its own, connect the meter & read the microfarads vs the label on the cap. You can probably replace the cap for under $10.
 
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
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: