Blowing unheated air, no ignitor clicking sound

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Old 01-30-13, 09:26 PM
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Blowing unheated air, no ignitor clicking sound

The 20 year old Day and Night Furnace all of a sudden stopped blowing warm air. The unit has been repaired by a technician couple of summers ago and had the ignition module replaced (a refurbished Honeywell S8600h 1006).

After closer inspection, I confirmed 25.4v at the transformer, but 0v at the ignition module while the blower is running. Could it be a faulty Limit Switch Control? Is there any way to test it?
 
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Old 01-31-13, 11:58 AM
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Most likely you have a switch open that is preventing the 24 VAC from powering the ignition module.


Take the cover off the burner compartment of the furnace.

Get the model number of the furnace off the rating plate in the burner compartment and post it here.

Describe in order the sequence of events which occurs when you turn up the thermostat in as much detail as possible.
 
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Old 01-31-13, 02:15 PM
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Ok, had more time to diagnose today. I did get 25.+v to the ignition module (for the very first few miutes of turning the furnace on). There is .9v between mv/pv and pv. Zero V between mv and mv/pv.

Sequence is:
1. turn on the furnace
2. get 25.+V between 24V(grnd) and 24v
3. no V between MV and MV/PV
4. minor V (like .9 v)between MV/PV and PV
5. blower runs continually with cool air

Carrier corp. model#: 349jaz036060

thanks
 
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Old 02-01-13, 01:43 PM
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Sorry, but your description is too vague and incomplete for me to be able to help you.
 
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Old 02-05-13, 02:30 PM
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Bit the bullet and bought a new Ignition control module. This time I replaced it with ICM290A, which was cheaper ($89).

Now I get 25v across MV/PV Terminal and PV, plus a nice pilot light. But 0v across MV/PV and MV. Thus no heat. What gives?
 
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Old 02-05-13, 08:58 PM
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Problem solved!

My heater has the most primitive setup consisting of just: blower, limit control, magnetic switch, 24v transformer, ignition module, pilot burner/ignitor, combination pilot/burner auto gas valve, two rollout limit switches, and a burner.

I have read on this and other forums that if maybe the pilot flame sensor needed cleaning. This particular unit did not have a flame sensor. I scratched my head and looked all over. There were no extra wires or a sensor at all besides the pilot ignition. I thought "what the hell" and removed the pilot assembly and took a sand paper to the rod where the spark comes out of. Lo and behold, that pilot ignitor WAS the flame sensor (it had a dual purpose)!

I put everything back together, the pilot assembly nice and shiny, a new ignition module ICM290A (with the fancy LED lights), wired the 24v to the TH-W terminal. At the thermostat, I flipped on the heater switch, pilot ignitor sparked, then the pilot flame came on, (oddly the spark kept going even after the pilot flame was going), few seconds later the burner kicked in, then the blower, and rejoice! We have warm air coming out the vents!

Thanks everyone for your help.
 
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Old 02-06-13, 09:04 AM
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Well, I thought the problem was solved... This morning the Furnace failed again.

No pilot ignition. What gives?
 
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Old 02-06-13, 09:29 AM
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It appears that most of this thread is just you talking to yourself. I would suggest that you provide the information that SeattlePioneer requested.
 
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Old 02-06-13, 12:39 PM
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Ok, sorry.

Lets try this again.

Model number:
349jaz036060

Product number:
349jaz036060aaaf

Carrier corporation

Manf. Number:
6072529037

Sequence of events:

Call for heat,
Ignitor sparks,
pilot flame comes on (0.7v across MV/PV and MV),
Burner does not ignite,
blower comes on flowing plain air.
 

Last edited by oracle911; 02-06-13 at 02:51 PM.
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Old 02-06-13, 01:40 PM
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You should not have used sand paper! You can try to clean it with seel wool, but you likely left sand on the spark rod and it has now turned to glass on the rod which acts as a insulator to the flame. If steel wool does not do the trick you may need a new pilot/spark assy. Having said all that, it may be that your ICM control is faulty. I have had MANY ICM controls that have not worked well as oem replacements.
 
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Old 02-06-13, 02:50 PM
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Just replaced it with a new ICM290A which is a S8610U direct replacement, and yes I did remember to plug the 24V wire into TH-W plug instead.

I did later realize sandpaper was a no-no. I just polished it with steel wool and cleaned off all the loose debris. The pilot /spark assy visually looks flawless. No cracks, no holes or rust. Just normal discoloration from the flame.
 
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Old 02-06-13, 03:05 PM
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I understand it is a direct replacement, but ICM spark products have failed very often on me. I no longer use ICM spark ignition products and always use Honeywell S8610U3009 for replacements
 
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Old 02-07-13, 09:51 AM
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I guess I should have sprung the extra $10 and got the Honeywell instead. Where do you get yours and how much?
 
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Old 02-07-13, 03:08 PM
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I get mine through our supply houses. You can get them online at a lot of places or if you have a Graingers close by they should have them.
 
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