Comfortmaker Furnace won't light


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Old 12-29-13, 04:04 PM
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Exclamation Comfortmaker Furnace won't light

All,

Thanks in advance for any help you may be able to provide!

Model details:
Comfortmaker RPJ II
Model No: GNE100F14A1

Personal Experience level:
I worked HVAC for five years in California, installing tons of systems as part of a crew. I never did repair work however, so this is still a learning process even though I am familiar with the system. I can work a multimeter and I'm pretty mechanically inclined.

Problem Sequence of events:
1. I noticed a squeal coming from the heater for a week or so. I figured "darn, blower is going out soon." and basically just figured I'd let it ride until it died. Everybody makes bad decisions from time to time...

2. Heater stopped working. (I live in Illinois now, so it was noticeable!)

3. I went down and heard the draft inducer buzzing but not moving air. I grabbed the black wheel on it and gave it a spin. It jumped to life but sounded squealy, and then slowly gave up the ghost and went back down to a stop- continuing to buzz, so I cut power to the heater to keep it from burning up the motor.

4. Well, immediately I realized I was wrong about the blower! I removed the tube from the pressure switch and condensate came flowing out. Then I removed the draft inducer (messing up the fiberglass gasket a little in the process, but it should be fine)

5. The fan blades were pretty dusty, and the shaft was tough to turn even by hand! I blew it all out clean, and lubed up the motor shafts with WD-40 (it's all I had on hand! I knew it wasn't ideal and would need to be replaced with a better machine oil- but I needed to get the heat back on so it worked as a band-aid) After cleaned and lubed, the shaft spun like a top by hand!

6. I re-installed the draft inducer, and BINGO! The draft inducer runs like a dream, the pressure switch kicks, and the furnace lights like clockwork. The heater kicked on like a champ. Problem solved! …Or so I thought…

Fast Forward Three Weeks….

7. Went to visit relatives for the holidays and our dog sitter (my father-in-law) said the heater died. (great…) Well we couldn't come back for a few days so I described the procedure to him to lube the motor up. I was thinking the WD-40 had run it's course and left the motor struggling again, so I told him to pick up some actual machine oil and lube it as I had.

8. He "lubed" it with graphite paste as it turns out… and when that didn't work he attempted to jumper the wires of the pressure switch. The heater still didn't work and the motor wasn't performing.

9. I get home last night- house is predictably freezing. I check the draft inducer- and it's bad man. It is pretty difficult to turn by hand. I remove it- clean it, and lube it with machine oil. It spins like a dream again. I re-install it thinking it will live to fight another day…

10. The draft inducer runs like brand new again, but it's not tripping the pressure switch now! I check the pressure switch by sucking on the tube- it seems to be working there- and no condensate in tube was found this time (understandably though, as the heater hadn't been heating) I hooked a multimeter up to it and sucked on the tube- the switch is working. I checked the "nipple" the tube connects to on the draft inducer- it is clean and free of obstructions. I checked the tube- no cracks or holes. I checked the exhaust vent for possible obstructions, and even removed the vent temporarily to test if a blockage was interfering with the vacuum- it doesn't appear to be. I also checked the condensate drain tube- looks clear.

11. Now the curious part- I tried two things: A. I put the tube in my mouth and simulated vacuum pressure when the draft inducer kicks on, and let off when the inducer was shut off- the pressure switch clicked like it should, but the furnace never lit. B. I jumpered the pressure switches wires to simulate a closed switch, and even though the inducer and blower are running just fine, the furnace still never lit.

12. This made me question the leads running into the pressure switch. I stuck a multimeter to them and got no voltage, ever. That doesn't seems good to me…


Synopsis:
I already have a new draft inducer in the mail (arrives tomorrow) as that was for sure my initial problem, however now that my father-in-law monkeyed around it seems I have another issue at hand as well? What steps should I take to narrow down my issue and get my furnace working again? My house is freezing!
 
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Old 12-29-13, 05:12 PM
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Welcome to the forums.

Your first step is to get the new draft inducer blower installed.

Some control boards will only light if the pressure switch is closed in the proper sequence.

The following link is the manual for your unit. You could check for voltages using that.


Sears parts direct/ICP download/lis_pdf/INSTL/L0502528.pdf
 
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Old 12-29-13, 06:52 PM
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Thanks for the quick reply!

The manual seems to stop on page 16 right when it begins to talk about pressure switches... Is half the manual missing?

Also- from looking at it, the signal path seems to run like this:
PCB-> Main Blower-> Pressure Switch-> Igniter

Which to me says that there should be voltage running thought the leads connected to the pressure switch at some point, but there never is. Oddly enough, the main blower runs just fine. Since the power runs directly from the blower to the pressure switch- perhaps there is a break in the wire between the two? I haven't been able to check that yet since to get the main blower out I have to disconnect all the thermostat wires because they aren't long enough.

Any thoughts? The pressure switch should be getting voltage right?
 
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Old 12-30-13, 12:51 PM
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UPDATE: (Still need help!)

New inducer arrived, and installed.

It runs great, and activates the pressure switch like it should (as evidenced by the little click noise AND by a multimeter testing continuity of the pressure switch leads as it activates. i.e.: my new inducer is doing what it is supposed to- and the pressure switch is functional.)

HOWEVER- there is still never any voltage at the pressure switch incoming lead.

I have tested continuity of the wire from the pressure switch, through some switch on the main blower, through another switch on the opposite side of the main blower, back to the main PCB, and found no breaks in the wire or erroneous open switches that would be stopping the signal path…

To recap: Main blower works, inducer works, system kicks on when called for heat, pressure switch works fine mechanically- but is receiving no voltage.

Could it be an open/faulty high limit switch somewhere? (I actually don't even know which switches those are… I just know they are in the mix somewhere)

I am hoping this doesn't point to a bad main circuit board!
 
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Old 12-30-13, 01:37 PM
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UPDATE to the UPDATE:

Long story short: FIXED!!! (Hopefully- please see remaining question at end)

Short story long: So I put everything back together and I realized that I hadn't actually seen the inducer kick on when the thermostat called for heat- I just always had the thermostat set to heat and I would cycle the unit power via a switch on it's side when I needed it on or off- THUS, every time I turned on the unit via the switch, the inducer just began to run.

I wanted to know if it would stop running if the thermostat stopped calling for heat. I went upstairs, and turned the T-stat from "heat" to "off". Next I went downstairs and turned power on to the unit. To my dismay- the inducer began running anyway (is that normal!?)

However- I noticed now that the main blower WASN'T running… which it had been doing all through my troubleshooting! I began to think "GREAT! Did I manage to screw up something ELSE!?"

I went back upstairs and turned the T-stat back from "off" to "heat", and heard it click on. Then I walked back downstairs to the unit to discover… A PILOT LIGHT!

FLAME!!!!!!! I watched in wonder as the little pilot gave way to a burner full of glorious flames- and shortly thereafter the main blower came purring online- heat flows once again in the house!!!

I am only left with the one burning (pun intended) question: Should my draft inducer be running when the system isn't calling for heat?
 
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Old 12-30-13, 02:12 PM
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After the unit appears to be operating normally...... does the inducer still continue to run after the burner shuts off ?
 
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Old 12-30-13, 08:03 PM
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Yes, it does…

What does that mean?
 
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Old 12-30-13, 08:21 PM
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It sounds like the relay on the control board that operates that blower is stuck closed.

Sometimes you can tap on the relays with the back of a screwdriver to unstick them.
 
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Old 01-12-14, 11:46 AM
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So I tapped on the relay and you were correct- it shut off the draft inducer. However- it seems to be sticking every time- and if I tap on it while it's off, it will turn on and stay on until I tap it again. Is this something I can replace? I have pictures of what my circuit board looks like as well as a close up of what I'm tapping on but I'm not sure how to upload them here from my phone yet
 
 

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