Janitrol Furnace Quit

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  #1  
Old 01-04-01, 09:53 PM
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Cool

BRRRR..Who says Florida is the sunshine state? It's 25 degrees and my Janitrol furnace quit at 5 pm today. Glow ignitor works, but gas doesn't light. After an hour under the house, I managed to get it to fire by tightening elec. connections and then repowering thermostat. But after about 2 minutes the flame cuts off and won't restart until I turn off thermostat, wiggle connections or wait, and then try again about 15 minutes later. Can't stay under the house all night. My thoughts: 1) Janitrol site says the furnace (GMP100-4) should have a 13709-05S 3" 290F limit switch. The one I found in place is a Texas Instruments B13700-03. Could that be the problem? 2) I read on this site about ground problems regarding circuit board connections. A tech replaced the circuit board last year and it has worked fine until today. Could it have been a bad ground all along? 3) Had an LP gas delivery yesterday after running the tank low (to 5%). Does bottom gas foul the valve? Any thoughts on this kind of problem? Sure would appreciate some sound advice from an experienced repair guru. ...Bob in Tallahassee
 
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  #2  
Old 01-05-01, 03:24 PM
fjrachel
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To answer your questions: 1) that is a valid Janitrol # on your limit and that is not the problem. 2)I doubt that the board went bad do to a grounding problem, it may have just went bad if that's the case. 3) did your lose heat due to the low LP tank? If so, bleed the line. You could also have a frozen 2nd stage regulator. Is it wet in the crawl? I'd go with a gas problem. Have the LP company check it out.
 
  #3  
Old 01-05-01, 07:55 PM
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Thanks for the advice

Thanks, fjrachel, for helping sort out the possibilities. I'll call the lp company. The crawl space is dry and not sub-freezing. Also, the hot water heater runs fine (it has a standing pilot). The red light on the furnace circuit board is supposed to blink out trouble codes if something is wrong, but it stays on constantly when the thermostat calls for heat. I did shut off the gas when the tank ran low to curtail lp tracer odor, but have run three two-minute burns on the furnace since then. It cuts off after about 2 minutes and won't restart (flue vent fan runs, glow ignitor glows, but no gas flame.) I priced a circuit board but supplier refused to sell to me (I'm not a licensed contractor). Service call will cost more than the board. So I'll try lp company before service call if I can reach anyone on Saturday. Thanks again for the sound advice. -- Bob Macmaster
 
  #4  
Old 01-06-01, 05:00 AM
fjrachel
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Try this. Check for moisture in your forced draft proving switch. It's got the rubber 1/4" tube going between it and the forced draft housing, remove tube from switch & housing and drain. Also remove your flame sensor and clean it lightly with fine sand paper. It is located on the opposite side of the Hot surface ignitor in burner section.
 
  #5  
Old 01-07-01, 07:42 AM
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Closer to solving problem?

Polished (with 150-grit sandpaper) the flame sensor and removed/checked the vaccuum switch per your suggestion but there was no improvement in the system so I called the LP company. The LP company service technician returned my call in 10 minutes (great service) and stayed on the phone while I tried firing up the unit. I described the system operation as he listened. I turned on the power switch to the unit (thermostat was preset for at 88 degrees). The combustion blower started, and after about 20 seconds the ignitor begasn to glow but just as it reached bright orange (after about 7-8 seconds) there was a click and the ignitor began to cool. No flame. The technician said "that's wrong, the ignitor should stay on for much longer." He said it's not the ignitor but the circuit board that would cause a fault like that (although I asked him if the ignitor had a crack, could it break the circuit when it heated - he said no - ignitors either work or don't work.) So I plan to buy a circuit board and plug it in (replacing wires to like positions) when the store opens Monday. They won't sell to me but I found a tech who can't come for several days but will let me buy on his license. Thought I'd replace the flame sensor and ignitor at the same time since they are $5 items. Does this sound right? Bob in Tallahassee.

[Edited by rmac on 01-07-01 at 11:15]
 
  #6  
Old 01-07-01, 09:07 AM
fjrachel
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I've run into this type of problem before with the timing and the HSI(hot surface ignitor). If you have your installation paperwork.......It has a timing sequence for the heat. Time it... Yes change the HSI, it may be taking too long to glow and loses it's heat too quickly. If to much resistance, for whatever reason, builds up in the ignitor it will take longer to reach glow point and when the gas valve opens, it's already losing it's glow, due to the power timing to the HSI.
 
  #7  
Old 01-10-01, 07:25 PM
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Still freezing ... puzzle continues

Replaced HSI module (circuit board), HSI ignitor and flame sensor. Similar behavior as before. On first powerup, combustion blower comes on, 25 seconds later ignitor begins to glow, 9 seconds later a click and ignotor fades. Still won't light but new circuit board flashes 3-pulse sequence. That, according to decoder inside secondary door, means vaccuum switch is not sending the right signal. Is this a make switch? If so, I can I bypass it temporarily by connecting the two orange leads to each other to prove that's the problem. You suggested removing and checking for moisture, which I did and found none. But the internal terminals could be corroded. I still would like to replace the limit switch but can't get one. Parts house ordered one Monday but no joy ... they don't know when it may arrive. Goodman site says my furnace needs a 290 degree switch, but label in door says 245. Any idea which is right? And how about the transformer. Could it fail under load. THese are just my"ideas" ...can you help me narrow the search? THanks for your ongoing help. ..rmac (Bob in Tallahassee)
 
  #8  
Old 01-11-01, 01:45 PM
fjrachel
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Induced draft psi sensing switch operation: Switch must be open for induced draft motore to start(if closed on call for heat motor will not come on), draft motor closes switch which starts ignition sequence. If the psi sw. opens during operation, the unit will shut down, the draft motor will keep running and try a restart. To check: call for heat, after induced motor start, jump out switch. If it keeps burning you found the problem. Did you check the switch and hose for moisture?
 
  #9  
Old 01-11-01, 06:31 PM
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Thanks, fjrachel, for sticking with me on this long task. Glad you told me about the requirement for the psi switch to be open on startup or I might have made a wrong diagnosis. Yes, I checked the hose and removed and inverted the switch to check for moisture. Found none. Replaced the hose with a new, tighter-fitting one, but still the same problem. From the sound of what you described about the operation of the system, this could be the problem. I opened the vent port and removed the combustion blower the be sure there was no obstruction. The only possible deterioration was a little rust on the little orifice fitting that attaches the 1/4-inch hose to the combustion blower. However, it was not blocked. I also climbed atop the chimney and looked down to verify it was clear and it was. Will now jumper the switch and let you know tomorrow if it works. May also try a resistance check (ohmmeter) on the switch while drawing air on the switch hose. Assume it should complete the circuit if the contacts are good. Thanks again for all your help. This forum is terrific. -rmac
 
  #10  
Old 01-11-01, 07:07 PM
fjrachel
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Clean the rust out of the induced blower housing port. The slightest bit of restriction will do it. A piece of 18ga. t'stat wire is about the right size. Check that induced draft blower wheel too. You've gone this far. Good luck...
 
  #11  
Old 01-13-01, 08:10 AM
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Success! We've got heat.

To fjrachel: My Janitrol GMP100-4 is back in action and runs even better than before it quit. It's been a long week with temps below freezing every night, but the fireplace kept the house bearable. The limit switch arrived at the supply house from Goodman Friday afternoon, and I picked up a new pressure sensing switch at the same time. (the old one tested poorly on an ohmmeter) Put 'em in and also ran some braided wire through the vaccuum port on the blower to clean out internal rust. Fired it up at 8 pm last night and it's running smoother, quieter and with longer, less-choppy cycles than before it failed. I suspect the new limit switch (matches Goodman's specs) and the new circuit board (allows fan to run longer after gas shuts off) help smooth the cycling. Found and repaired many loose connections during the diagnosis. Thanks, fjrachel, many times over for your advice and support during this adventure. You stuck by me when the local hvac company let me down. Hope your site owners realize what a great job you do for homeowners who otherwise are at the mercy of less skilled HVAC doctors. Wish you worked hvac in my area. -rmac
 
  #12  
Old 01-13-01, 11:32 AM
fjrachel
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Your very welcome...After this one though, you should know your machine pretty well and I hope you saved all the old parts. They will come in handy. Good Luck.......
 
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