The brief but imo best answer to your quandary as well as saving you from throwing parts at things in the future. Buy a meter and learn to use it. Greenhorn techs or those who refuse to advance their knowledge throw parts at problems til it;s fixed or the customer go's broke. The best tech in the world can not diagnose without a meter,much less long distance over the net. Odds are the draft motor switch is bad,briefly wire around it to find out. If that doesn't make the motor run,go buy that meter and come back,we'll tell you how to test motor in 5 minutes. $10 will get you one that works for what you need,$50 get's you one fit for a pro,$400 buy's one that will not be damaged falling off a ladder,last for decades and has additional functions only usful after advanced formal education.

This furnace has a 10 year parts warranty. Have you discussed the problems with the original installer? Who has been swapping the parts so far?

Don't assume it bads parts, a poor installation can also cause these types of problems.

Good point mike but I'll telluwhat (sp intentional). If I find out this is another case of consumers gathering info to assist pros that can't solve a problem I may just fall on my sword.

guys, thanks for your input. klem1, i have a couple of meters already and build simple electronic circuits in my spare time (electric guitar fuzz and compressor pedals). the inducer runs without noise on start-up. never fails. i get good heat cycles 80%+ of the time, but cycles miss (ignitor nice and bright, then initial flame, substantial enough (full) so that the flame sensor senses the heat, then the flame goes out and the blower continues to run). mike_home, i replaced both the ignitor and flame sensor with new TRANE parts i purchased from my installer towards the end of the last heating season. problem seemed to go away, but then again, since it was late spring, most of the heating load was carried by the heat pump. i know my installer pretty well, and even though i am a total novice when it comes to HVAC, his work appears orderly and thorough. i have also checked for condensate in the lines, and even though they are moist, they appear to be draining properly so as not to cause a clog. klem1, no worries on that! i just like fixing things myself. my installer actually supports my "interest" somewhat, but i would always call him on something big. he is very busy all the time, so something like this shouldn't be too much of a challenge. it's just that i'm trying to avoid the service call. i know...sounds bad...but with info that can be gleaned on the internet, why shouldn't i at least try to solve my problem.

correction: problem just occurred again. call for heat, inducer motor comes on and ramps up rpm, ignitor lights bright, i hear the click for the gas valve to send gas, valve opens and sends small amount of gas, first burner fires and then the gas valve closes, no fire, no heat. there isn't enough gas to get all the burners to fire, so the flame sensor located at the furthest burner away from the ignitor is not picking up the heat to continue the cycle, and then the furnace continues to run. it's blowing cold air as i type this. this is looking more like a gas valve problem or a board issue. i will go ahead and clean the flame sensor, but honestly there doesn't seem to be enough gas being delivered to the chamber to fire all the burners.

Don't take offense from my little rant,i just have to vent from time to time. (: . Considering your hobby,you have sufficent understanding of simple schematics, continuity,voltage drop and testing for presence of voltage to check this out. Look once more at light and what it says on door they mean. You might be on to something with gas valve but keep in mind that ever possible problem defaults to that valve. Shut the gas off and nothing bad can happen is the reasoning. Look scamatic over carfully and make certain everything is in place. Not to beat on your service guy but all of us ( well except the few that are perfect) have failed to reinstall a shield causing roll out safty to activate. Make sure everything near burners is in proper position so theres no rollout shut down. Induced drafts can be touchy plus some manufactures designed one that is two step,validates once before allowing pilot to light then again to make sure flow is ample before lighting burners. Not only does fan have to run, CFMs must be up to specs. I've been away for a while but most used a "sail switch"which can be manually overroad by holding sail up with finger tip. Do not perminatly wire around any switch any longer than nessary for tests. Look carfully to make certain exhust/flue isn't obstructed by mud dauber or bird nest. Furnace is largest consumer of gas in the house. Water heater and range might recieve enough gas although meter or supply line is partly plugged. How old is house? Turn on all other gas appliances to see if that farthur restricts flow at burners. Ok,if you are 100% certain you follow what I'm saying and are comfortable with doing it. While valve is trying to open,establish polarity of terminals. Use a 2 wire jumper from transformer to valve as soon as flame begains during normal start up. If burners don't operate,check for spider webs and such in burner. If all burners light and burn full,that 90% says valve is not where problem lies. You will need to back track from valve to and through safty switches to find which then why is breaking circuit. That should keep you busy for a spell. If your eyebrows are singed when you return we will know things didn't go as planned. ):

thanks, klem. 'bout died when i read your last sentence above. LOL. so, i inspected both the ignitor and flame sensor. both are pristine new, but i went ahead and wiped them down anyway. i left the outer burner cover off (shield with looking glass), and powered the furnace back up. it caught on the first cycle without issue and completed the heating cycle. it has since completed 4 cycles in a row without a hiccup. the procedures you outlined above are above me on the knowledge scale. i think i will defer to a pro if the condition persists. thank you for your help.

I am no expert, but this could be an intermittent exhaust ventilation problem. Something is causing the furnace to shut down. Condensing furnaces will do this if the installation procedures for exhaust vent are not followed.

I hope your installer figures it out. When he does please post the results.

mike_home, i have considered what you are saying, however the furnace has performed beautifully for the first 4 years. i had first starting having probs going into the end of last season, and now at the beginning/mid of this season when it's too cold for the heat pump. system is AmerStnd/Trane 2-stage furnace with UV, AprilAire 5000, humidifier, Honeywell IAQ VisionPro t-state, 16-seer AmerStnd Heat pump. i have wondered if there is an obstruction (animal?) in the vent. vent is on east side of house, with a prevailing north-westerly wind in the winter that sometimes swirls around towards the east side of the house which could result in a down-draft i suppose. i have noticed the condition, however, if it is calm or windy, so i have discounted that as a possible root cause. furnace is installed as updraft in the basement. vent pipe is vertical and then straight out the side of the house with a downward 90-degree elbow. here are some pics. (the galvanized flue is for the hot H2O heater, not the furnace).

The exhaust PVC pipe length seems short and this is no excessive amount of 90 degree elbows. Was a screen installed at the end of the exhaust? If it was I would remove it. The screen can ice up and restrict air flow.

I don't care for your air input. It should have been piped it to the outside also. I don't think that is causing your problem. It a poor installation practice.

Trane high efficiency systems are notorious for furnace problems. What you are most likely seeing is not a combustion fan failure, but a flame failure on startup. Check a couple of things:

• Your venting system could be plugged. During the Summer months, wasps, and sometimes even birds build nests in the venting. A venting problem will prevent the furnace from starting.
• Also check the vent terminations outside. You should either have a factory concentric vent termination or the air intake and the exhaust should be separate with the flue pipe termination pointed down. Check your installation manual for more info on that.
• Another possibility is that your flame sensor ( the little rod with the yellow wire) has become oxidized or dirty. Simply remove it and scrub lightly with a green scrub pad, not steel wool.

Hope this helps. If we can be of any service or if you need more information, feel free to visit our blog at Air and Energy Solutions.

mike_home, i will check the venting for icing. Air and Energy Solutions, i don't believe it has a screen, but maybe a waffle end. yes, we have lots of yellow jackets around the deck and pool that build some pretty big nests, so i need to check for any blockages once we get back into some warmer winter temps when the heat pump is running again (it's dang cold! -2˚F in ohio this morning!!!). ignitor and flame sensor are new, but i took them out and wiped/sanded them to a shine again anyway. exit flue is pointed downward towards the ground as per spec.

furnace continues to cycle as normal with zero misses on ignition of all 4 burners. i reinstalled the burner cover, but removed the looking glass. just that little bit of compensation has seemed to worked. so, i really think the culprit could be the venting. assuming no major reoccurrence of cycles being missed between now and spring, i think i will pull a chimney brush through the vent flue and run the additional pvc for the combustion air supply. i remember having a conversation with my installer on that, and i opted to use basement air for the supply. i plan to correct that. thank you all for your input!