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Bryant 90 plus furnace wont fire.

tangled in wirestangled in wires Member Posts: 23
Hey everyone,

Their is a Bryant 90plus furnace that is aggravating me to death. It will not fire and I cannot seem to pin point the problem. The furnace is about 14 years old.

The control was giving me an error code of 31 - pressure switch, rollout, high limit, Failure. I checked the pressure switch found that it would not make and replaced it with a universal P.S. that I got from my Bryant retailer. Replaced pressure switch did nothing. Furnace still would not fire. I was curious so started doing some work.

Checked vents- open, checked the P.S  tubes running to the combustion chamber, inducer, and gas valve for cracks or damage they were fine. Inducer starts up with no problem

Condensate clean of debris, Cleaned the burner manifold etc

I jumped out the P.S and very quickly after the HSI began to glow and then the pilot lit rolled out shutting itself down again. I then restarted the furnace and jumped out both the limit switch and the rollout switch as well and the furnace did the same thing lit quickly with a bang and turned off.  Now I think it could be one of two things here a bad exchanger or a bad inducer motor as the pressure switch is not making. I am not concerned with the gas rollout as I think the homeowner played with the gas pressure and I am going to re- adjust when I go back over their.

So now my question is How to I check for a cracked exchanger or a bad Inducer motor. I have 120 volts to the inducer and the bearings are not stuck but my lack of experience with gas really is shooting me in the foot here....


  • JStarJStar Member Posts: 2,752

    Oh my!!! Put down your tools and turn that furnace off!! You are exercising EXTREMELY DANGEROUS practices by jumping out a limit. Walk away now.
  • heatpro02920heatpro02920 Member Posts: 991

    I would get a gas tech in there with you to show you where you are... at the pressure switch what kind of pressure do you have?

    Did the error code change when after you changed the switch, did you buy an adjustable switch?

    I have done service calls like this, I would start over, put the old switch back in, and start over, pull the 24v leads off of the switch, put an phm meter on, let the inducer run and make sure you do not get an infinity read,{you should get low reading} if you do get infin, then I would do what you did checking all the hoses and blower and take a pressure reading, if all is fine replace the switch with the proper switch.... If you still don't fire, you have to realize the chances you have 2 bad parts in one service call are 1-28 {them are numbers from my service logs, and I'll bet they include a couple where my techs accidentally replaced one of the wrong parts, truth is unless this thing was hit by electricity one part breaks and you get the service call, sure you may go there for a bad pump and find a weak transformer you don't want to leave, but the service call was for the pump} anyway... Now check the function {this is where being a gas tech helps} I turn off the service switch, and t-stat, turn on the service switch wait a minute and jump in the t-stat leads. Now

    the inducer starts

    then switch closes and completes its path through all the safeties, if all are clear

    then the HSI or ignitor {unless it has pilot of course} will activate

    Next the gas valve opens and starts the burner

    Now comes in the flame sensor, if it senses the flame it shuts the ignition if it doesnt is shuts the gas valve, it'll try to fire a few times if it doesnt sense the flame then you will be in lockout depending on which board the unit has...

    then your fan control turns on the fan blower, then the t-stat gets satisfied, then the gas valve shuts and the fan runs until the fan control hits low limit....

    So you need to focus on that order of events, in there somewhere you are missing something, changing parts and jumping out switches is a bad habit, I had a tech that worked this way, never used his meter, just a bunch of jumpers and after I retrained him {he had 17 years experience} I don't think he could sleep with out the multi meter, service calls are much faster and efficient if you meter the bouncing ball. Thats how I train the guys to check out gas units, a bouncing ball, tag the common on one side of the meter and work your way around..

    Most issues are within the first 3 steps, either the t-stat isnt calling, the blower isnt blowing, or a safety switch isnt reacting... And after you find the problem keep in mind its not always a bad switch, it may be working how its supposed to, and the draft may be a problem, or the fan unit, ect...

    When you go through the operation events, let me know where it stops, then I can help a little better, but with out it infront of me it is tough...

    Also keep in mind there may be nothing wrong with any switches or exchanger, ect, the board can be sending you on a wild goose chase, or it can be a bad connections, alot of them units have the little push connectors that I hate because they look connected and feel connected but aren't...

    Gas service is so much easier than oil but you send an oil tech and he may kill himself before the furnace ever lights...
  • tangled in wirestangled in wires Member Posts: 23
    heres some more info

    Thanks guys for the response

    J you are completely correct jumping out switches is not the smartest way to do work but at the time my meter was dead as I must have left it on by accident so I was really out of options. Just to clarify I only had the Jumpers on the rollout and the Limit and the P.S. during the TFI I was just trying to get the furnace to run, then I popped off the jumpers. Still that being said that is not usually how I work.

    Heat Pro let me elaborate so maybe you can help me get somewhere.

    I got the call originally from the homeowner because his condensate line going from the primary heat exchanger was leaking. That was simply a matter of re securing the line with a new clip. However I was concerned that the water might have dripped onto the board and sent it haywire. I popped the board out and saw no visible damage. It was just displaying the error code 31. Thus I cleaned out the condensate etc...

    Here's the sequence of operations the furnace went through-

    1. Jumped out t-stat

    2.  Blower turns on to pre purge the system for 90seconds

    3. Inducer turns on and runs trying to prove but eventually turns off and the board gives me an error code of 31- which is high limit, P.S, and Rollout switch.

    4. after inducer runs I jumped out the P.S. and the HSI igniter began to glow nice and cherry red the gas valve opened the burners lit. It  would then do two things- 1. it would do a massive rollout come on with a loud pop and shut its self off instantly. The second thing it did when I re-tried TFI the burner lit long enough for the Blower to come on. Once the blower came on the flame blew out.

    This is why I believe it could be a cracked heat exchanger. When I first got to the job, The Airflow through the unit was terrible. I pulled out the Filter and it was matted down with dog hair. It must not have been serviced in 5 years it was like pulling out a fur coat. With that much restriction I can imagine the Heat exchanger over heating with no return air to cool it and cracking. That is also supported by the one time the blower blew out the flame and the P.S. not being able to make. That all indicated to me a cracked heat exchanger. Plus when it fired you got a faint smell of exhaust.

    I am going to test the original P.S. today although I am positive it is defective as when you jump it out of the equation the unit runs and when you blow on it the switch doesn't make ( I know rudimentary testing but the best I could do without a meter). I unfortunately cannot get the manual for this unit so I don't know exact measurements IE how many ohms the P.S. should be reading I only have a general idea from previous jobs.  However it doesn't make sense that the other Universal P.S. that I got from Bryant wouldn't work either. And yes it is adjustable.

    Also I can rule out the high limit switch as if that was popped out wouldn't the blower be running to try and cool the furnace? 

    How does this sound for a plan of action.

    1. Test pressure switch- put a manometer on it.

    2. Test inducer for proper voltage and amperage

    3. Test flame rod it should be between 3-5 micro amps and give it a cleaning.

    4. Test continuity and ohms of HSI,

    I guess I will start from the basics and see if it is the P.S or it is a problem in the system that is causing the pressure switch to do its job and open.
  • Tim McElwainTim McElwain Member Posts: 4,434
    First of all are you a service man

    with training on HVAC equipment?

    If so why not follow a systematic procedure for troubleshooting using a meter which is much better than jumpers. Jumpers work when you have by use of the meter determined a point in the system such as an open switch which may or may not be holding the unit off.
  • Tim McElwainTim McElwain Member Posts: 4,434
    First of all are you a service man

    with training on HVAC equipment?

    If so why not follow a systematic procedure for troubleshooting using a meter which is much better than jumpers. Jumpers work when you have by use of the meter determined a point in the system such as an open switch which may or may not be holding the unit off.
  • heatpro02920heatpro02920 Member Posts: 991
    Im thinking its time to get a gas tech there...

    If this was an issue where the unit was locking out because of a cracked hose to the pressure switch or a flame rod needing to be cleaned, an oil tech could easily get by, but it sounds to me like your gas pressure is WAY out of adjustment, you may have a serious venting issue, and or a damaged heat exchanger (s)....

    I think you mentioned someone touching the gas valve, too many spoons in the pot ruins the soup, but I think its time to bring in a professional spoon that can put actual eyes on the unit...

    Time to call in a gas pro, you don't want to risk property damage, personal injury, or worse...
  • tangled in wirestangled in wires Member Posts: 23
    Called in a rep no real answer a little dissapointed.

    I took your guys advice and  I ended up calling in a Rep from Bryant to come down and take a look at the system. He ended up condemning then unit. He did not find any specific fault with the system much to my disappointment as I was pretty curious to what could be wrong specifically. He seemed to agree that it was most likely a problem with the heat exchanger due to the rollout. The man had a ton of experience and obviously that plays a major role in diagnosing most situations. But I wish that we did some type of testing as well. Because it was  14 years old the rep said it wasn't worth the money to really investigate the problem and he offered to replace the furnace and the home owner agreed to it

    I would have liked to have gotten a more concrete answer but I do not doubt his expertise. However I am now in a unique situation. after speaking to the homeowner he gave me some work I installed a very nice tankless water heater and did some plumbing remodel work. I have become friends with the homeowner now he is a very cool guy,  I asked him if some  weekend I could come over and look at his furnace another time just to see to try and figure out what is going on and he agreed.

    even if the unit is replaced I still think this would be a very good experience for me were I could learn a lot just by getting more familiar with the unit.

    I just bought a digital manometer and I plan on hooking it up to the heat exchangers and running the blower and look for a change in pressure.
  • tangled in wirestangled in wires Member Posts: 23
    edited May 2013
    error with post

  • tangled in wirestangled in wires Member Posts: 23
    edited May 2013
    Called in a rep no real answer a little dissapointed.

  • Tim McElwainTim McElwain Member Posts: 4,434
    What is your location

    in the country? I am asking because I may be able to guide you to get some training that would help you in the future.
  • JStarJStar Member Posts: 2,752

    It really sounds like a broken impellar on the inducer motor. Did you pull the inducer assembly to inspect it?
  • tangled in wirestangled in wires Member Posts: 23
    figured it out

    I know how frusterating it can be giving all this advice and never knowing what the problem was so I solved the mysterious problem for me while the homeowner who is now a friend was waiting for his new furnace to come in I fiddled with his old system and funny enough it was a simple problem... but I missed it.

    Jstar you got it though should have brought you there! 

    Here how it happened. It had just rained buckets and I mean 2-3 inches the night before it was crazy rain. I was heading to his house to continue some plumbing work I have been doing for him.  when I got into the basement were the furnace was their was a 1-2 gallon puddle under the furnace and the blower housing was soaked.  So being curious I checked the vents going outside and they were dry no water so I was kind of thrown off but I figured their was only one way for water to get in and that's through the vents especially. It was supposed to rain that night and we were replacing the furnace anyways so I cut the intake and exhaust and put buckets under both and went back the next day after it rained day to finish his plumbing system and their was water in the bucket of the intake air. I went outside and looked at the venting and noticed for the first time only because rain water was dripping from his roofing perfectly into his intake pipe. I never would have noticed this if I didn't see it dripping as  the vent was just barley pitched back to the perfect angle to allow the over hang of his roof to drip into it. It should have been snorkeled. I went downstairs removed the inducer and it was completely corroded this problem I imagine was going on for years and I was amazed it lasted so long.

    Conclusion: The inducer was not proving the P.S. as it was a corroded ruin lol.

    second conclusion im buying the proper tools and going to pursue academic learning even more.

    Thanks guys for the posts

    and TIm I live in MA so kinda close to you...
  • Tim McElwainTim McElwain Member Posts: 4,434
    Tangled in wires

    I am glad you tracked down the problem.

    If you are interested in some training contact me by e-mail at [email protected] and I will get you some information on our training classes.

    I look forward to hearing from you.
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