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Old 11-15-2012, 01:51 AM   #1
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Intermittent Bryant plus 90 Start-Up Issue


Bryant plus 90 MOdel 398AAZ...

I run into a frustrating intermittent problem where my furnace has quit after any of the following scenarios:
1. When only inducer starts, then dies. System is locked up and I have to wait several minutes before turning the power off then back on again.
2. When inducer starts, then pilot lights up, system dies, then is locked up for several minutes before turning power off/on.
3. When inducer starts, pilot lights, main burners light up for about 5 minutes, system dies, locks up for several minutes before off/on.
4. When inducer starts, pilot lights, main burners light up, runs until the thermostat says to shut off, and then may run through multiple cycles before dying, requiring off/on.
The pilot burner was replaced last year. There is no obstruction in the incoming air vent. It appears the condense drain doesn't have any major water collection problems. Filter was recently changed.
Any ideas?
Thanks,
Paul

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Old 11-15-2012, 10:58 AM   #2
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Intermittent Bryant plus 90 Start-Up Issue


HI, I have the same problem with my carrier furnace, I did all the simple and obvious things first. This included removing the blower and blower wheel and cleaning the wheel in a tub of water with TSP, Removing the inducer blower and cleaning the intake and exhaust pipes, which are 3 inch PVC. (By the way, I cut the lines, blew them clear with my leaf blower and repaired them with 3 inch rubber fernco couplings. The leaf blower was my sons idea, and a good one) I also ran a new plastic toilet brush in where there was some residue in the secondary heat exchanger and cleaned it out thoroughly. My condensate trap coming from the secondary heat exchanger was clogged with crap and bugs and stuff. I cleaned it out with a solution of TSP and bleach. The idiot that installed my condensate drain used a cheap plastic compression coupling that leaked inside the blower housing. I replaced that with a glued standard coupling, as I wanted this to be water tight, and this is the first time all this has been done since the unit as installed in 93. I replaced the HSI and the pressure switch, cleaned the flame sensor, and replaced all the vacuum lines. I know, the pros are going to say I am guessing and throwing parts at the problem. They are right, but now I have a spare pressure switch, and an upgraded HSI.
After I did all this, I turned on the power and called for heat from the thermostat. Bingo! Everything worked perfect!..........once. The next call for heat the inducer motor started, I heard a clicking which I assume was the pilot solenoid in the gas valve, and then the HSI would not glow. I removed the control board, and looked at it closely. The back was coated with a fine black dust, and there were water stains on it. (Way to go Carrier, locate the motherboard under a hole directly below the condensate pan, and in the blower housing where dirt passing the filter can wash over it.) Geniuses. Built in obsolescence.

Well, anyway, I ordered a replacement control board with the exact same connections as mine, and I expect to receive it today. I also ordered a new gas valve just in case, as I got both for less than $200.00.

Now why am I doing all this? Simple.

1.) I am retired, and have more time than money. Also, I am positive that no HVAC tech is going to clean out my system like I did, and this is nothing against them, they have to make money fast for the boss.

2.) I like to learn, and now I know a lot more about high efficiency furnaces, and I will know even more by the time I am done.

Cost to date: $300.00. at the end of the day I will have my system in top condition for less than $400.00. A lot less than what I am hearing on these forums

As soon as I get the new board in and run diagnostics I will be back to you. BTW I am going to test my old board at the component level since it has through hole components which can be replaced. Nothing like a backup. LOL

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Old 11-15-2012, 11:05 AM   #3
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Intermittent Bryant plus 90 Start-Up Issue


Jagans, you're pressure switch is not closing if the unit is not igniting. Remove the pressure switch tube and use a straightened paper clip and clear both ports. On the draft inducer side it should be noticeabley clear so if it's hard, ram that clip through. On the pressure switch side be very gentle.

Sediment clogs those ports. Also, might want to check your exhaust pipes.
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Old 11-15-2012, 11:05 AM   #4
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And being retired doesn't make you God's gift to know it all-ism.
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Old 11-15-2012, 11:16 AM   #5
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Intermittent Bryant plus 90 Start-Up Issue


HI, I have the same problem with my carrier furnace, I did all the simple and obvious things first. This included removing the blower and blower wheel and cleaning the wheel in a tub of water with TSP, Removing the inducer blower and cleaning the intake and exhaust pipes, which are 3 inch PVC. (By the way, I cut the lines, blew them clear with my leaf blower and repaired them with 3 inch rubber fernco couplings. The leaf blower was my sons idea, and a good one) I also ran a new plastic toilet brush in where there was some residue in the secondary heat exchanger and cleaned it out thoroughly. My condensate trap coming from the secondary heat exchanger was clogged with crap and bugs and stuff. I cleaned it out with a solution of TSP and bleach. The idiot that installed my condensate drain used a cheap plastic compression coupling that leaked inside the blower housing. I replaced that with a glued standard coupling, as I wanted this to be water tight, and this is the first time all this has been done since the unit as installed in 93. I replaced the HSI and the pressure switch, cleaned the flame sensor, and replaced all the vacuum lines. I know, the pros are going to say I am guessing and throwing parts at the problem. They are right, but now I have a spare pressure switch, and an upgraded HSI.
After I did all this, I turned on the power and called for heat from the thermostat. Bingo! Everything worked perfect!..........once. The next call for heat the inducer motor started, I heard a clicking which I assume was the pilot solenoid in the gas valve, and then the HSI would not glow. I removed the control board, and looked at it closely. The back was coated with a fine black dust, and there were water stains on it. (Way to go Carrier, locate the motherboard under a hole directly below the condensate pan, and in the blower housing where dirt passing the filter can wash over it.) Geniuses. Built in obsolescence.

Well, anyway, I ordered a replacement control board with the exact same connections as mine, and I expect to receive it today. I also ordered a new gas valve just in case, as I got both for less than $200.00.

Now why am I doing all this? Simple.

1.) I am retired, and have more time than money. Also, I am positive that no HVAC tech is going to clean out my system like I did, and this is nothing against them, they have to make money fast for the boss.

2.) I like to learn, and now I know a lot more about high efficiency furnaces, and I will know even more by the time I am done.

Cost to date: $300.00. at the end of the day I will have my system in top condition for less than $400.00. A lot less than what I am hearing on these forums

As soon as I get the new board in and run diagnostics I will be back to you. BTW I am going to test my old board at the component level since it has through hole components which can be replaced. Nothing like a backup. LOL
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Old 11-15-2012, 11:24 AM   #6
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Intermittent Bryant plus 90 Start-Up Issue


Quote:
Originally Posted by jagans
Also, I am positive that no HVAC tech is going to clean out my system like I did
You're absolutely correct: a pro would have also checked and cleaned your secondary heat exchanger, which sounds to me like it needs to be checked.
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Old 11-15-2012, 12:12 PM   #7
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Intermittent Bryant plus 90 Start-Up Issue


You are dead right on that one Doc. I am learning every day, never said I knew everything, that must be your interpretation, Im just having fun. I realize that really knowing HVAC takes a lifetime of learning, and a lot of expensive tools.

Thanks for your tip, but I replaced the pressure switch with a brand new exact replacement and I tested it. The inducer motor is 120V AC so I put power to it directly, and with my multimeter set to continuity, clipped the leads to the two terminals of the PS. I got continuity as soon as the inducer motor spun up. I also made sure my intake and exhaust pipes are clear as a bell. All vacuum lines have been cleaned or replaced with new clamps.

Did I do it wrong?
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Old 11-15-2012, 12:26 PM   #8
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Benny, I did clean out my secondary heat exchanger. Didnt I say that in my original post? Yeah I did, I just checked. Anyway, yes I cleaned out my secondary heat exchanger by removing the inducer motor. I could not remove the plastic cover to which the inducer was attached because it was very solidly sealed to the Secondary heat exchanger with a curing type of sealant, so I had to work through the draft opening for the inducer motor. I used a plastic toilet brush, cleaned it out with soap and water, then shop vacuumed it out real good. I then used my seesnake to look inside to make sure it was really cleaned out. I cleaned off the old hard sealant and reattached the inducer housing with RTV Silicone.

Did I do it wrong?

PS sorry if you were insulted by the no tech would do blah blah blah, I guess a good one would, which you obviously are.

Last edited by jagans; 11-15-2012 at 12:28 PM.
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Old 11-15-2012, 01:20 PM   #9
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Intermittent Bryant plus 90 Start-Up Issue


Quote:
Originally Posted by jagans
Benny, I did clean out my secondary heat exchanger. Didnt I say that in my original post? Yeah I did, I just checked. Anyway, yes I cleaned out my secondary heat exchanger by removing the inducer motor. I could not remove the plastic cover to which the inducer was attached because it was very solidly sealed to the Secondary heat exchanger with a curing type of sealant, so I had to work through the draft opening for the inducer motor. I used a plastic toilet brush, cleaned it out with soap and water, then shop vacuumed it out real good. I then used my seesnake to look inside to make sure it was really cleaned out. I cleaned off the old hard sealant and reattached the inducer housing with RTV Silicone.

Did I do it wrong?

PS sorry if you were insulted by the no tech would do blah blah blah, I guess a good one would, which you obviously are.
A 19 year old Bryant that has never been serviced should have the rear of the secondary heat exchanger inspected, especially if the trap was plugged up and gunk was visible in the front of the HE like you stated. You can't see much from the hole where the inducer attaches, even with a seesnake.
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Old 11-15-2012, 01:39 PM   #10
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Intermittent Bryant plus 90 Start-Up Issue


It sounds like a bad board with all of those intermittent problems you are experiencing.

Good Luck.

Brian Martin

Last edited by beenthere; 11-15-2012 at 02:02 PM. Reason: removed link to company
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Old 11-15-2012, 05:46 PM   #11
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Intermittent Bryant plus 90 Start-Up Issue


The service guy came and cleaned out my condenser trap. Basically with a 20 year old furnace the trap became clogged restricting the drainage. If the drainage can't keep up, then the water backs into the pressure switch telling it to shut things down and lock up. We cleaned it out and it seems to be working fine. We'll see in a few days!
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Old 11-15-2012, 09:41 PM   #12
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Intermittent Bryant plus 90 Start-Up Issue


PulleyPS There is a response in here where Benny says that you need to clean out the rear of the secondary heat exchanger. Point is, you need to clean more than just the trap. I am sure he is correct. There was dry crap nearly blocking the plastic tube on the condensate pan of my secondary heat exchanger. I removed the inducer housing and cleaned out the pan as well as possible with a plastic bristle brush, water, TSP and a little bleach.

Drainage of the condensate pan was one problem, but I had a bad control board. I replaced that today and she is humming nicely now.

I learned a lot during this process, and I have a new-found respect for what it takes to be a GOOD HVAC tech.

It took me a lot of time to clean my furnace like it needed to be cleaned, and if good HVAC technicians go to the length I did, or like Benny obviously does, its a considerable amount of work.

It must be hard to explain to Joe homeowner why a good company needs several hours to do the job right as opposed to a clean the trap and run.

My furnace is running really good now, but I am going to clean the secondary heat exchanger this spring when I put in a new AC Condenser and evaporator coil. Ill inspect my heat exchangers really good to see if I need to bite the bullet and install a whole new system.

Last edited by jagans; 11-15-2012 at 09:44 PM.
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Old 11-15-2012, 10:26 PM   #13
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You may have a rotted out secondary.It is a very common thing with that furnace even if you think it's clean.
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Old 11-15-2012, 10:27 PM   #14
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Should be checked and may still be covered under carrier inhanced warranty program.
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Old 11-15-2012, 11:32 PM   #15
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Thanks hvactech,

The service guy did say that... that if there are still problems the next place to look is the secondary heat exchanger. But a preventive clean would be good.

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