Bryant Plus 90 strange behavior


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Old 02-27-09, 07:11 AM
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Bryant Plus 90 strange behavior

I heat with wood most of the time and our gas furnace runs typically a couple times a day to warm up in the morning. However, while away for a couple weeks last month, the furnace decided to become finicky and has been giving intermittent trouble ever since.

A few years ago, I had a service call for a stuck pressure switch, which we got loos and did not replace. No subsequent trouble.

I am looking for troubleshooting help to determine my problem.

When it goes out, I get a code 21 error message.
While running, it will intermittently cut the fan then immediatly power the fan back on. It will cycle thru this action a couple of times, no consistent number, and then quit.

By powering down and resetting I can get it to re-ignite.

It is providing ignition and heat, but intermittently quits.

I have a schematic inside the cover, I am competent with a multi-meter and figure with some help I can probably figure out what's going on. But, I've never fixed a furnace before. If needed I can post a short video to YouTube as the thing is pretty weird.

Any direction to start with?

Thanks,
Tom
 
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Old 02-27-09, 07:35 AM
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The Carrier 2-1 diagnostic code usually means a gas heating lockout.

There is probably another code flashing before it gets to the lockout stage. It would be worth observing and reporting on what that code is.

Also, I'd recommend sitting by the furnace and observing how the furnace shuts off and restarts with greater attention to detail. When you say the furnace is operating an then immedietely cuts the fan and then powers it back on again, it leaves me wondering whether the burner continues to fire during that time and if not when it is shutting off and turning on.

These are critical points of information. Observing and reporting on what is happening carefully and in detail would be helpful.

Also, does your furnace have a pilot light that is lit each time, or a hot surface ignitor that glows to light the burners?

The pilot type would have three narrow gauge wires going into the burner compartment that are red, green and white.
 
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Old 02-27-09, 12:44 PM
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Will report back with greater detail, thanks for getting me going in a direction. The problem is intermettent, so as soon as I can observe it, I'll post back.
 
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Old 02-27-09, 04:37 PM
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There are two common categories of intermittent problems ----

those that manifest themselves after a furnace has been running continuous for a lengthy period of time --- perhaps 45 minutes or an hour, and those that manifest themselves on a small percentage of the calls for heat --- perhaps 1% or 5% or whatever of the times the furnace turns on.

Yours is probably of the second variety.

You can probably get the furnace to fail by repeatedly cycling it through the ignition process, perhaps 20-30 times until it fails to operate properly. Cycling it repeatedly also gives you experience in observing the details of what the furnace does when it's operating properly, which will make you a better observer of what happens when it doesn't operate properly.

So you probably do not have to wait around for the furnace to quit on it's schedule. You can probably repair it on your own schedule instead.
 
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Old 03-13-09, 07:43 AM
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Guys,
I haven't blown off the request for help...just can't get the darn thing to repeat the problem. I probably have spent a few hours standing by waiting for it as it fires up...it's been working fine now.

Is there a way to run it thru ignition cycle from a the furnace? I have been running back & forth to thermostat.

Frustrating.

There is definately a problem.

I'll bump the thread if I can get more observation of the details.

Tom
 
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Old 03-13-09, 10:55 AM
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Generally speaking, using a jumper wire to connect the R and W connections at the furnace will turn it on. You'll probably find the thermostat wires connected between these terminals for that reason.
 
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Old 03-31-09, 10:35 AM
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You can initiate a full system test by shutting off the thermostat or taking off the R lead and then with a small wire, short across from the test terminal to the "Com" 24v terminal. It will then run through all of the system checks. By observing what happens you can get closer to what the problem might be.
 
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Old 10-12-09, 06:59 PM
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The heating season is back and I can't ignore my problem any longer.

I just spent the evening testing, cleaning and observing the furnace.

The limit switch and secondary limit are good, the pressure switch is operating properly. I

When thermostat calls for heat, the inductor cycles on, pressure switch closes (26-27 VAC) but ignitor is intermittent and so is the gas valve opening.

Last 10 tries, can't get past pressure switch closing - ignitor won't come on. I checked it for continuity / resistance and it came in good with 77.9 ohms resistance.

The furnace is always giving code 31.

I checked all the drain lines and the vent lines, all are clear.

I did get it to ignite but it only burned for a few minutes before going out and flashing 31. I did not clean the flame sensor yet, but, is that involved in getting the ignitor to glow?

I'll get it, but I need to figure out what's going on first. All replies welcome!!!
 
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Old 10-13-09, 01:57 PM
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When I run the diagnostic test, what should I see? While it's testing, it runs code 11 - no stored codes - but it doesn't appear to power up the ignitor.

Inductor and blower fans both run and when it's done, just a steady LED.
 
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Old 10-13-09, 06:16 PM
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Check connections at the board. Remove then reinsert. Check the ground wire connection also. If any pin-looking connections (as opposed to spade connections), see if any male pins look thinner diameter than some others. If so, spread the pin open a tad, and reinsert in female connection point. You can confirm by testing for current when it is supposed to be there, by testing on the other side of the connection. Last heating season I almost bought a new control board -and luckily I caught the bad connection before doing so. And have not had a call back since to that place, after I spread that pin at the igniton control module.

Test for 120 volts across the ignitor wires that come from the ignition control board.

And also test right at the connection points on the ignition control itself (you'll have to temporarily unplug the ignitor wires to test the terminals direct). Then wait for the ignition sequence when after say those 30 seconds when the ignitor should start to normally glow, see if you have 120 volts at the ignition control. Hold the test meter there long enough so you are certain that it was to have taken place.
 

Last edited by ecman51; 10-13-09 at 07:08 PM.
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Old 10-13-09, 06:47 PM
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Thanks for the tips, I'll check it out.
 
 

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