Please help with my Bryant furnace not working


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Old 11-28-10, 05:55 PM
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Please help with my Bryant furnace not working

I have a Bryant furnace, horizontally mounted. A few weeks ago, the first time we tried to use the heat, it didn't work. The error code was code 31, which means the pressure switch wasn't closed. I removed the wires from the switch and touched them to each other and it worked. So I replaced the pressure switch. Now it still doesn't work, and I can't even get it to work by touching the wires to each other. The vent was sort of blocked with a birds nest, but I have cleaned that all out. I have also pulled out the inducer motor to make sure there wasn't a blockage on that end. I have also checked to make sure the vent tube that goes to the pressure switch is not blocked, and it is clear. I am out of ideas. Can anyone help?
 
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Old 11-28-10, 06:11 PM
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A birds nest is certainly a good explanation for the pressure switch not closing. People can't resist replacing pressure switches even though there is typically only a 5% chance the pressure switch is the problem. Sigh.

Does the inducer motor turn on when the thermostat is turned up to call for heat?
 
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Old 11-28-10, 06:20 PM
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Yes, the inducer motor starts each time. But after about 30 seconds the error code starts flashing because the hot surface ignitor is not energizing.
 
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Old 11-28-10, 06:32 PM
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Inspect the hot surface ignitor for a crack, often outlined by a whitish powder. Or use a multimeter to check for continuity across the hot surface ignitor.

When the thermostat is turned up, the inducer motor should turn on. Once it comes up to speed the pressure switch should close. The next step of the ignition sequence is for the hot surface ignitor to turn on and get white hot, after which the main burner gas should turn on for 3-5 seconds.

Since the HSI isn't heating up, it should be inspected for defects.
 
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Old 11-29-10, 06:48 PM
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The hot surface ignitors (there are two of them) look fine, no cracks. I don't think the furnace is even attempting to energize the HSIs, because it is detecting that the pressure switch is not closed - based on the error code. My understanding is that if the furnace detects that the pressure switch is not closed, it will not send any current to the HSIs. Is that correct?
 
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Old 12-03-10, 12:57 PM
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We've been advised to clear out the intake to the burner compartment, but can't figure out what or where that is. ANY help would be appreciated.
 
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Old 12-03-10, 02:22 PM
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Ummm. I've never encountered a Carrier furnace with two hot surface ignitors. The engineers don't always consult with me before doing such things though.


What's the model number of the furnace, which you can obtain from the rating plate in the burner compartment?

Is this furnace vented with white plastic PVC pipe or metal vent pipe?
 
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Old 12-03-10, 04:03 PM
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There's 2 little disc-type igniters each the size of a quarter, one high and one low. There are 3 gas jets. It's a 373LAV and the vent to the roof is a metal pipe. There was a bird's nest in it, but we've cleaned that out.
 
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Old 12-04-10, 06:19 AM
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Help! Very confused by the advice I got.

I've been told to check to see if the intake to the burner compartment is blocked with leaves or debris. Isn't the intake to the burner compartment just the return vent? How could anything get in there?
 
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Old 12-04-10, 07:00 AM
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Until a Pro can get back...lemme see if I can help a bit.

Your burner area is separate from the return vent. Remember....the flames heat up a heat exchanger, which the air from your house passes through to warm up. You can't mix combustion air and conditioned air.

If you are checking operation with the cover off..you are providing plenty of combustion air. If it worked cover off...and didn't work cover on, then the intake combustion air might be a problem. See what I mean?

As I said...no Pro here...but seems like I remember posts about the tubes that connect to the pressure switch being blocked? Do you have any such tubes? OH...sorry...I see you checked that. Is it possible your inducer is just not getting up to full speed?

I know a tech would hook up his manometer(?) and verify enough airflow....not sure how a guy like you or me would.

Very odd that you can't bypass the switch as you first did to verify other functions.
 
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Old 12-04-10, 08:51 AM
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You have an 80% AFUE furnace so it draws the combustion air from the immediate area, I think you can ignore any instructions about cleaning the air intake beyond making sure the grille in the service panel is clear and that there are no leaves or such inside the burner compartment.

I also doubt that you have two hot surface ignitors, are you sure you are not confusing thermodiscs?

You stated that you cleaned the hose connecting the pressure switch but did you clean the nipple the hose connects to on the furnace or induced draft fan? These nipples will sometimes corrode inside to the point of stopping the airflow signal to the pressure switch. You need a small drill bit to clear the nipple.

If you "short" the two leads to the pressure switch too early in the starting cycle the logic board will interpret that as a stuck pressure switch. You need to wait until the induced draft fan is running before shorting the pressure switch.
 
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Old 12-04-10, 08:52 AM
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I have the cover off. Is there also some other airflow that needs to come in? People on another board have said that the intake to the burner compartment could be blocked or clogged. But I don't know what that means. What is the intake to the burner compartment?

You're right, I can't measure the airflow, but I disconnected the vent and I can feel air blowing through. I pulled the inducer motor and checked - it seems like the fins are OK. But maybe the fan isn't turning fast enough.
 
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Old 12-04-10, 09:10 AM
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Do you have this owner's manual? (pdf file) Owner's Manual

On page three is a picture of your furnace. The section at the bottom is where the combustion air enters and through the grille of the service door when it is in place. The "other" board is referring to a 90+% AFUE furnace that has a separate duct that brings in outside air for combustion, you do not have that separate duct so ignore that information.

Read through the manual, it gives a fairly good tutorial of how the furnace works in normal operation although it is slim on troubleshooting tips. Remember that you must have the main blower compartment door in place (or at least hold the safety switch in) or nothing will work. Be sure that you didn't inadvertently trip any of the safety switches near the burner and that you have the gas valve switch on if your gas valve has a switch.
 
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Old 12-04-10, 09:16 AM
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Thanks for all the information.
1) I still am unclear about what is meant by the burner compartment. Is that the entire area where the inducer, gas control valve, pressure switch, etc is? Or just the smaller area where the burners ignite? I don't see any debris, but maybe I need to focus on a particular area.
2) Maybe I don't understand what a hot surface ignitor is? I thought it was the two silver discs that get hot which causes (?) the gas to ignite.
3) I will try to clear out the nipple on the furnace side.
4) I will also try to short the pressure switch later in the cycle.

Thanks very much for the explanation about the air intake. Is it also correct that my furnace does not have a "condensate discharge trap". I was told to clear that out, but I can't find it, and I think that perhaps it only exists on high-efficiency models?
 
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Old 12-04-10, 09:46 AM
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1. The entire compartment. If you don't see any debris then you are fine.

2. Check this page to see what you r ignitor probably looks like. You will need to scroll down. Ignitors To see what a thermodisc looks like check these links: Thermodisc

Thermodisc

Thermodisc

No, you do not have a condensate trap on your furnace. These are only found on the 90+% AFUE furnaces.
 
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Old 12-04-10, 09:46 AM
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I do have that manual. I understand now that air flows through the grille on the service door, and since I have the door off, there should be plenty of air?

I am using duct tape to keep the safety switch in. The "error code light" is on steady. I definitely have the gas valve switch on.

What safety switches are there? I see reference to the manual reset limit switches, which is part of what I was calling the hot surface ignitor, but maybe they are really called thermodiscs? I have pushed on them, but they don't seem to really move, just sort of wiggle a tiny bit.

Maybe a safety switch is engaged, so nothing will happen until I reset it?
 
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Old 12-04-10, 09:51 AM
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Turn off the power to the furnace and wait for a minute before turning it back on. This will reset any "soft" lockouts on the logic board. Be sure that your thermostat is set high to ensure a "call for heat" signal to the furnace. Make sure the blower door switch is pressed in all the way by the tape, it only has to come out a bit to shut off.

Do you have a voltmeter and know how to use it?
 
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Old 12-04-10, 09:52 AM
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I think I'm more confused than I was before. What are the flat silver discs, about the size of a penny, that glow orange when the furnace is working properly. right near the burner?
 
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Old 12-04-10, 09:57 AM
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I have been turning the power off each time the furnace has failed to ignite, and then turned it on before the next time I tried. That has varied between 5 minutes and overnight. The thermostat is set to 72, and the actual temp is 64. The tape seems pretty tight.

I don't have a voltmeter. My friend came over with one the other day and measured 19.3 volts across the pressure switch.
 
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Old 12-04-10, 10:02 AM
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Look in the area where the vent pipe exits the furnace, may be a thermodisc vent safety that is tripped due to running the furnace with an obstructed vent. Not all furnaces have this safety switch. A model number would help.
 
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Old 12-04-10, 10:25 AM
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I'm going to leave you in Skip's capable hands and maybe some of the other members can help. I need to go make some pancakes.
 
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Old 12-04-10, 10:43 AM
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My friend can come back with the meter if that would help.
 
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Old 12-04-10, 10:50 AM
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I don't see one right off. I have a Bryant 373LAV.
 
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Old 12-04-10, 11:11 AM
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There is only one hot surface ignitor in the furnace. It's below the burners on the right hand side and has two wires going to it.

If you have something else glowing.....

maybe that's the problem!



The manual I found is at:

http://www.gogeisel.com/geiselonline...CAV_Gas_OM.pdf
 
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Old 12-04-10, 11:38 AM
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LOL, SeattlePioneer! No, I was wrong, the discs do not glow. I bypassed the vent blockage switch and got it to work!!! I do not know how to reset the switch (I tried to push down on a tab I found there, but it didn't do anything). Do I need to buy a new switch?
 
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Old 12-04-10, 11:45 AM
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Yes, that switch has a manual reset. It should be pretty obvious and it typically gives a click when it resets. Often it's a little push button with a red dot on the place to push.

It would be unusual to have that fail, but anything is possible.

It is a safety switch, so I wouldn't by pass the switch to operate the furnace and I'd use a factory part to replace it if need be.
 
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Old 12-04-10, 12:00 PM
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I seem to have reset the vent blockage switch by pressing the tab on it. It's running good so far!

Everyone's help is much appreciated and I hope I can take this experience and help someone else out in the future.
 
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Old 12-04-10, 02:39 PM
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I'm glad you got it working and thanks for letting us know.

...I hope I can take this experience and help someone else out in the future.
Yup, you're on the hook now. Pay it forward.
 
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Old 12-04-10, 04:38 PM
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Skip Gets The Gold Ring!

Good suggestion on the vent switch!
 
 

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