HVAC hair-pulling and WHYYYyyyyy?

[AJ Dual]

Whenever the call for heat comes, right after the glow ignitor lights the gas, the inducer/exhaust motor starts buzzing and it shuts off, making the furnace blink a code.

Fair enough. It's a cheapo Bryant low efficiency model that's 15 years old, and it's driven hard and put away wet because my house leaks like a seive. So I'm looking up some parts...

Why is the motor assembly alone about $80, but the squirrel cage and the sheet metal bracket and the motor as a kit $300 or more?

Is it the same reason why a dog licks it's butt?

[Brad Johnson]

You sure it's not something as simple as the start capacitor on the motor?  Try spinning it by hand when the heat call kicks on (if it has one of the handy-dandy little external knob-turny things).  If it kicks off then all you need is the capacitor.

Brad

[Monkeyleg]

I had those sort of problems with our 30 year-old furnace in Greenfield. It was usually some really inexpensive part around the ignition system. The spark plug, or a ground wire that would separate when it heated up, etc. When one little thing malfunctions, the furnace thinks it's being told to shut down.

Try to find a manual online for your furnace and check some simple things before spending money.

[AJ Dual]

You sure it's not something as simple as the start capacitor on the motor?  Try spinning it by hand when the heat call kicks on (if it has one of the handy-dandy little external knob-turny things).  If it kicks off then all you need is the capacitor.

Brad

No it starts great every time and spins fine for awhile. And I traced the wiring and  it does not have a start capacitor, unless it's on the controller board where it plugs into. And the only capacitors on there are the teeny tiny kind that one wouldn't think are a start capacitor. It's a 110V AC motor, like what would be in a blender etc. Not normally what would have a capacitor, so I don't think that's it.

And the inducer runs for about 90 seconds while the glow ignitor gets ready to ignite the gas. It then starts buzzing and it all shuts off and the LED gives the blinker code for 6 possible things related to the suction/draft sensor (moves fine), blocked exhaust flue. (checked, no dead birds this time) flame proving sensor etc. or messed up inducer motor voltage.

I had those sort of problems with our 30 year-old furnace in Greenfield. It was usually some really inexpensive part around the ignition system. The spark plug, or a ground wire that would separate when it heated up, etc. When one little thing malfunctions, the furnace thinks it's being told to shut down.

Try to find a manual online for your furnace and check some simple things before spending money.

I've fixed all those cheap things over the past few years. Replaced the flame proving sensor, the heat exchanger exhaust overheat sensor, and the house air 120 deg. overheat sensor too. So they're all new/good. Or I already know how to bypass them to trick the furnace into thinking they're okay, and not the problem.

So I'm down to it being the main controller board, or the motor.

I don't even want to look up how much the controller board costs.  

ETA... Good news at least. All my online research said to just get the $300 kit of all the parts together, because they're often all rusted shut and unable to come apart. One squirt of PB Blaster, and a little torque on the hex key and the motor is out of the assembly.

[Nick1911]

Paging Jim & 280...

I have a hard time thinking that your inducer motor is at fault, because it runs up until the gas valve opens.  Do you have a model # for us?

[AJ Dual]

Paging Jim & 280...

I have a hard time thinking that your inducer motor is at fault, because it runs up until the gas valve opens.  Do you have a model # for us?

It's a Bryant 383KAV or more specific a 383KAV042091. Throwing Code 31.

My gut is telling me it's the motor, that something in the windings, or bearings is going bad, and it takes a minute or two of continuous run to fail before the buzzing starts. The plastic flywheel and axle spin freely still, but the bearings do seem a bit gritty. I've also been bypassing the pressure sensor by holding it down once it sucks in when the inducer starts, so even if there's a suction failure, I think the controller board is sensing funky motor return voltage.

[280plus]

Is it the motor buzzing or something else? Place you hand on it and see? Very tricky problem to chase without actually being there. One thing that does come to mind is once the ignitor begins to glow the next step in the ignition sequence is energizing the gas valve to open. My thinking is POSSIBLY the gas vale is at fault and sucking up all the electricity when it is energized but only because it's the next step in the sequence and your troubles seem to start at about the time the valve should be calling in. The inducer motor is a "shaded pole" motor and has no capacitor. Put straight 24V to the valve terminals (making sure you are connecting to the CORRECT terminals) and see if it opens. if it does don't let it go too long because now you're pumping raw gas into the furnace. A way to check the motor would be the same. Plug it straight into 110V alone, let it run and see if it starts to act up after a few minutes. If not look elsewhere. Let me know how it goes.

[280plus]

Another thing to do is disconnect the gas valve from the control circuit, call for heat and see if the same problem occurs with the valve out of the picture.

[Harold Tuttle]

Mine did that and I eventually noticed the PVC flue had stretched down on the woven strap, 2 inches, causing the condensant not to drain out. A flat washer and a wood screw was a permanent fix.

[Jim147]

Try it like 280 said. Unhook gas valve and call for heat. It should try three time to light before it locks out. Or put straight power to the inducer.

And check for what Harold mentioned. You can only push against a pipe full of water for a little bit.

I replaced one Saturday that I had to get the assembly for because it is a molded plastic housing with the wheel pressed to the shaft.

That's how they get you.

jim

[Jim147]

From the manual.

Component service test:

To initiate the component test sequence,shut OFF the room thermostat or disconnect the
"R" thermostat lead. Briefly short the TEST terminal to the ’Com 24V’ terminal. Status
LED will flash code and then turn ON the inducer motor. The inducer motor will run for
the entire component test. The hot surface ignitor, blower motor-heat speed, and blower
motor-cool speed will be turned ON for 10-15 seconds each

jim

[Jamie B]

Here is a link for the manual from the Bryant website(http://www.bryant.com/apps/finddocs/form.jsp?b=n)

http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/OM04-35.pdf


Here is some information that I googled for your code 31:

http://www.doityourself.com/forum/gas-oil-home-heating-furnaces/372722-bryant-383kav-led-code-31-a.html

[AJ Dual]

Good morning.

Just to clarify, this isn't a high-efficiency furnace, so there's no condensate issues with the heat exchanger. The exhaust stack is old-school metal and quite hot. (When it's running)

Well, a "watched pot never boils" applies here. I re-assembled the Inducer Assembly, and mounted it back on the Bryant to test out 280's suggestions. And now the furnace is running like a champ. It got down to 49 in the house, we were running space heaters, empty electric clothes dryer load with the vent disconnected back into the basement, and excuses to bake a lot of stuff in the oven just to keep it at that point... so the priority for right now for the furnace is to just keep it running and warm up the house.

So now I see two possibilities.

1. The motor's bearings. They're not exactly sealed, but non serviceable either. So, I lubed the bearing points on the motor as best I could anyway. I floated some Mobil 1 in there with a little PB Blaster to wick it in there. It does seem to be running quieter. So to me, that means it was the motor. And it'll probably fail again sooner or later because I'm sure my temp lube job is not going to be adequate. This'll be an easy enough fix since I'm now familiar with taking apart the Inducer Assembly.

2. It is the gas valve solenoid assembly like 280 suggests, but with the furnace being off and "resting" for 10 hours overnight, it's working again for now.

Although, I'd think, that the longer the gas valve solenoid is held open during this long call for heat that's going on, and the longer it keeps running fine, the more likely it is to be the inducer motor.

Am I off-base on thinking this?

[Nick1911]

Although, I'd think, that the longer the gas valve solenoid is held open during this long call for heat that's going on, and the longer it keeps running fine, the more likely it is to be the inducer motor.

Am I off-base on thinking this?

Probably.  For most gas valves, my understanding is that the hold open current for a gas valve is very low - it eats way more energy opening the valve then it does keeping it open.  The white roger gas valves on the carrier stuff we work on in the college often has a big coil to open the valve, and a little one to keep it open.

But yea, I could see it being crapped up bearings.  Usually, they won't even start at all in that case, though.  Cue the horde of inducer fan motors that refuse to start in the fall after sitting all summer.

[280plus]

My main question would be exactly what was buzzing? If it was the motor itself then you're probably on the right track.

[Jim147]

My main question would be exactly what was buzzing? If it was the motor itself then you're probably on the right track.

And if it was the motor, I'd have another one for that cold Saturday night it might decide to go out.

Too bad it doesn't use a Bryant HC608001 inducer motor. I have two on the shelf and would make you a smoking deal.

jim

[AJ Dual]

Update:

Furnace finally crapped out again. This time it was not lighting gas or letting any out at all. The inducer spins up, the glow-ignitor lights up, and then it clicks and lets out no gas. Then the inducer spins up again, and it now just does this over and over, never throwing a code at all.

Then I got a code 24, the 3 Amp 24V automotive style fuse blew. Replaced that, and it's just looping like the above again.

[Azrael256]

Detcord?

[280plus]

Sounds more and more like the gas valve. Hopefully you have a meter capable of reading 24 volts a/c. First take a reading off the gas valve terminals while it's running the sequence. If it gets 24V right around the time it clicks with no gas then it's definitely the valve. if you get some reading lower than 24V disconnect the control wires and (assuming there are only two) take a reading from those while disconnected and see if you get 24V. if you do, it's the valve. last check, power the valve straight from the transformer. Does it start sending gas through? No: it's not the valve, Yes, look elsewhere. Don't let it go too long if it does. We don't want you yo blow up.  Well, I don't anyways,

[AJ Dual]

Sounds more and more like the gas valve. Hopefully you have a meter capable of reading 24 volts a/c. First take a reading off the gas valve terminals while it's running the sequence. If it gets 24V right around the time it clicks with no gas then it's definitely the valve. if you get some reading lower than 24V disconnect the control wires and (assuming there are only two) take a reading from those while disconnected and see if you get 24V. if you do, it's the valve. last check, power the valve straight from the transformer. Does it start sending gas through? No: it's not the valve, Yes, look elsewhere. Don't let it go too long if it does. We don't want you yo blow up.  Well, I don't anyways,

I shorted 24V to the gas valve directly, right when the surface ignitor glowed, and the valve stayed open happily burning jets as long as I kept it touched to the extra 24V source that is in the circuit board's row of screws where the thermostat wires go. So the valve was good.

As far as I can now tell, it was the controller board. I guess I shouldn't be shocked it was about 15 years old. Got a replacement for discount cost by name-dropping a relative's HVAC employer and their PO number.

It's been running like a champ ever since.

[280plus]

Awesome!