Furnace Frustrations, For The Mechanically Impaired

You'd think this would be a "Proper" rant but I just can't muster up the rage.

Right up front I have to say, as much as I like machines and mechanical things I suck at understanding them. The current drama is the 4 yr old furnace an AC which I swear is a lemon. I've had the installing company out countless times and yet it craps out reliably. I should be livid, I should be having some seriously intensive prima-donna moments but I can't muster "the mad".

I just am resigned and stare blankly.
I also mutter inanities like "well parts come bad right out of the box" cause sometimes they do.
"I know this is a pita, but you know, isn't there a reason for all this?"
"Sorry to be calling again, but it's not fixed"

Frankly I sound like a moron. I understand the older furnaces much better. The thermocouple would burn out, a blower motor would freeze up. Bearings would wear out, you know....normal stuff.

This new THING is just a mystery. Have had three Pressure switches replaced, at one point the AC was running when the heat was on, a couple of days ago the problem was diagnosed as a faulty fan/limit and that was replaced. Woke up this morning to again, no heat.

I'd like to say "I CAN'T EVEN!!!" but I spent a bundle on this, it's not very old and as much as I'm usually alright with "camping in the house" making the best of it everyone is telling me I should be livid. Maybe I should be? But mechanical things seem to have a life of their own and they remain a mystery to me. Sometimes they work when there is no good reason for them to, and other times they just do their own thing.

At this point I'm up for suggestions.
The company is VERY reputable and all the parts are free and under warranty. They have been nice and accommodating. I just don't know what to do cause for the last two weeks, AGAIN, it's the cycle of it's working...24 hrs later or a couple of days later NOPE! It's NOT!

Am now thinking It may be best just to go out up on the hill and build a nice campfire.
THAT I can do. I even think I get wifi up there.
(sobbing quietly)

What brand? Gas or electric?

Yep. You've got Gremlins.

They like to eat ham sammiches late at night, so try baiting them out of any suspect equipment with a ham sammich, potato chips and a can of Busch beer placed approximitly 2.29407 feet from the unit. At about 12:35AM.

Then position yourself with loaded shotgun at the other end of the hall behind a makeshift blind of some sort. And then keep very still and quiet until you're confident they've all emerged...

a reply to: Caver78

There's not a microchip or onboard computer in the thing is there? If so its probably this, if not a faulty thermostat or sticky valve could be the issue.
I'm just guessing here, but I know this, the more complicated things are engineered the harder they are to diagnose let alone fix faults. Modern cars being a good example. Pfft

Well, not much for me to go on in your OP, but I have been making a living in this field for 21 yrs now, and from the sound of it the contractor should have figured this out by now. There is no good reason that 3 pressure switches have been replaced by anyone who knows what they are doing. Now I have actually seen 1 unit in all my time, that was, in fact, a " lemon", but that is very very rare. I would call another company for a second opinion because, at this point, I assume the labor warranty has expired. You should have a 10 yr parts warranty as there's not a unit on the market that doesn't, and any contractor can honor that. ( MAKE SURE your unit has been " registered" otherwise parts warranty runs out at 5 yr) Lol, I wish I lived nearby because I really want to look at it myself .

a reply to: Caver78

Lemme guess.
It's one of those fricken high efficiency models.
96% or some such.
Maybe with a heat pump...

Damn things are nothing but a temperamental nightmare.

Any money saved in energy is lost in up front cost and then maintenance.

a reply to: Caver78


Basically, we have to understand and accept (two different things) that technology is a crime against Nature. Murphy's Law says "if something can go wrong it will." So it follows that the more complex the technology the more likely it will fail. You cannot build enough fail-safe innards into a technological gadget to prevent failure.

I learned by direct experience working in a machine industry that the dumping of poorly designed equipment directly on the public is the manner in which many products are "tested" today. No need too many factory test, to query techs or the public about discovering of the poor equipment, you merely notice on your inventories how many of new, replacement parts you have to stock (and sell). Bad parts can be great economic incentives for some businesses.

a reply to: DAVID64

If it has pressure switches, it will be gas. Well technically most heat pumps also have high and low pressure " switches" but these are limits on the refrigerant circuit. From the context of the OP, I think it is indicating the vacuum switches on the exhaust.

Its a gas 925SA Bryant.
Installed 9/13

The last error code was marked by the HVAC tech as a 71, but the ongoing yellow led flashes are three fast, one fast which I keep seeing is a 31 code?

He had said something was getting too hot, so it's designed to shut off. Replacing the fan/limit thingy should have fixed it? Just did a "Hard reset" by turning the breaker on an off, but Nada.

Thank you for replying, furnaces are boring.
I did see that Carrier and Bryants have a "known issue" and service bulletins were issued to suppliers. But that didn't really help. I'm just frustrated I can't "Intuit" what the malfunction is altho I'm leaning towards a problem with the electrical current to the damn thing.

Of course we know how well women's intuition goes over with a mechanic.

a reply to: surfer_soul

If it is only 4 yrs old, there is definitely a board on it, and if it is ( heaven forbid ) a " communicating" unit it can get ugly fast. Carrier Corp and Lennox are famous for there difficulty in the HVAC service tech world.

a reply to: Caver78

Look beyond the expected. I recall a troubling problem once that no one could determine the cause of the problem. It turned out that it wasn't exactly the machinery, but a squirrel had gotten down the exhaust vent, blocking the flow and the machine was acting appropriately in its response.

a reply to: hvacguy

I will be suggesting that be looked at!!
and OMG!!! thank you for thinking about it at all!!

My big issue is that my DH did this for a living and I watched him many times go nuts trying to figure out what was malfunctioning as the units went more and more high tech. Since he passed I've been trying to remember things to ask, say, that are relevant. I suck at it.

Two techs they sent out were clearly of the "hit it and run variety" I've requested they not ever come out again. The third is a decent guy who spends the time to get at the root of the problem, but he thought he had it fixed Thursday evening.

Did another reset by turning thermostat off AND hitting the breaker, it'll do the usual, cycle thru three times trying to work then shut off. I'm getting hip to the pattern.

Both the intake and the exhaust vent pipes are clear, I made the tech stay on on Thursday while I made sure by using the shop-vac on "suck". Because of outside feral cat squirrels aren't a problem, but House Wrens would be the culprit. No evidence the vents were clogged.


Discussed replacing the computer board last January but there was a massive snowstorm and we didn't reschedule it cause the furnace kept working.

Yep...cycled three times and quit again.

a reply to: Caver78

Ok, I had a feeling this was a Carrier product. on the inside or possibly the outside of the furnace cover, there should be a list of the fault codes. I know you probably aren't interested in that, but it will at least tell you what the flash codes indicate. 31 indicates a pressure switch closed ( on) during initial call for heat. Is this by chance a 58MVP model #? Does it have a PVC ( white plastic) vent? or is the vent metal?

Sorry, had to run and look.

Vents are white pvc pipe that vent outside thru the wall.

Bryant model # 925SA

Error code three quick flashes then one flash, card on door says it's a 31 code.

It will cycle thru three times shutting off each time, then you have to hit the breaker, but it just keeps cycling then shutting off.

The AC unit is FC36B3XC1A
Whole house AC.

Could a bird have crawled in the exhaust and died in there? I've went crazy diagnosing furnaces and it ended up being that.

Find a vent if it's gas exhaust works toss in a good size thing that goes boomb than shove the old one back in

Old thing are not designed to fail

I'm on the opposite side at least heating unit wise. Ours is old and cranky its stuck in an area thats hard to get to. It's actually down in a concrete pit with a grate over it.We never service it,but when working it cranks it out. Right at the first signs on winter it decides to stop working.Granted we aren't the great white north, but it was starting to get cold overnight and we got our Mom with us. Guy came out and started the this is a really old unit etc etc but I politely reiterated we going to want this fixed,not get a new one. Turned into a week to get parts and though I thought the cost was high and wanted to research it more get an second opinion, I decided get it fixed from the first company however and was glad I we got hit with our first real surge of winter less than 2 days later.I supposed if it was just me I would have been fine with the ceramic disk heaters(those work great in a pinch) and waiting Its hardest thing to remember but have your heater serviced in the summer when you can its cheaper.

I'd also consider in the summer getting a second opinion, had a check engine light on my truck keep coming on every time Id take it in they would service it, at multiple different places many that do good work. Getting my car serviced one afternoon I just casually mentioned it to the service guy, he called it his tech,and said it's a clogged emissions monitoring filter valve took 5 minutes for him to clean it and no problems since, it was something that either nobody knew about because its fairly new and obscure, or there are many unscrupulous repair shops out there.

Regardless Ive found the less emotion when these things pop up the better,shady repair guys take advantage of that emotion. I always try and act like its no big deal and even if I go with the first guy that checks a situation out, I'll usually flat out say I'll be getting a second opinion almost immediately so they know their diagnosis will be looked at for a confirmation and usually dont tell the second guy that another service guy looked at it already either. Good luck just remember in hundred years nobody will give a flip

a reply to: Caver78

You have a high efficiency gas furnace. You also should have another 6 years of warranty if the installing company did their job correctly. Residential units come with a 10 year warranty as long as the proper paperwork is filed. Is your furnace somewhere easily accessible?

This is the sequence of operations for a gas furnace -
1- thermostat calls for heat
2- inducer fan starts
3- pressure switch confirms inducer fan is operating
4- igniter energizes
5- gas valve energizes
6- flame sensor proves flame
7- 60-90 seconds later blower fan initiates

If anything in this sequence is faulty, the unit will shut down. You mentioned a tech said it was getting too hot and they replaced the limit switch, if it is still getting too hot, it's likely to be a fan speed issue and not the limit switch. It also may be a faulty board given the numerous issues you are having. I looked up fault code 31 on your unit and it's indicating a bad pressure switch on medium/high heat. The pressure switch will need to be replaced, and the fan speed may need to be increased to resolve the limit switch issue.

Appreciating ALL the replies!!


Service guy was here.
Kept shutting off, so he disconnected intake vent blew it out twice, Once from inside, once from outside,then cut it no obstructions.
Checked the drainage, no water drops on the gas pressure switch, drain running fine, no back flow.
Connected everything up again furnace ran fine.
Put doors back on, furnace shut off.

Checked everything again with the voltmeter, everything good.
Turned it on an off multiple times.

The previous hole drilled in the inducer assembly was a "tad" sloppy and when it heated up looked to be collapsing just enough to reduce air flow. By sloppy I mean it a hairline crack on the pressure port, just enough it would close up marginally enough to trip the switch.

He heated up an awl to smooth it out and the damn thing is running fine.

Technical term was collapsed inducer pressure port.

Before anyone screams, I was charged 84 bucks for 1 just ONE service call altho this is the third time they were here this week. If the furnace craps out again the inducer assembly will be totally replaced no charge and there will be NO service charge. If that isn't it I will still not be charged for another call and the trouble shooting will start all over.

Vector-
I'm on my third gas pressure switch. Actually there are two and they come as a set. So I'm learning new stuff, cool!
Bryant as two codes with 31. The other is a 13. unless you saw it first come on? Yeah...thats what I said too!!!

Thank you for suggesting increasing the fan speed!!

This is something most normal people don't freak out over, but I spend my day at work dealing with old machinery that breaks religiously and have to do work arounds so coming home to broken stuff freaks me out. I can't think straight at the end of the day an really only have enough time to get a shower an grab some sleep. NOT the smartest tack in the box during the workweek. Plus I'm outta here at 5:30 am , can't use a phone at work, and don't leave till 5pm.
Really screwed on that deal. Can't get ahold of anyone ever.

It's been very welcome to hear about everyone else furnace issues cause it's at least something different!