From last November thru the end of January, we had all kinds of problems with our Trane XR90 furnace, which resulted in it shutting off and flashing an error code indicating a “pressure switch error”. These issues seemed to be corrected after the last service call at the end of January where the technician lowered the gas pressure and increased the fan speed to reduce the heat buildup inside the unit. Since then, everything has been working great, until a couple of nights ago when we noticed that the furnace had been running for a long time and was blowing cold air. When we went upstairs to look at the unit, it was blinking twice, which means “external lockout”.

We tried shutting the furnace off at the thermostat, but it didn’t respond. Flipping the power switch in the furnace closet and then turning it back on seemed to fix the problem. The furnace kicked back on and it has been blowing hot air ever since.

After a quick Google search, it sounds like the “external lockout” code could be caused by the flame sensor needing to be cleaned, or it could also be because our gas pressure is too low. It seems like we just can’t win with this furnace! We’re really hoping that this was just a fluke – neither of us are too excited about another round of service calls.

After about three months of service calls on our furnace, we think it’s finally fixed!!! The service tech started by replacing the motor that failed a couple of weeks ago, but that made no difference. We were able to run the furnace again, but after about 40 minutes, the furnace shut off, flashing the pressure switch error code again.

A couple of visits later, he asked us to run the furnace for a few days with the front cover off of the unit. Since it’s sealed combustion, he said it wouldn’t cause any problems and it would allow the unit to vent better. Without the front cover, we couldn’t get the furnace to duplicate the problem.

Once we figured that out, the service tech came back to look at a few more things. He wound up calling Trane technical support and running a bunch of diagnostics on the furnace. They couldn’t find anything wrong with it except that the gas pressure was a little high. He lowered it so the furnace wouldn’t burn so hot and then he increased the fan speed to move more air thru the unit. The combined effect is that there isn’t as great of a heat build up inside the unit. After making these adjustments, we’ve been able to run the furnace with the cover on for several days without having any pressure switch errors!

The only downside is that the furnace seems to be running a lot more. We aren’t sure how much of it is because of the recent cold snap and how much is caused by the lowered gas pressure. Hopefully we’ll find that the furnace runs much less next week when the weather warms up a bit.

We had another visit by the service technician today to try to diagnose the cause of the pressure switch errors on our furnace. The problem had been getting steadily worse over the weekend, with the below-zero temperatures forcing it to run for longer and more frequent cycles. We had problems several times where we were unable to get it to turn on at all … something slightly different from our previous experiences of being able to reset the unit at the thermostat to get it going again.

Today, the furnace was actually having the problem when the service tech came and he was able to quickly diagnose the cause of our frustrations as being the motor that drives the fan responsible for pushing the exhaust out of the system. He said it was hot to the touch and not working properly when he tested it with a volt meter. His thought was that the furnace has probably been experiencing the same problem with the motor overheating and shutting off, setting the pressure switch error code, since the start of the season, but with the extremely cold temperatures over the last few days (and with us attempting to reset it to get it going again), the motor had finally burnt out completely.

The part we’ll need is going to run about $330, but should be covered under the furnace’s warranty since it’s only about 3 years old. The labor to install it (he’s estimating around 2 hours) will be billed to our home warranty. Bad news is that the part is special order and won’t be here for a couple of days. With the furnace completely out-of-commission now, it’ll be a cold couple of nights on the second floor. Guess we should just be grateful it’s not the only one in the house or the situation could be much worse!

Last Thursday, we had the 4th service call on our furnace since last October in an attempt to fix the problem that’s causing it to flash the pressure switch error code. This time, we had a different technician come to look at it and he had some new ideas on what could be causing the problem.

He started by cleaning out the trap in the drain. Since this had already been done on the first service call last fall, only a small amount of nasty-looking gunk came out of it and it wasn’t as blocked as he’d expected, so this was likely not the cause of our problems. He then tested the drain itself by pouring a pitcher of water down it to make sure there were no backups. Since the drain accepted the entire pitcher with no problems and that’s more than the furnace would ever drain, he ruled that out as well.

According to this technician, a pressure switch error could be caused by a blockage in the intake, exhaust or drain. Since he thought he’d heard water backing up in the furnace when he first turned it on (something that’s not supposed to happen) and the drain appeared to not be the problem, he proceeded to investigate the intake and exhaust to see if there was a problem there.

Next, he looked at all of the PVC piping for the intake and exhaust to make sure that everything was sloped downhill so there would be no place for water to gather and pool. Finding nothing that looked suspect there, he then took a sawzall to the exhaust pipe, cutting it in half so he could look up and down it with a flashlight to see if there were any obstructions. Had a bird built a nest in the exhaust pipe, it could be blocking just enough air flow to cause the pressure switch to flip. Unfortunately, though, there were no obstructions in that pipe, so it seemed to not be a problem.

Since the tech wasn’t able to duplicate the problem and the sound of water backing up in the furnace didn’t appear to be happening any more, he was having some trouble pin-pointing the cause and left our house on Thursday with the intake unhooked from the furnace so that it would draw air from the room rather than outside. The idea was that, if the furnace didn’t have the problem while the intake was unhooked, we would wait several days, reattach it, and if the problem returned, we’d know the blockage was in the intake. If the problem occurred even when the intake pipe was detached, then we’d know we could rule that out as the cause.

Less than a half hour after the technician left our house, the furnace shut off again, with the light blinking 3 times, indicating a pressure switch error. Since then, we’ve had the problem numerous times. Last night and again this afternoon, it’s been so bad that we haven’t been able to get the furnace to come on at all.

According to the technician, the next steps will be to replace the pressure switch itself and then get Trane technical support on the phone to walk him through some diagnostics on the furnace to see if they can determine the problem. At least there’s a plan going forward … I just wish it were a more obvious problem!

An interesting side note: the technician commented on the number of registers we had closed in the attic and said the recommendation is that no more than 15% of the registers be closed at any time. Closing more could result in the heat exchanger cracking, which wouldn’t be covered under warranty.

Back in November, we started having problems with the furnace in our attic. We’d wake up in the morning or come home from work and notice that the thermostat showed a temperature several degrees lower than what it was set at, but the furnace wouldn’t be running. We’d go upstairs to find a red light on the furnace blinking 3 times, indicating a pressure switch error. The furnace is relatively new – it’s a Trane XR90 model that the previous owner said they installed only about 3 years ago.

At the time, we put in a service request with our home warranty and they sent a local repair company out to take a look at it. He cleaned the intake and the problem seemed to go away for a while, but no more than a couple of weeks later, we had the same issue again. We had the home warranty company send a recall to the repair place and the same guy came out to take a look at it. Since the problem is so intermittent, though (the furnace resets itself after a set time and will then run again for a while before having the issue again), he was unable to determine anything. He told us when he left that he didn’t see anything wrong with it, but that we should call him back if we continued to have the same problem with it and he would “start replacing stuff”.

It wasn’t even 24 hours after he left that the problem happened again (off hours, of course). I should have called them back then, but we got wrapped up in other things and, long story short, we’ve been living with the problem for the last couple of months.

Last week, we were watching television upstairs one night when the problem was particularly bad. Normally, when we notice the furnace has shut off because of the pressure switch problem, we can reset it (either at the thermostat or by flipping the power switch in the utility closet) and that’ll cause it to clear the error code and start up again. Last week, though, we tried that multiple times and it would almost immediately shut off again with the same error code flashing.

So, I put in a call to the home warranty again, and they sent the same heating company out to look at it again. This time the guy brought reinforcements, but they were still unable to duplicate the problem. They wound up replacing the main circuit board (because he thought he heard it making a weird buzzing noise – technical, huh?) and, up until today, we thought that had fixed the problem. Tonight, when we got home from work, though, the furnace was shut off again, with the pressure switch error code flashing. We were able to reset it and it’s ran fine for the rest of the evening.

I put in another call to have someone come take a look at it, but I have very little faith that they’ll actually be able to figure out what’s wrong with it. The only thing we’ve noticed is that it seems to happen more frequently when it’s windy outside. Seems strange (and the furnace guy assures us that can’t possibly be the cause), but it is an interesting coincidence …

As if our as-of-yet unresolved problems with the upstairs furnace aren’t enough, Wednesday afternoon, we came home and smelled the aroma of natural gas in our basement. A quick test with some dish soap on a few of the joints on the gas pipe revealed that there was a leak in the elbow of the pipe that goes up to the dryer on the second floor and the furnace in the attic. Not knowing how big of a problem it really was, we called the gas company (who had previously fixed a leak for me several years ago in an apartment). They promptly came to our house, but said that we’d need to call a plumber because the pipe was just too inaccessible. In the mean time, they disconnected the run going upstairs and capped the pipe. Thus, the night before a long holiday weekend, we were left with no heat upstairs.

We dinked around with placing a service request through our AHS home warranty for a couple of days before we realized it would be the first part of next week that they’d be able to get anyone out. (I’m not entirely sure how it works, but they claim that fits into their promise to respond to all requests within 4 business hours and service them within 48 hours.) So, after spending a couple of nights freezing under a pile of blankets, we decided to ditch the home warranty and just call a plumber out of the yellow pages.

Enter the plumber that makes us swear we’ll never have his company back to do any work for us. He showed up yesterday (on overtime, of course) and spent a good hour and a half banging around on the pipes in the basement, cursing the position of the elbow that was leaking, before he came upstairs to tell me everything was reconnected and he was getting ready to test for leaks. While he ran out to his van to grab a bottle of dish soap, I noticed the overpowering smell of gas coming up the stairwell into our kitchen. It didn’t take more than 15 minutes before it had infiltrated most of the rooms in our house. When I asked him about it, he told me it was nothing to be concerned about … he just hadn’t shut off the gas service to the house before uncapping the main pipe to reattach the run to the upstairs. The pipe had been open for about 30 seconds, but he had his “hand over it for at least half that time”. The reason he didn’t turn the gas off before doing this: he didn’t want to have to relight pilot lights. Not sure what he thought such a dramatic drop in gas pressure would result in … the pilot light for the water heater was out when he left anyway.

In an attempt to make the situation better, he told us it was nothing to be concerned about – the smell is something they add to natural gas since it’s odorless otherwise. (Because that makes a difference when the gas has penetrated your entire house.) He also stressed that it just smelled so strongly because we have incredible gas pressure – somewhere around 5 lbs, he thought – guess it was a good thing he covered the pipe with his hand, huh? And, of course, it wasn’t as bad as it smelled … how’s that possible?

Good news is that we have heat throughout the house again, the house didn’t explode due to the plumber’s antics, 24 hours later, we figured out what was going on with the pilot light on the water heater (and it’s now re-lit) … and we won’t ever be calling that company again to do any plumbing work for us. Incidently, it sounds like the gas leak that started the whole thing had probably been there since the pipe was installed in the mid 1980s … ug.

The furnace repair guy came today to take a look at our upstairs furnace, which has recently decided to only work for a couple of hours at a time before giving a “pressure switch error” and shutting off. I guess it’s a little too early to tell if the problem is completely resolved or not, but so far, so good.

I’m a little embarrassed to admit that the issue appears to have been caused by leaves in the intake. Since our furnace (a Trane XR90) is only about three years old, we were relieved to hear that it wasn’t a mechanical difficulty, but it’s still a little embarrassing to have to call a repair person to come clean some leaves out! I asked him if there was any regular maintenance we should be doing to prevent this or if there was some kind of a screen or filter we should install, but he said no. Probably just securing his future income. :) I just wish we’d watched what he did a little closer so we could avoid the house call the next time. I guess we’ll at least know what to look for should it happen again.

This week was the first real cold snap of the year and our furnace has sadly decided it’s all too much to handle. The most frustrating part is that it’s an intermittent problem. We woke up one morning earlier this week to find that our bedroom was pretty chilly. When Chad went upstairs to investigate, he took the front panel off of the furnace and found that it was blinking “Pressure Switch Error”. (We still aren’t sure exactly what that means.) We thought we were going to have to call someone then, but when he put the panel back on, it started working again. So, we left for work, thinking that maybe it was just a fluke. But, by the time we got back home, it was broken again with the same error code flashing. This time, we just turned it off at the thermostat and placed a service request with the AHS home warranty that we got when we purchased the house (and thought we’d never use). Since then, the error code cleared itself, so we turned the furnace back on, it ran for a day or so, quit working again this morning, and now it’s functioning fine again.

The repair person is scheduled to come tomorrow afternoon to take a look at it. I just hope they’re able to figure out what’s been causing the problems since it seems to be so hit and miss. From what I’ve read online, it sounds like this is just the general error code that you’ll get for any of a variety of problems … I just hope we don’t have to spend the rest of the winter trying to trouble shoot it. At least we have another furnace that heats the main floor so we don’t have to worry about pipes freezing or anything … even though it does get a little brisk upstairs!