Trane XE 90 pressure switch

There might be a Trane Technical Service Bulletin out on this problem.

Just wanted to say thanks to everyone for posting all the great info. I suspect my problem was strong winds as well, since we had them today. Simply turned the furnace off (using the main switch on the furnace) and back on - no good, but did that again, and it started working again.
Thanks!

my five year old XR90 is experiencing the same three blinking lights. It takes about three or four inducer cycles to get it fired up. The pressure switched was replaced and it ran fine for about a month and then began the three lights began blinking again. I can pinch the lower hose for about thirty sec to fire it up but it makes me nervous. My heater guy suggested I call the Trane specialist to look at it. I did check the intake and exhaust and they are clear (they come out on the side of the house) but on windy days it takes several cycles to get fired. I cleaned all the hoses and connections. I disconnected and cleaned the drain hose from the inducer assembly. I bought a new inductor fan assembly on Amazon, it's weird how they have it in stock, I suspect it's a common replacement item for $250 so I could be prepared for this weeks sub freezing temps. The Trane guy is coming out tomorrow morning. I wonder if he will say he never saw this before.

I have now had to replace the flame sensor after cleaning it no longer helped. The blower motor gave out, which I believe may have been the starter circuit which caused the motor to heat up and wreck the bushings. The three light problem went away a week after a guy came out and put on a longer hose to the pressure switch (but initially it did no good.) I am afraid to leave the house for a week for this 3 blink problem that is solved by turning it off and on. If a person put in a timer switch that shut the furnace off twice a day, it would be much more reliable which means the design is poor.
My furnace is something like 5 years old, replacing a 40 year old furnace that was reliable but some experts claimed had a cracked heat exchanger.

Just an FYI to those of you having problems. I went through the same basic checks that many of you did...pressure switch, paper clip, check the flu lines to see if they were plugged, etc, etc.

When you've tried all the basic stuff (I even replaced my pressure switch with a new one (same model for $40 online) and it doesn't fix your issue, it's probably a cracked heat exchanger. Mine was cracked for over 2 years while I had repair guys out trying to fix it. In the end, the 20 year warranty covered the exchanger, but not the labor. I feel fortunate to have that done by a great service guy for $350. The problem NEVER returned after the heat exchanger was replaced.

The crack was right on the header of the heat exchanger...about 18 inches long and up to 1/4" wide. Note that the header is plastic. Go figure.

Hello lostpilot28. Congrats on the fix of your cracked heat exchanger. I had a the crack along with thousands of others. Your problem is not solved. The problem is wind. Your Trane will fail to light when the wind comes at a sufficient force "and" direction. When your furnace fails to ignite again, make sure you cycle the power to your furnace at the switch on your furnace, "not" the thermostat.

Hey lostpilot28, the Trane specialist came over and you are absolutely right, there was a four inch crack in the heat exchanger. They are replacing it on Friday along with the high limit switch on the top burner and rollout sensor, both of which they think have been exposed to excessive heat from the burners being fed by the air leak. How does the crack in the heat exchanger affect the inducer draft? About six or seven hours to replace, will be about $700. Also need a new upgraded green circuit board because of some intermittent operation. I bought one on Amazon, has anyone replaced this themselves? Is it pretty straightforward? The Trane tech said it was a weak spot in their brand. also said I need to get another intake vent added because the current ones don't supply enough incoming air for the furnace to breathe and caused it to run too hot, about 6 degrees hotter, doesn't seem like much. That will be my next project to manage. Thanks for all your help.

Well, I spoke too soon. Dealer called and said the replacement heat exchanger would not be available for 30 days, none in stock anywhere. Five weeks in the midst of the Seattle winter is a daunting prospect. $3500 for a brand new replacement furnace. will consider it because I have no choice, but will probably opt for a different brand.

Furnaceguy59 said:

Hello lostpilot28. Congrats on the fix of your cracked heat exchanger. I had a the crack along with thousands of others. Your problem is not solved. The problem is wind. Your Trane will fail to light when the wind comes at a sufficient force "and" direction. When your furnace fails to ignite again, make sure you cycle the power to your furnace at the switch on your furnace, "not" the thermostat.

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Well, I'd love to agree with you, FurnaceGuy...but it most definitely is fixed. The wind may be an issue for some installations, but it wasn't for mine. The final proof for me was to see the "before and after" of the digital manometer readings. The crack was essentially causing the pressure differential to not be significant enough to override the pressure switch. Makes total sense to me. Apparently, it made sense to my furnace, too, since it works great now.

karasdad said:

Well, I spoke too soon. Dealer called and said the replacement heat exchanger would not be available for 30 days, none in stock anywhere. Five weeks in the midst of the Seattle winter is a daunting prospect. $3500 for a brand new replacement furnace. will consider it because I have no choice, but will probably opt for a different brand.

Click to expand...

Sorry to hear about that, Karasdad...I had to wait about a week for a replacement heat exchanger. Hope you get your issue resolved soon. I'm thinking that Trane has a real issue with the plastic header on the H.E.

Thanks lostpilot28, I had a builder friend of mine come over to check it out. He said the Trane XR90 is a single speed unit that runs wide open at 120 ton BTU all the time; it's a basic contractor model for large homes greater than 5000 sq ft. However, the ducting design I have limits the intake and restricts air flow volume to through the burner causing it to run too hot and cracking the heat exchanger. Additionally the A/C cooling coil creates additional resistance to the air flow volume which exacerbates the temp situation. The Trane dealer was coming over to estimate the cost of adding more intake duct tomorrow. My builder buddy recommended his HVAC contractor who came over and recommended a York Affinity, a multispeed blower with automatic gas throttling and two stage heating, so it can sense the air flow volume and automatically optimize the performance to heat the house to 1/2 degree of the set temp. It too is a large 120 ton BTU unit but it can operate at lower air volume and also improve the AC performance. About $4100 installed, no change to ductwork. Rebuilding the old Trane was going to cost $1400 and five weeks so I scheduled the replacement for end of week. I am really excited about having good heat again.