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BillyHvac, Journeyman HVAC Tech
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Hi, Im trying to reset the limit on my Trane XE-90 furnace.

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Hi, I'm trying to reset the limit on my Trane XE-90 furnace. I know it's easy but I can't remember the steps. Any advice?




Is there a code saying open limit?



Customer: replied 6 years ago.
No. Though the indicator light is completly off, not blinking or anything.

I had a plumber re-glue a fitting of the venting's PVC fitting yesterday as it was leaking. Before fixing it, he cut the switch attached to the unit, which I believe turns off the blower. He turned it back on, but the heater's been blowing cold air. I checked the filter, and it was pretty clogged so my guess is when he turned the switch back on the limit automatically tripped - it's done that before when the filter's been clogged. If it's easier to talk me through it (and you're allowed to do this), please call XXX-XXX-XXXX. Thanks.


It would be easier verbally but the site prohibits email and phone in order to protect customer privacy.


Now....the only time the unit has no light lit is when there is no power to the control. Blinking and steady lit are the normal oprations and faults.


Since you have no light it leads me to believe no power is supplied to the control.


This can be in the power switch

The blower door safety switch

Main breaker.


If you had a 3 blink code for example it would say control has power but limit switch is open.


Here I think we need to back up and find where the 115v power is off.



Customer: replied 6 years ago.
The unit definitely has power. When you close the door, the blower activates. I tried resetting the main breaker. All works. There is something on the panel that talks about what it means when the light is out, but I can't remember what it is.

I'm pretty sure I just to reset the limit for this unit, but it's not obvious how this done nor do I have/can I find a manual for it. I'd like to go ahead and get instructions on how to reset the limit, if you know how to do it.

There are 2 different types.


1) the switches are small round recessed around the bnurner box area. There is a small button in center. Pressing the button resets if tripped.


2) on the front wall behind gas pipe and valve is a flat switch directly on the fron wall. All you see is the flat plate and 2 wires attached. The switch is inside the furnace and not visable. This is an auto reset. It should reset itself...but if stuck open...tap the switch 4-5 times and retry unit. If switch does not close it will need to be replaced.


To test, remove the 2 wires and touch direct together thus bypassing the switch.



BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22541
Experience: Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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Customer: replied 6 years ago.
Hmmm. You're going to have to help me here a bit.

By Burner Box, do you mean the inside the top door? Where the pilot knob is?

"On the front wall behind gas pipe" - is that inside the unit? There are two doors to the unit. The top one that leads to the pilot knob. The bottom one that leads to the blower and all the schematics. And the auto-switch that activates the blower when the door is closed. Also I"m not sure which two wires you're speaking of. We're talking about a Trane TE-90. Or, by its mfg. model number: TUC080C942AO

I thought it was fairly easy to reset the limit, but apparantly it's not? I can't imagine why anything would need replacing since heater was working yesterday and it's not today after the plumber switched off the blower. So... ?




The xe90 has a burner area where the flame happens. It is on the perimetr of this burner area that the roll out switch would be.


Here ia picture of the 2 switches. The 2 outer ones are limits..the center is roll out with reset button


I just verified the control. The light is on constant when powered. The following is the fault code arrangement.



When system lockout occurs, the gas valve is de-energized, the

circulator blower is energized at heat speed, and, if flame is

sensed, the inducer blower is energized. The diagnostic indicator

light will flash or glow continuously to indicate system status.

(System lockout will never override the precautionary features.)


If the sensed failure is in the system (external to the control), the

LED will flash in the following flash-pause sequences to indicate

failure status (each flash will last approximately 0.25 seconds,

and each pause will last approximately 2 seconds).

1 flash, then pause System lockout

2 flashes, then pause Pressure switch stuck closed

3 flashes, then pause Pressure switch stuck open

4 flashes, then pause Open limit switch

5 flashes, then pause Open rollout switch

6 flashes, then pause 115 Volt AC power reversed/Improper


7 flashes, then pause Low flame sense signal

Continuous flashing Flame has been sensed when

(no pause) no flame should be present (no

call for heat)

The LED will also flash once at power-up.

Customer: replied 6 years ago.
Relist: Answer quality.
The expert is trying to explain where to find the limit switch, and even included an image, but his description and image is not matching my unit features. Here is the mfg. model number for a more accurate answer: Trane TUC080C9420

This is the limit directly under the burner box


High Limit Switch - Trane SWT01612


The issue is till - the control will always be lit with power to it. Maybe a wire is off, pulled etc. But I assure you the control will be lit with power to it. The limit is as shown above. It just has shorter ends than previous picture. This part and information came directly from Trane TUC080 parts list.


I will opt out so the others can have a look for you.


I wish you luck.



What is the Status of the LED light ? On/Off or blinking
Customer: replied 6 years ago.

Do you have access to my dialogue with the previous expert? I don't want you to spend time going down the same path - it just might be something I need to call a technician in for an on-site visit. I'm almost at that point.
I have read the dialogue and agree that if the light is out the is no power. If you are certian there is power the board may be bad

Hello, My name is Lew and I will try to assist you along with my capable colleagues.

Frequently, there is a float switch located in the secondary drain pan under the furnace

(on the outside) that is responsible for breaking the control circuit in the event of

condensate water overflow.The condensate pump (if present) also has an overflow

float switch (integrally mounted).

(For whatever reason it opens), It has the ability to stop the furnace/A/C

process so that more water is not produced. Let's look for a pump that has been left

un-plugged from the outlet (from when the plumber used his saw/drop light). Perhaps

he accidentally kicked the float, affecting it's sensitive adjustment (if exposed on the

outside of the catch pan) and breaking the low voltage control circuit. Also if the outlet

is GFCI protected (push/test type) it could do the same thing. These may be more

likely happenings and fits with your description of: ("working fine yesterday").

Be sure you replace the door panel before you try to start the furnace again.

I hope this information helps you locate the problem.

If so, I ask that You ACCEPT/BONUS my answers and provide POSITIVE feedback

for my efforts, as You see fit. I will still be available to answer your questions if you

need me further.

Best of Luck & Thank You...Lew