# Trane XE 80 High Temp Limit Switch



## beenthere (Oct 11, 2008)

Do you have central A/C. If so, when was the last time the indoor coil was cleaned.


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## BCS (Nov 4, 2013)

Yes central AC. Not sure when the coil was cleaned. Where would that be?


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## beenthere (Oct 11, 2008)

On an upflow furnace, it would be on top of the furnace.


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## BCS (Nov 4, 2013)

so not in the furnace near the burners, etc., blower, etc. But physically on the outside towards the top?


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## beenthere (Oct 11, 2008)

Yes, sitting on top of the furnace. Look for teh 2 copper lines that come from the outdoor unit. they run directly to the indoor A/C coil.


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## hvactech126 (Nov 11, 2010)

Does the blower run with a call for heat?


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## BCS (Nov 4, 2013)

hvactech126 said:


> Does the blower run with a call for heat?


Yes it does


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## BCS (Nov 4, 2013)

beenthere said:


> Yes, sitting on top of the furnace. Look for teh 2 copper lines that come from the outdoor unit. they run directly to the indoor A/C coil.


This is what I am seeing


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## BCS (Nov 4, 2013)

I realized that I might of missed the actual furnace filters. However, I've looked everywhere and can not see where it would be located. 

My furnace is up in the attic and the only filters I changed were the 3 in the ducts by the ceiling underneath. 

Should there be filters right next to the furnace? I dont ever recall changing those or the HVAC guy that came to service the furnace, AC, etc. He always changed the filters in the ceiling.

Is it possible that the furnace doesnt have a filter in the attic and due to the duct work, they are located in the ceiling for easy access and replacement?


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## BCS (Nov 4, 2013)

Here's a picture of the set up. 










When looking at the furnace straight on. This unit is to the left (next to the burners) and there is a lot of air that comes out of the top right hole in the picture. Could the filter be in there?


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## biggles (Jan 1, 2008)

trace the pair of wires from the hi limit switch remove from board and read the switch again thru the wires going into the hi limit switch O.OO is closed like having the two probes touching.jump the hi limit at the circuit board terminals and repower furnace and call for heat


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## BCS (Nov 4, 2013)

biggles said:


> jump the hi limit at the circuit board terminals and repower furnace and call for heat


 sorry, but what do you mean by this?

I understand to pull the limit switch out and use the existing wires going to the leads to get the reading on the multimeter, but from there, how do I jump the hi limit at the circuit board terminals?


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## beenthere (Oct 11, 2008)

The front panel where those copper lines are comes off. Its a few screws. Then you can access the coil plate behind it, an remove the plate and look to see if the coil is dirty.


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## BCS (Nov 4, 2013)

Coil plate was clean. I suspect its the board by now As the high temp limit switch is not open .


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## beenthere (Oct 11, 2008)

You need to remove the coil plate to see the inlet side of the coil. The plate can be clean when the coil is dirty.

You can try the board, but checking the coil cost nothing, and leaning the coil evn if it is not the real problem, harms nothing.


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