# Trane XE80 worked yesterday - won't come on today



## how (Feb 26, 2011)

That loose wire from the door switch will probably put 120V through anything conductive if that door switch is depressed. This is a potentially dangerous situation to play with. Turn off the furnace breaker to check it further.
Does that loose line from the door switch have a spade terminal attached to it's end, is it stripped clean to be marretted somewhere or does it look broken? I assume that one line from the door switch gets it's power from the main power feed conection box. The remaining loose line that is connected to the door switch should be connected to L1 on the mother board (if it is now empty.) Without the door switch being reconnected to the board - nothing will operate on the furnace.


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## Houston204 (Oct 18, 2009)

You may be able to tighten that spade connector so it doesn't slip off again.










I don't see a low voltage fuse on this diagram.


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## flounder (Jan 14, 2012)

My door switch has one wire coming off it with a spade terminal. Terminal looks fine but I don't know where to connect it. Door switch has two prongs, one has no wire connected, the other has a wire connected to the switch but it isn't connected to anything.

Shouldn't the door switch have two wires coming off it? There is no loose wire that looks like it should connected to the door switch.


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## Houston204 (Oct 18, 2009)

http://www.homedepot.com/buy/electr...n-tools/non-contact-voltage-tester-93406.html

Someone probably bypassed the door switch. A non contact voltage tester will quickly prove if the board is getting power. It will not prove neutral.

If the breaker is not tripped, it is probably the transformer.


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## how (Feb 26, 2011)

It sounds like your door switch has been disabled. The door switch should have two lines connected to it. One is the direct power feed into the furnace and the other is from the switch back to L1 on the board. The idea is that all the power to the furnace is turned off when someone opens up the door and the switch is disabled. 
Your discription of the furnace is that it has no power. Look for a power switch for the furnace somewhere near the closest access door to the furnace area. It will usually look like a light switch but will be often located in a higher position. Check to see if your furnace breaker is on as well.


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## flounder (Jan 14, 2012)

The breaker is not tripped, that is the first thing I checked. Anyway to check without that tester?


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## Houston204 (Oct 18, 2009)

How has a good point with the light switch. It is common to find this switch turned off when people are storing their winter decorations and flipping off the wrong switch when they leave the attic.


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## flounder (Jan 14, 2012)

how said:


> Your discription of the furnace is that it has no power. Look for a power switch for the furnace somewhere near the closest access door to the furnace area. It will usually look like a light switch but will be often located in a higher position. Check to see if your furnace breaker is on as well.


I checked both of those. Flipped the breaker to be sure and the switch is up. Nobody has been up there to have flipped it off. Any other ideas? We don't store anything in the attic.


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## Houston204 (Oct 18, 2009)

I've seen a tech touch the power terminal with the fingernail side of his finger so the electricity would contract the muscle and cause him to break free if it was hot.

I prefer the tester or a meter.:laughing:


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## flounder (Jan 14, 2012)

I'll pass on the finger nail but I do have a meter. I also have a tester with a light and two prongs. What I do check?


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## how (Feb 26, 2011)

A 5 year old furnace will usually require an external shut off switch by code so that you could disable the furnace without endangering yourself in an emergency. If you follow the electrical feed cable for the furnace up to the ceiling, it will often then angle away in the direction of the on/off switch.

I obviously type too slow to keep up.


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## flounder (Jan 14, 2012)

how said:


> A 5 year old furnace will usually require an external shut off switch by code so that you could disable the furnace without endangering yourself in an emergency. If you follow the electrical feed cable for the furnace up to the ceiling, it will often then angle away in the direction of the on/off switch.


There is a light switch above it with a feed coming from the unit to the switch, then out of the switch to I'm assuming the breaker. The switch is in the up position.


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## ben's plumbing (Oct 6, 2011)

test to see that you have power to the juction box on furnace....if you do check at door switch..if you don't check connections in box...


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## how (Feb 26, 2011)

I can't tell you how many on/off switches I've run into that are upside down. Its worth a try to put the switch in the opposite position for a moment to see if you hear anything from the furnace.
Beyond that it's metering at the junction box for power and then moving forward into the furnace if you have power or moving back to both sides of the on/off switch and towards the breaker if the furnace junction box has no power.


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## flounder (Jan 14, 2012)

how said:


> I can't tell you how many on/off switches I've run into that are upside down. Its worth a try to put the switch in the opposite position for a moment to see if you hear anything from the furnace.
> Beyond that it's metering at the junction box for power and then moving forward into the furnace if you have power or moving back to both sides of the on/off switch and beyond if the junction box has no power.


Thanks. I'll check into it tomorrow. The switch position is up the same as it was when I initially went up there to see what the problem is. Nobody has gone up there to flip the switch. We don't store anything up there at all and I would be the only person to go up there. Wife says she didn't go up there so it has to be something internal to the unit.


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## how (Feb 26, 2011)

Actually I should have got you to try jumpering W & R on the thermostat connections on the furnace board first but I was distracted by the disabled door switch.
Your furnace will not do anything if your thermostat or thermostat wires have failed. Connecting W & R bypasses all of that and is worth trying.


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## Houston204 (Oct 18, 2009)

> I have nothing. No lights on the indicator light.


Check for 120VAC to the transfomer. If it is present, check for 24VAC on the secondary side.


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## flounder (Jan 14, 2012)

how said:


> Actually I should have got you to try jumpering W & R on the thermostat connections on the furnace board first but I was distracted by the disabled door switch.
> Your furnace will not do anything if your thermostat or thermostat wires have failed. Connecting W & R bypasses all of that and is worth trying.


I'll try that first. Do I unhook W at the controller and jumper W and R?


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## how (Feb 26, 2011)

Some boards have led's that are lit when there is no call for heat and others are only on when there is a call for heat. *If* the led was always *on* in your furnace before this trouble then jumpering R & W won't help. If you are not sure then it's a pretty quick test to try.
Turn the thermostat off. 
On your board on the furnace the various 24V thermostat lines connect to a line of screws. Take a short length of wire and connect the screw marked W with the screw marked R . This directly bypasses the whole thermostat circuit to fire up the furnace. If the furnace imediately starts up when this is done then you know that your problem is somewhere on the thermostat circuit.
If nothing happens then take the jumper wire off again and you are back to working that voltage tester again to see where the voltage has stopped.


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## Doc Holliday (Mar 12, 2011)

flounder said:


> I'll try that first. Do I unhook W at the controller and jumper W and R?


 
No, you can simply turn the thermostat (controller) "off" and jump up at the furnace control board. No wire needs to actually be removed from their screw terminal when you jump, not in the furnace or in the stat.


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## Houston204 (Oct 18, 2009)

Looking at the picture from the XE80 manual on post 3, a slow flash is normal. 
No LED = check power.


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## flounder (Jan 14, 2012)

Thanks everyone!! Turns out the safety switch above the unit was bad.


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## hvac5646 (May 1, 2011)

HHHmmmm that was interesting.


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## hvac5646 (May 1, 2011)

flounder said:


> Thanks everyone!! Turns out the safety switch above the unit was bad.



How did you find that to be the problem?


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## Houston204 (Oct 18, 2009)

This safety switch?


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## Baldrick (Jan 5, 2012)

Glad you figured it out, nobody thought to mention that there is a fuse on the board on these units. Can't believe no one thought to mention that even though it was not the problem. Any shorts in the 24v will break the fuse and you will have no led light on the board. Just saying....


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## Houston204 (Oct 18, 2009)

Refer to post 3.


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## Baldrick (Jan 5, 2012)

Every board used in an American Standard or Trane 80% or 90% plus furnace has a fuse plugged into the board...


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## Houston204 (Oct 18, 2009)

Trane and Rheem were slow to start using this fuse with their gas furnaces. I have replaced many transformers in those brands because of this.

The diagram does not show a fuse.


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