TRANE XE90 getting no power, no red light

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Nov 13, 2015
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I would like to start off by saying I'm not a complete dumbass, but I might have done a dumbass thing to my furnace.

Well, we just kicked on the heat for the first time this year and the furnace was blowing out cool air, probably more like room temperature air. I went down and looked at it this morning half asleep and cold without my contact lenses in yet and moved my high limit switch to where it threw a spark then my furnace quit blowing air. I went back to look at it a couple hours later, this time with my brain functioning. I checked the "blinking red light" so I could look up the code and the blinking red light is not blinking or coming on at all. I looked it up and the code is CHECK POWER. I flipped the circuit breaker off/on, it was fine, and went back to the furnace where I flipped the power switch off/on a few times. I noticed a very low humming noise like something is getting power. Just to be thorough, I turned off the thermostat and checked again. This time, as expected, there was no humming noise and still no blinking red light.

Right now, I have the thermostat off and will leave off for a few hours before checking again (is there a certain amount of time I should wait? I read to leave off a few hours so I'm trying it). If this doesn't do anything, any ideas? Thanks in advance! I will do some more searching in the meantime to see if I can find any ideas myself.
Update : Getting slow blinking red light! Going to check with thermostat. Will update in a few.
UPDATE #2 : OK, back to where I was in the first place. Finally get to see the code I am getting and I am getting 4 flashes, which means OPEN HIGH LIMIT DEVICE. I'll look around for this, but if anyone wants to chime in, you are welcome to! Thanks again for the great help! LOL
Welcome to the site.
I found this video. The hum might br the fan motor, but I am no expert on this stuff.
FINAL UPDATE : It was limit switch. Just needed to bang it on the concrete floor a few times to get it to work. It's an annual thing, so once I got power back, I figured I could figure it out.

Sorry Nealtw, didn't see your post. I thought I was the only one who replied. Thank you for your reply!
FINAL FINAL UPDATE (I HOPE :rofl:) : OK, it's NOW officially blowing out HOT AIR!!! For some reason, the gas valve switch was in the OFF position! :rofl: I guess I should have checked the obvious possible solution instead of "Pavlov doggin'" it! :agree:

Well, I'm back to getting no power to the furnace. Since the last time I chimed in, here is what has been going on.

1. About 2 months ago, I was getting 3 blinking lights, which is a pressure switch error. The furnace would try to start and quit. It would repeat this like 5 times before giving up for a while, then after a few minutes, it would go through this cycle again. I noticed the (intake fan?) was rattling and getting worse. If I would bang on it a few times, it would eventually quiet and the furnace would run. I did this until I replaced it.

2. Things were working fine until about 10 days ago when it would give me the 3 blinking light code again, but I could get it going again. It did this a few times until 5 days ago, the furnace died. It's getting NO POWER AT ALL! No blinking codes, no trying to start, nothing! Since then, I replaced the circuit board (no improvement), bypassed the door switch (took the wires off the door switch and connected them together with a piece of metal), checked the filters (they were cleaned a couple months back), checked circuit breakers which are fine, checked the power at the on/off switch on the side of the furnace and it IS GETTING POWER (it runs to a power outlet and I plugged in a lamp. flipping the switch turns the lamp on/off).

So it looks like the power problem is between the power outlet where the lamp is plugged in (last place I can verify power) and the door switch? (I'm guessing that would be the place power would run before the circuit board?) Like I said, I'm not an expert, but I am mechanically inclined and I don't want to go messing with stuff I don't know about without advice. So my question is, where can it be between the power outlet and the door switch, if that is correct? Also, would your solution target the pressure switch error?

Your outlet goes out when you turn the furnace off, Does the furnace plug in there too, If yes, move the lamp plug to the other side of the outlet, if it is wired in to that box, open it up and check the connections????
I would think the power would stay on the outlet, so you could have a split outlet with a problem.
First you say you have no power. Did you check with a volt meter or glow light ? When You open the bottom door there is a junction box , check there. Are wire nuts or connections tight?

Next , your trouble code . You have a high effiency furnace , it has a draft inducer motor. That could be bad , the pressure switch could be bad , the intake or exhaust vents could be obstructed.
@Neal, No the furnace doesn't plug into this outlet. The on/off switch runs to the outlet and nothing is normally plugged into it, but the top plug in works, but the bottom one doesn't. Hasn't since I can remember. There is also some kind of attachment on the bottom of the outlet that runs to the humidifier too.
@buffalo, can you post a picture of the junction box? Not sure what it is. And I bet the pressure switch is bad. I had some kind of problem with it in the past and hitting the switch is what got my furnace to kick on recently.
It's just an electrical box. Power from your electric panel goes into the furnace . Inside there is a box that ties your Rome wire in with your furnace wires.
I took some pics if this helps. Can you tell me what I need to look into?

#1 This is the outlet on the side of the furnace. The part attached to the bottom has wires leading to a condensation control.

#2 Is this the junction box on the inside where the outlet is?

#3 The pressure switch which I took down when I put the fan in.

#4 I got a new fan about a month ago. The old one was very noisy so I thought it was the problem.
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Here are some more.

#5 Upper area.

#6 Center area.

#7 Bottom area. I just replaced the control box.

#8 What is this small box? It's in the bottom area.
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So when you turn the breaker off for the furnace you lose power to that outlet too?
So turn off the furnace breaker and remove the cover pull the screws on the outlet and just pull it out so you can see how it is wired and wire colors, then open the box on the inside and see how those wire are attached in there.
The second set of pictures are not showing up??
I have an on/off switch that goes to the outlet.


I will try what you said and try to take good pictures or else let you know in writing. What do I need to do with this information? Or are you walking me through some steps to diagnose? The furnace has been running for years without any major problems and I didn't do anything other than change the intake fan and control box (3 times in the past 10 years, but this time, it probably didn't need changed).

Also, are the second set of pics showing up yet? In #8, is that the junction box? Well off to do what you suggested. I'll let you know the results soon! Thanks a million for the help!
You getting power to the switch and the outlet, and don't appear to have power at the furnace, so the simple would be to think with vibration some wire may have come loose.
Buffalo was thinking I think that you were not getting power in there and if the power goes thru the outlet box then you check both???
@Neal, I checked the ones I could get to and tightened everything up, but nothing was really loose. Below is what I did with pictures.

So turn off the furnace breaker and remove the cover pull the screws on the outlet and just pull it out so you can see how it is wired and wire colors




Here is what I have.

1. Coming into the outlet from the on/off switch are 3 wires, white, black, and green.
a. The white wire runs to the upper left side screw,
b. The black wire runs to the upper right screw,
c. The green wire runs into a screw cap, which runs into the hole in the back of the outlet into the furnace (junction box?). Inside the box, it is grounded with a small screw.
2. There are 2 wires, a white one running from the lower left side screw to the box at the bottom of the outlet, and a black one which runs from the hole in the back of the outlet from the junction box into box at the bottom of the outlet.
3. Finally, there are 5 wires running into the hole in the back of the outlet (that runs into the box inside the furnace). They are...
a. the green wire explained above in 1c.
b. a white wire which runs from the lower left side screw to the control box plug in "LINE-N" aka "E7"
c. black #1 runs from the upper right side screw to the door switch
d. black #2 runs from the lower right side screw to the control box plug in "EAC-H" aka "E18"
e. black #3 runs from box under the outlet to the control box plug in "HUM-H" aka "E28"

So now what? LOL