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Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3136
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
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Hi there, I have a Trane XE90 furnace/AC unit. While changing

Resolved Question:

Hi there, I have a Trane XE90 furnace/AC unit. While changing the filter last night, I had some trouble getting the front panel off, and the unit seemed to die.

Thinking the issue could be the door switch, I replaced that, but I still have no power to the unit, and my LCD thermostat won't come on either.

Could it be a blown fuse that's causing this? The breaker did not trip when the unit failed.
Submitted: 1 year ago.
Category: HVAC
Expert:  Tim H. replied 1 year ago.

Tim H. :

I will need to gather some more information before I can answer your question(s). Please provide all information I ask for as I am not on site and you, essentially, become my "eyes and ears". In some cases, I may require some readings such as voltage before I can provide you with a satisfactory answer. If you are not equipped to perform these tests, the ability to work through to a solution may not be possible. We always recommend all work be performed by a licensed professional. At the end of our dialog, you will have a chance to rate my service, but please wait until we are done and you have your answer(s).

Hi, I'm Tim and I'm an HVAC expert here to help answer your question(s). Please provide all the information I ask for since I'm not onsite. At the end of our dialog you will be asked to rate my service, but please wait until then and all your question(s) have been answered satisfactorily. Thanks for your business!

Tim H. :

Good morning

Customer:

Hi there

Tim H. :

Have you checked the switch on the side of the furnace? The breaker? If you push in the switch with lower panel off, are there any LED lights on?

Customer:

No lights at all.

Customer:

and I've checked the breaker

Customer:

the switch is just a plain old light switch, right?

Tim H. :

Yes

Customer:

I'll check it again, hold on

Tim H. :

OK

Customer:

OK, switch was in off position, and the condensate pump came on, but still no power to the thermostat display, and no movement in the unit

Customer:

pump came on when I turned it on (though for some reason it was wired to be in the "off" position)

Customer:

as on

Tim H. :

Did you check to make sure blower door is on tight? If it is, try taking the lower panel door off and seeing if the fuse on the control board is blown. Many furnaces have a blade type fuse.

Customer:

I think the fuse MAY be blown, but where would I find it on the control board?

Customer:

it's not apparent

Tim H. :

Many furnaces have a fuse like this on the control board. I don't have a model number or specifics on your furnace, but check and see if it has this type of fuse.

Customer:

OK.

Customer:

just trying to figure out where that might be on the board

Tim H. :

It may not have one. It would be sticking out and apparent (on the board) if you had one.

Customer:

OK

Customer:

doesn't appear to have one

Customer:

AND there was a red LED blinking

Customer:

and the thermostat seems to have power all of a sudden

Customer:

but when I depress the door panel switch, the LED goes out

Tim H. :

Are you there?

Customer:

Sorry, just ran down to see what it was doing

Customer:

so no fuse

Tim H. :

No fuse in the furnace?

Customer:

and when the switch is depressed by the door panel, it shuts down the thermostat which, when the red LED on the bottom of the unit is blinking and the switch is NOT depressed, has power

Customer:

no switch on the control board, no

Tim H. :

How did you hook up this new blower door switch?

Customer:

I cut the old leads and replaced them with smaller ones that fit the switch in question

Customer:

Gosh, i wish I could show you how things look via FaceTime or skype or something

Tim H. :

OK, there should be two leads that attach to the switch. Can you turn the power off and take those leads off and jumper (tie) them together thereby bypassing the switch?

Customer:

I can do that, yeah. Just a second

Tim H. :

OK

Customer:

OK that's done

Customer:

still just a blinking red LED at the bottom of the control unit

Tim H. :

Now turn power on and see if it works

Customer:

power is on

Customer:

that's why the LED is blinking

Tim H. :

Is there a code legend somewhere around that control that tells what that blinking means?

Customer:

I'll go down to the basement and take a look

Tim H. :

OK

Customer:

it's flashing, though without a previous point of reference, I can't say if it's "fast" or "slow"

Customer:

and the codes are "normal, no call for heat" if slow

Customer:

which I guess is the case

Customer:

and "normal, call for heat" if fast

Customer:

which I don't think is the case

Customer:

that said

Customer:

the thermostat is set to 74

Customer:

with the ambient temp at 76

Customer:

and the thermostat says "wait"

Tim H. :

So it sounds like your furnace has power and 24 volts. But the thermostat is "dead"?

Customer:

I was able to start the fan though

Customer:

not sure

Customer:

the thermostat is an LCD readout

Tim H. :

OK and it says "wait"?

Customer:

yes

Customer:

it's lit up

Tim H. :

That is the delay when in a/c mode

Customer:

and I can make alterations to the desired temp, etc

Customer:

and start the fan

Customer:

OK

Customer:

so what does that mean?

Tim H. :

give it 3-5 minutes

Customer:

OK

Customer:

will do

Tim H. :

Then it should work

Customer:

I put a wire nut on the two exposed switch leads

Tim H. :

OK, I just wanted to make sure it wasn't the new switch

Customer:

no

Customer:

I think the switch they sold me at the electronics shop isn't the same type as the switch I removed

Customer:

I think this one BREAKS the current when depressed, rather than the other way around

Tim H. :

Yeah, better to get an OEM replacement

Customer:

like a fridge light

Tim H. :

There are many sites that sell Trane parts

Customer:

Ebay, my man

Customer:

eBay

Customer:

rather

Customer:

so it seems like I was basically on the right track, just didn't have the right switch

Tim H. :

Yes

Tim H. :

Go to an HVAC site that sells Trane parts

Customer:

still waiting to see if it comes back on

Tim H. :

It takes a good 3-5 minutes

Customer:

K

Customer:

Ok, seems to be running now

Tim H. :

Great!

Customer:

so I should be OK with it jumped like that, but will want to put in an oem switch, right?

Tim H. :

Yes, OK to leave jumped for now

Customer:

Gotcha

Customer:

thanks, Tim

Tim H. :

Yes, good luck! Thanks you for using Just Answer and please don't forget to rate my service. (Bonuses are always appreciated). Feel free to post back with any additional questions.

Customer:

I appreciate it.

Tim H. :

Have a great day

Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3136
Experience: Experienced in all aspects of HVAC, both residential and commercial.
Tim H. and 4 other HVAC Specialists are ready to help you

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