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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a XE90 Trane and it is blowing cold air, 't know why.

Customer Question

I have a XE90 Trane and it is blowing cold air, don't know why.
Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
Red light is flashing 4 times then pause....4 times then pause.
Expert:  Daniel Plourde replied 1 year ago.

hi i am dan i can help you with this. that error code means the high limit switch is open and that is why it is not letting the burner come on. can you locate the high limit switch in the furnace?

Customer: replied 1 year ago.
I can find it but I checked its continuity and it didn't seem open. My ohm meter showed that current could flow through it but I still get the 4 flashes.
Expert:  Daniel Plourde replied 1 year ago.

the best way to check it is with the power on and testing voltage. you should read 0 volts across it and 24 volts from one terminal to ground.

Customer: replied 1 year ago.
Those are normal readings if it is working properly? It's the one with the little red push button right?
Customer: replied 1 year ago.
Any idea how much a new one cost and where i can buy one?
Expert:  Daniel Plourde replied 1 year ago.

no that is the roll out switch. it may be tripped instead if you push that button in that will reset it and see if that works. if not it is the high limit switch that will have 2 wires coming from it and be mounted on the plate of the furnace sticking inside it. if you can take a picture of the furnace with the components and post it here i can help you locate it and test it easier.

Customer: replied 1 year ago.
I can't get a pic of my xe90 trane right this Sec but I will. Is it the one with 2 wires on the outside and it sticks inside the furnace box about 2-3" and the interior wires are protected by whitish cloth like sleeves that seem to be a thermal protective barrier and its directly electrically connected to the roll out switch?
Customer: replied 1 year ago.
Here's what I think u r talking about....
Expert:  Daniel Plourde replied 1 year ago.

yes that is the high limit switch. did you check the voltage reading across those 2 terminals?

Customer: replied 1 year ago.
Customer: replied 1 year ago.
I've not yet checked. I will when I get home. Currently on the road, sorry
Expert:  Daniel Plourde replied 1 year ago.

ok next step is to check the volt reading across the 2 terminals of that switch. you should have 24 volts from one terminal to ground and 0 volts between the 2 terminals if the switch is good. to double check you can remove the wires and check the continuity too.

Customer: replied 1 year ago.
I understand
Expert:  Daniel Plourde replied 1 year ago.

let me know when you check that.

Customer: replied 1 year ago.
I will
Expert:  Daniel Plourde replied 1 year ago.

Ok

Customer: replied 1 year ago.
The voltage across the terminals was 0, but the voltage between the terminal(s) and ground was also 0. Then I noticed there was no voltage coming out of the circuit board. I think it's time to call a tech and have the circuit board replaced?
Expert:  Daniel Plourde replied 1 year ago.

there may be another limit switch located on the blower housing probally in the back.