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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22006
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have A trane xb80 the ac stopped working.. Digital thermostat

Customer Question

I have A trane xb80 the ac stopped working.. Digital thermostat is set right. Was working yesterday.. Took off furnace cover red light just keeps blinking.
JA: Thanks. Can you give me any more details about your issue?
Customer: The furnace blower will not cycle on when thermostat calls for ac
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Submitted: 6 months ago.
Category: HVAC
Expert:  BillyHvac replied 6 months ago.
hello, is the light in furnace blinking a slow pattern or a certain 3...3...3..or is it just steady?
Customer: replied 6 months ago.
Just steady
Customer: replied 6 months ago.
Are you still there
Expert:  BillyHvac replied 6 months ago.
ok remove top section of thermostat...take R wire and G wire and touch together...does blower kick on?
Customer: replied 6 months ago.
Will try
Expert:  BillyHvac replied 6 months ago.
standing by
Customer: replied 6 months ago.
No blower did not start
Expert:  BillyHvac replied 6 months ago.
ok you have something like a water drain switch, full pump switc, wet switch etc stopping power to the thermostat...can you tell me where the unit (ac) drains to inside?
Customer: replied 6 months ago.
Yes I can see the pvc drains should I disconnect
Expert:  BillyHvac replied 6 months ago.
we are looking for 2 wires that would go to the drain or furnace in basement or attic?
Customer: replied 6 months ago.
Attic.. Long line set... I just see where the pvc drains from coil... I don't see any wires
Customer: replied 6 months ago.
But even if I try to turn on heat that will not work either
Expert:  BillyHvac replied 6 months ago.
ok if in attic you have a safety pan switch or drain switch as it is required by code...this protects against water damage by turning ac off if plugged. You will need to use a shop vacuum and suck all the pipes out or safety pan...once the drain is clear the unit will come back on. Billy
Expert:  BillyHvac replied 6 months ago.
heat will not work either because the water switch has cut power to the thermostat
Customer: replied 6 months ago.
I see the pan the furnace sits in no water at all in pan
Expert:  BillyHvac replied 6 months ago.
you may not even see water....but drain is backed is summary The steady blink tells us the system is ok and "waiting"By putting red (hot) to green should force the blower on...since it does not we know we dont have power at thermostat. That means somewhere from the R terminal in the R terminal in thermostat..there is an open switch or connection..
Customer: replied 6 months ago.
Where else might I find this water sensor.. And could the sensor be bad.. Meaning there is no water but it thinks there is
Expert:  BillyHvac replied 6 months ago.
if you open the will see thermostat wires on same terminals as thermostat. Tis is where they start to then run to thermostat. The R terminal is what we are concerned with....follow the wire that attaches to R in the furnace...see if that wire goes to ANYTHING other than straight to thermostat...odds are you follow it to a switch that is open...unless you have a bad wire..
Customer: replied 6 months ago.
I traced it all the way thru the wall. The res from the thermostat screws to a terminal on the inside of the furnace.. T
But no other wire from there. To a switch.
Expert:  Gaztech replied 6 months ago.
I noticed Billy has not responded back to you,I will assist you with the the furnace terminal can you put a jumper between R and G to see if blower starts.And if possible take a voltage reading between terminal R and C you should read <=24 V ac.
Expert:  BillyHvac replied 6 months ago.
When you say red attaches to a terminal inside the it the R terminal on the circuit board? Billy