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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My trane xv90 is only blowing cold air. the red light is

Customer Question

my trane xv90 is only blowing cold air. the red light is blinking slowly and I cannot see the burner on
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

What is the pattern of the blinking? Is it just a constant slow blink or is there a pause like blink blink blink, pause?

Customer: replied 1 year ago.
constant slow blinking
Expert:  airheatman replied 1 year ago.

OK the slow blinking is usually normal but not receiving a call from thermostat.Can you do some hands on troubleshooting?

Expert:  airheatman replied 1 year ago.

We need to determine if issue is with furnace or thermostat first

Customer: replied 1 year ago.
sorry, it's actually three flashes, inducer error
Customer: replied 1 year ago.
we can do some hands on troubleshooting
Expert:  airheatman replied 1 year ago.

OK does the inducer vent motor actually come on?

Customer: replied 1 year ago.
i don't know what that meansthere is a noise that comes on when we press the button, it does sound like a motor. but i'm not sure if that is the "inducer vent motor"
Expert:  airheatman replied 1 year ago.

OK the inducer is the small vent motor where vent connects.It has to start and draw a vacuum on pressure switch to close it before anything else can happen.

These furnaces are what is known as a "condensing" furnace which means they actually condense water from the burning process and must be properly drained.

There are hoses in the furnace and a drain going outside.The slightest amount of debris or standing water in the main drain or one of those hoses will effect the vacuum on the switch.Also the slightest blockage in intake or exhaust will effect the vacuum.I have seen as minor as a spider wed in one of the vents cause this. Then add to that ,most of these pressure switches we get are imported from either China or Mexico and not unusual to get a bad one that sticks open or closed.

Expert:  airheatman replied 1 year ago.

If inducer is coming on. lets start by doing the following: I want you to locate the pressure switch. It will be a small round canister with a hose attaching it to the inducer housing. Remove hose from inducer housing and leave it attached to the pressure switch. Power off and back on to reset board again, Then call for heat at thermostat. Allow inducer to start then suck on the end of hose still attached to pressure switch and see if switch will close and burners ignite.

Customer: replied 1 year ago.
there is one round object and it is not small at all
Customer: replied 1 year ago.
that object has a motor and a duct attached
Expert:  airheatman replied 1 year ago.

Can you attach a photo of furnace with top panel removed?I will point it out

Customer: replied 1 year ago.
here is a picture
Customer: replied 1 year ago.
here is a picture of our entire unit
Expert:  airheatman replied 1 year ago.

These round silver canisters are the pressure switches. Locate the hose coming from inducer to do the above test.

Customer: replied 1 year ago.
although there are several hoses, none connect the inducer to the pressure switch
Customer: replied 1 year ago.
there is a long hose coming from what appears to be the burner to both parts of the pressure switch
Expert:  airheatman replied 1 year ago.

Can you see where it connects and remove to suck on hose with it still connected to switch?

Customer: replied 1 year ago.
i removed it and started it back on
Expert:  airheatman replied 1 year ago.

OK so did furnace come on when you did that?

Customer: replied 1 year ago.
nothing different happened
Expert:  airheatman replied 1 year ago.

OK if that did not help, check those hoses that go to drain and make sure no water is standing in them and main drain is not blocked.

Customer: replied 1 year ago.
was i supposed to suck on these hoses?
Expert:  airheatman replied 1 year ago.

Yes the one that came down from top

Customer: replied 1 year ago.
i did that, the motor got louder, the red light is now blinking slowly
Expert:  airheatman replied 1 year ago.

Is thermostat still calling for heat?

Customer: replied 1 year ago.
argh, i'm sorry again.
the blinking red light is still blinking red three times. the green light has turned off. the thermostat is on auto set at 70
Customer: replied 1 year ago.
should we continue to keep sucking on that hose
Expert:  airheatman replied 1 year ago.

Yes with call for heat continue sucking on hose and see if error code goes away.

Customer: replied 1 year ago.
no, the motor gets louder and faster but doesn't stop. THat same hose was attached to a small box that had a switch. I had originally detached both of them. I believe that box is for the gas. is gas leaking out now?
Customer: replied 1 year ago.
you can see the hose that comes from up top, and bifurcates into the switches and that other box
Expert:  airheatman replied 1 year ago.

I am about to leave office so I will open this to other experts.PLease wait to leave rating until someone is able to finish helping you with this.

Customer: replied 1 year ago.
how long will it take to find someone new?
Expert:  airheatman replied 1 year ago.

Depends on who is online today.Your problem is that the pressure switch is not closing.Could be blocked vent, water standing in one of those hoses or even an issue with heat exchanger, but will be a step by step process of checking each.