Just this past weekend, I decided to turn on the furnace since it was cold to test out the heat before the winter. The fan starts but it doesn't blow any hot air, it just seems to blow air. This is our 2nd winter in this house with this furnace.

It's a Trane XV95 2 stage blower, the model number is UHCB080A9V3VA

I did have problems with it in the summer due to one of the pipes being clogged and water ran down along the side on the wires. I had an HVAC guy check it out and it was fine, he didn't see any damage. I have turned it off already and checked the filters as well.

I looked at this thread since it's a similiar furnace:

http://www.doityourself.com/forum/ga...r-problem.html

but for the life of me cannot find the flame sensor. There are too many white wires in there.

Thanks in advance.

 

Welcome to the forums.

That thread is not the same problem as yours. Your furnace is producing NO heat. The one in the link worked to heat and then stopped.

The flame sensor is not what you should be looking for.
If you have no flame.... the flame sensor has nothing to sense.

You should start by describing for us EXACTLY what happens.

Example....
Thermostat calls for heat
draft inducer starts
after xx seconds the igniter starts to glow
etc., etc.

 

Thank you PJ. I edited my profile and I am located in Toronto in Canada.

I am not too technical with the terms but I will try my best.

I turn the thermostat on and it calls for heat, I hear the fan working. I can't seem to find any location for the igniter. I do see the green light blinking along with a red light. The sequence is green blinks twice and red blinks four times. This only happens when the furnance fan is running.

When I checked my manual, the 4 blinking red lights indicates that it is a "Open Temperature Limit Switch" problem but I have no idea what that means.

I do have screen shots of the furnace with the covers doors off but unsure as to how to post them.

Thanks again, I hope that helps in any way.

 

Take the cover off the burner compartment of the furnace.

Carefully observe the SEQUENCE of events which occurs when you turn up the thermostat.

Report that sequence of events here, in order and in detail.

A furnace doesn't just "turn on." It follows a series of steps that ultimately result in heat. If a furnace isn't working properly, it is probably stopping at one of those steps. Pinpointing where that ignition sequence staops is often a key to identifying the problem.

 

Picture posting information.... http://www.doityourself.com/forum/el...-pictures.html

Please confirm the model number too.

 

Thanks, I am at work now but I am attaching the pictures:







The model number is TUHCB080A9V3VAB.

I will check the other stuff when I get home, I am assuming that I will have to have the doors off to look at this.

Thanks again for everyone's help.

 

Just quickly, can anyone tell from the photos where the pilot light is located? All the other 3 sides are solid metal doors that I would need to remove to take a look inside.

I will check the sequence when I get home.

 

There is no mpilot light. The furnace uses a hot surface ignitor, kind of an electric glow plug to light the gas.

The nHSI and the burners where the gas is burned are behind the viewing port visible near the top of the furnace inn the middle picture.

 

Thanks everyone for the help. I relented and called an HVAC technician since I wasn't comfortable messing around with my furnace anymore.

The problem was the flame rollover switch was burned out. He replaced it and now I have heat again.