HVAC/Furnace help...no warm air coming out of vents..

[TriggerHappy]

Just replaced my thermostat thinking that was the problem. Unfortunately the fan still turns on, but no hot/warm air comes out of the vents. The reason I replaced the thermostat was because it wouldn't hold to a certain temp, figured that was the problem, guess not. I checked the breaker box, but nothing tripped (I had to turn off/on for thermostat replacement). I have forced air gas furnace. I have no clue. If I can't get this figured out on my own, I will contact Highclasswhitetrash to see if he can fix it for me, just trying to save some money. Any input is appreciated.

Its a Trane XL80

[hghclsswhitetrsh]

Make sure there is a call for heat, go downstairs and see if there are any diagnostic lights flashing. They will give a general idea where to start. Report back and I will try to help you here or text message. Don't reset the power switch until you get those codes.

[flogger]

Is it a set-back type thermostat? Many will have a fan on-fan auto switch. How old is the furnace? Is it a standing pilot ignition type? Make sure the access panels are on the furnace and no switches are being bypassed. The fan should not kick-in until chamber is hot. If it's a newer unit it has troubleshooting codes on the bottom panel. Good luck.

[Wulf202]

as above check for codes. it will have an LED that flashes for instance code 14 is 1 flash pause followed by 4 flashes.

[TriggerHappy]

Thanks guys, it is sending me a code, Im working with HCWT now. If I can't get it tonight, Ill get her fixed tomorrow. It sounds like a high limit switch.

[bryjcom]

Thanks guys, it is sending me a code, Im working with HCWT now. If I can't get it tonight, Ill get her fixed tomorrow. It sounds like a high limit switch.

Someone forgot to change their filter......

Or your blower is dead....

[TriggerHappy]

HCWT got me set up with a temp fix for tonight. Im all set until he gets here tomorrow.

[bellavite1]

Or your CPU board is dead...
Going through the same shit, been trying to troubleshoot all day.
Induced blower works, ignitor works, circulation blower works, gas valve was randomly working, today nothing happening there, cycling, ignitor glows but no gas igniting.
Going to look for a new board today...

[MarkCO]

High limits and sticky solenoids on gas valves are very common problems on today's furnaces.

The high limit usually goes bad because of lack of sufficient airflow (clogged or dirty filters) and then your furnace, for a time, cycles off the high limit which will burn it out in a few months.

[bellavite1]

Would the High Limit burn out gradually or die all at once?
My furnace was working erratically for the last couple of days and then this morning just died...
Are those high limits normally open or normally closed (as in can I jump the wires to test wheter that is the issue)?