Ask Experts Questions for FREE Help !
Ask
    Wester's Avatar
    Wester Posts: 3, Reputation: 1
    New Member
    		  
    #1

    Jan 17, 2008, 09:00 AM
    Furnace is shutting off early and still blowing cool air.
    Hello,

    I have a Trane XE80 (14 years old) that periodically shuts the gas off but the blower continues to blow trying to heat the house up. If I shut the furnace off, allow it to restart, everything will work fine for a few hours or days. So the occurrence is random.

    Some background info. About a month ago we had a "shyster" repair tech come and diagnose our furnace for what appeared to be a bad blower fan motor. He said it was bad and that the heat exchanger was cracked, but told us if he fixed it ($1193.00 motor only) we should be OK for while. I got rid of him, and got another tech. It ended up only being a bad capacitor ($12.00), however the motor was squeaky and we determined that the motor shaft was getting loose. We replaced it also ($170.00). So, I am concerned if the first repair tech sabotaged the furnace.

    My only other thought is the temperature sensor in the flew area is getting to hot and is shutting the gas off, but I should see the gas turn back on once it cools down and the furnace doesn't appear to be doing this.

    Any thoughts?

    Thanks!
    therinnaiguy's Avatar
    therinnaiguy Posts: 153, Reputation: 5
    Junior Member
    		  
    #2

    Jan 17, 2008, 01:45 PM
    When the furnace shuts down, look for a diagnostic light on the control board. Do not open the cabinet up to look for it, it will be seen through a small viewing port in the lower section. Count the number of blinks and record. Now remove the door panel and on the sticker found on the back, there will be a diagnostic chart. Let us know what you get for blinks.
    Wester's Avatar
    Wester Posts: 3, Reputation: 1
    New Member
    		  
    #3

    Jan 17, 2008, 03:04 PM
    Further diagnoses: OK I have removed the Thermostat from the equation and direclty hot wired the R (red) W (white) contacts/wire. So I now know the Thermostat is not turning the gas off. So the furnace is in permanent on mode. Basically the furnace is on for about 5 minutes, gas shuts off for 2 minutes then back on. It keeps repeating this cycle.

    Also, when the gas shuts off (which appears the furnace mey be getting to hot) I get a 4 blinking light pattern which = Thermal Protection Device is open. Otherwise it is in a constant blinking mode which = Normal Operation pulling heat.

    I am only guessing but what do think of it being the bi-metal (hi-lo) switch?
    therinnaiguy's Avatar
    therinnaiguy Posts: 153, Reputation: 5
    Junior Member
    		  
    #4

    Jan 18, 2008, 06:52 AM
    Is the room air blower turning on? Have you checked your air filter? How hot is the supply plenum getting (super hot, warm to the touch)? Are all registers open and unrestricted?

    Sorry to ask so many questions but there is a reason.
    Wester's Avatar
    Wester Posts: 3, Reputation: 1
    New Member
    		  
    #5

    Jan 18, 2008, 08:56 AM
    After more diagnosing, I removed the Fan/Limit Temperature Switch from the equation, by hot wiring the to wires together. The furnace ran perfectly. I conitnued testing the switch with a Ohm meter and could see that the switch was opening up after five minutes of operation.

    This helped me out.

    Furnace is shutting off early and still blowing cool air.? - Yahoo! Answers
Not your question? Ask your question View similar questions
 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Furnace barely blowing cool air [ 4 Answers ]

Hi,I have a concord 80 plus furnace installed in 2002... Everything is kicking on the fan turns on, the igniter ignites the gas , and a minute or so later the blower comes on... problem is the air is cool and barely blowing?? all vents are open correctly... cold air return is working fine... filter...

Furnace blowing cool air [ 3 Answers ]

I have a Bryant gas furnace. About 2 days ago it was working fine. Yesterday I noticed it was very cool in my house. I checked the vents and they were blowing cool air. The fan stays on continuously. The pilot is lit and the filter is new. What are some possible causes and solutions to this...

AC blowing cool air but not cold? [ 3 Answers ]

All of a sudden my AC is blowing cold air. Actually it is cool, but not like it should be. I am a new home owner, not a handy man. What's the problem, please help.

A/c not blowing cool air [ 1 Answers ]

My a/c ceiling unit is set at 78 degrees but it stopped blowing cold air,I did turn it off for 2 hours and turned back on and started blowing cold air for just over 24 hours. But is now just blowing warm air.

AC not blowing enough cool air PLEASE HELP! [ 16 Answers ]

:confused: Just my luck that out AC goes out on a holiday! We live in Texas so it is normally pretty hot and humid but recently it hasn't been. To get to my problem our AC is not pushing out hardly any cold air from the vents. We live in a 2 story home with a thermastat upstairs and down. We were...

View more questions Search