Gas and Oil Home Heating Furnaces - blowing cold air

I have a Trane TDE060A936K2 Forced air furnace about 8 yrs old. it started blowing cold air. I checked the status switch and 4 flashes indicated an open high limit. How can I fix it? Please help.

Thank you,

Cuong

First thing to try is turning off the power at the switch or breaker. Leave it off for about 30 seconds & turn back on. If furnace lights then goes off again on limit, check for a dirty air filter or blocked return vent.

If this furnace blows down (blower in top part of the cabinet) check for a manual rest button (usually red).

And if after trying the steps Grady recommends things still look bleak, I had an identical problem about a month ago, also with a Trane furnace.

I ran continuitiy tests on all the safeties and they were all good; then jumped limits and flame rollouts to no avail. The LED was flashing as to indicate an open limit failure and the blower was blowing cold air. But the limits and safeties were all good. I replaced the module and the furnace went back to its normal well behaved operation.

I ran continuitiy tests on all the safeties and they were all good; then jumped limits and flame rollouts to no avail. The LED was flashing as to indicate an open limit failure and the blower was blowing cold air. But the limits and safeties were all good. I replaced the module and the furnace went back to its normal well behaved operation.

Can you explain the above? I've got a 3-year-old Trance XR90 that is just blowing cold air. I discovered today that the ignition won't light. There is a blinking red LED on the Intell-Ignition circuit board. Does that indicate something wrong?

How do you do the continuity tests?

And when you say "replaced the module" which module are you talking about? Where can a person order such a thing?

Thanks for any help. This is highly frustrating as this furnace which I had put in just 3 years ago has gotten very little use. I'm refurbing the house and nobody has been living there for the past 4 years. The heat has been only set to maintain non-freezing status most of the time, with higher temps only on the days I get to work on the refurb project. How can something so little used just stop working?

One of the things I do not like about those LED flash codes is the codes are often too vague. They might say something about the limit is at fault, yet the limit switch may be good and it something else affecting that, as one example. Another example I have is on this one smart valve it flashed the code saying the pressure switch was faulty. It wasn't; it was the smart valve itself that needed replacing. The flashing code did not even come up that the smart valve was bad, even though that was listed as a flash code!

Do you know that if you run a furnace in a cold house, that with some units, with a fan temp switch, the furnace will run for a short, but then stop blowing because the cold return air cools the heat exchanger too much?, and it will cause the blower fan to short cycle for the longest time until the house finally warms up enough? Cold houses can also cause soldered connections and spade connections to shrink and lose contact when things are marginal.

We need to know the sequential steps your furnace is doing or also not doing. I made a post maybe an hour ago in another thread that asked a poster a lot of relevant questions and it be good if you could read that post I made and tell us what your furnace has (regarding my questions) and what your furnace does and does not do.

That thread is called "Furnace stops working when..."

One of the things I do not like about those LED flash codes is the codes are often too vague. They might say something about the limit is at fault, yet the limit switch may be good and it something else affecting that, as one example. Another example I have is on this one smart valve it flashed the code saying the pressure switch was faulty. It wasn't; it was the smart valve itself that needed replacing. The flashing code did not even come up that the smart valve was bad, even though that was listed as a flash code!

Do you know that if you run a furnace in a cold house, that with some units, with a fan temp switch, the furnace will run for a short, but then stop blowing because the cold return air cools the heat exchanger too much?, and it will cause the blower fan to short cycle for the longest time until the house finally warms up enough? Cold houses can also cause soldered connections and spade connections to shrink and lose contact when things are marginal.

We need to know the sequential steps your furnace is doing or also not doing. I made a post maybe an hour ago in another thread that asked a poster a lot of relevant questions and it be good if you could read that post I made and tell us what your furnace has (regarding my questions) and what your furnace does and does not do.

That thread is called "Furnace stops working when..."



Hello ecaman,


I agree that explantions for error codes are frequently poor.

Just as you describe, they often require a skilled repairman who can imagine the range of possible problems that may be at issue if a limit switch shows as being opened. That's obviously 'way different than simply choosing to replace a limit switch.


Oh well. better than having no record at all of what might be happening, especially with intermittent problems.