I have a Trane XR80 furnace that has an LED flashing 4 times--Open High Limit Device. The filters are new and clean, I replaced the high limit switch, cleaned the flame sensor. Are there other switches I could check? Any other ideas?

Thanks for any help or ideas.

Brian

Are you sure the high limit you replaced is a good one?

Usually after you replace the limit and turn the power back on the code will clear.

Are you sure the high limit you replaced is a good one?

Usually after you replace the limit and turn the power back on the code will clear.


Thanks for the quick reply. How would I test the new limit switch? Also is this the only switch that could be a problem?

It depends upon the drawing but usually they are closed which means power will flow thru it. When activated/defective it will be open and no power will flow thru it.

It depends upon the drawing but usually they are closed which means power will flow thru it. When activated/defective it will be open and no power will flow thru it.

Well I tested the limit switch and the two manual reset flame rollout switches that are inline with the limit switch. All seem to work correctly. When I turn to power back on, the system will work for about 1 min, then quit with the open high limit device code. If I recycle the power it will again work for only a short amount of time... The only switch I can't get to is the reverse flow switch. I don't think that switch is the problem? I am starting to feel it may be the integrated furnace control?? Any more ideas? Thanks agian

Well I tested the limit switch and the two manual reset flame rollout switches that are inline with the limit switch. All seem to work correctly. When I turn to power back on, the system will work for about 1 min, then quit with the open high limit device code. If I recycle the power it will again work for only a short amount of time... The only switch I can't get to is the reverse flow switch. I don't think that switch is the problem? I am starting to feel it may be the integrated furnace control?? Any more ideas? Thanks agian


Your limit switch is a safety device for your furnace . It works by monitoring the operation of your furnace and if it's limit is exceeded then it opens or closes to tell the control board that it's limit has been exceeded . Most common limit problem is usually your "High Limit Switch" which monitors the temperature around your heat exchanger if it is exceeded usually more than 180 deg F it will open up causing a fault to show up on your control board . This does not mean that the limit is defective but rather that something else has caused the temperature limit to be exceeded ,most common being poor air flow through the furnace usually dirty air filter, blower or even a defective blower motor . Check and make sure you do not have any other problem that could be causing this situation.

Your limit switch is a safety device for your furnace . It works by monitoring the operation of your furnace and if it's limit is exceeded then it opens or closes to tell the control board that it's limit has been exceeded . Most common limit problem is usually your "High Limit Switch" which monitors the temperature around your heat exchanger if it is exceeded usually more than 180 deg F it will open up causing a fault to show up on your control board . This does not mean that the limit is defective but rather that something else has caused the temperature limit to be exceeded ,most common being poor air flow through the furnace usually dirty air filter, blower or even a defective blower motor . Check and make sure you do not have any other problem that could be causing this situation.

Your response to this question is very helpful. I've got the same diagnostic and your explanation makes sense.

I have a Trane furnance and am having problems with it the pilot light won't stay lite. The led will flash continously then the pilot goes out, then turn it back on and flashes three times and goes out, turn it back on and then flashes four times. What's my problem?? Without heat it is Friday night 9:36 p.m. how can I fix this problem in the morning??

Find the service label with the LED diagnostic codes-usually on the control board housing or inside the blower/service access panel. Post results of your findings.

Did you ever figure out what the problem was? I am having the same problem and the limit switches are OK?

Hi, same issue here Trane XR80 4 flashing light.

my thermostat signals the system and the motor starts blowing air, then the light starts doing the 4 flashes while to fan blows non-stop, not realizing that the burner hasn't ignited.

the gas lines are turned on and other applicances working.

just stopped all of a suddent one day as i was only getting cold air.

i've try powering down the furance and the same thing happens when i turn it back on.

what can i do? i don't see the limit switch, all i see is the circuit board while looks fine.

So the limit switch was the issue.
the tech came in and fixed this for me.

all you have to do is follow your circuit chart to find the limit switch, mine was screwed in flush to the metal vents.

take that out, check power reading first (if you suspect it's dead), otherwise, smack it around a few times and it should reset.

my issue was due to dirty filters.

screw it back in place and you're burner should fire up now.