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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22672
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I own a Carrier 58MTA100-F-12116 Two Stage Furnace Serial

Customer Question

I own a Carrier 58MTA100-F-12116 Two Stage Furnace Serial 0205A13850. I've got at least two different diagnostic service signals, the latest one has been long-one short; one long-one short. Yesterday when I gave the furnace power the furnace blower came on and was running constantly; I opened the cabinet and read the diagnostic signal, after which, for some reason, the furnace cleared itself and the burner ignited and began operating. At the completion of the heating cycle the burner turned off but the blower continued to operate for at least an hour, after which time I cut the power to the furnace. Is this a limit switch problem coupled with a vacuum switch problem?
Submitted: 2 years ago.
Category: HVAC
Expert:  BillyHvac replied 2 years ago.
Is it safe to say you code is 11?
the code starts with short and then follows with long.
Thus 1 short, 1 long = 11
1 short one long = 21
Customer: replied 2 years ago.
My best guess is that the "latest" or most recent code is 11
Expert:  BillyHvac replied 2 years ago.


turn furnace off. Turn back on. code 12 should flash for 90 seconds. Then there should be a click and code change..or the unit will or the other. Try this and tell me code after the 90 second 12.

Customer: replied 2 years ago.
I will check the code again tonight. When I checked it yesterday I thought it was short long short long, etc.Now with what you have said, I'm thinking it could have been long short long short - as you say. At any rate there WAS a click after a short time and then the burner did ignite and the furnace did run but blower never shut off after room temp was reached. The blower just kept running. At that point I did check to see if there was a code and there was none, I had to cut the power in order to get it to shut down. The power is off now. If I give it power, the blower starts up but that is all - the blower will run continuously.
Expert:  BillyHvac replied 2 years ago.

Do the check out code wise.

The difference is if you turn power on to furnace while the thermostat is asking for heat or not. If it is it delays 90 seconds with the 12...then will go to regular operation