Furnace overheating, overlimit switch opening, have replaced blower motor and capacitor, control board, and filters. Have cleaned all air supply boxes and ducting. Also cleaned evap coil. All vents are open and clean. Checked overlimit switch for proper temp. range, open@ 170F closed@ 130F. No flame rollout. Will run aprox. 2min then overlimit switch opens and gas shuts off. Will run fine if I remove blower motor door. Sets code 33. Any other ideas? Please help!
If it works with blower door off sounds like it's not getting enough return. What's the statics? Try an adjustable limit, I think they go to 210. Good Luck!!
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SOURCE: Pressure, draft safeguard, or aux limit swtch did not close or re
The limit switch on the inducer has tripped. There are two wires that go to a small disk about the size of dime that has a small button in the center. Push this little button and you will feel a littl snap and the unit should fire up. Check all the manual reset limits as well. If the unit still won't start, jump the two wires by bypassing the limit switch. If it starts, then replace the switch. Bypassing the switch is only temporary and could lead to death if it is used as a permenant fix.
SOURCE: Carrier weathermaker sx 58 furnace
I have serviced these furnaces for 20 years and I can tell you most of these models did not have diagnostic lite on them. (although some did, especially if the control board has been replaced) The problem is most likely a bad 3 wire pilot. This will cause exactly what you describe. 2 things to consider though. 1, If you were to replace the pilot don't get a cheaper knockoff. In my experience these do not last long at all. Get the right one from a carrier dealer. It will cost more but be much more reliable. 2 What is the condition of the secondary heat exchanger? Most if not all of the sx series had issues with the secondary heat exchangers rotting out and leaking. If the furnace is out of warranty you would be much better replacing the furnace as the cost of replacing the secondary heat exchanger will probably be almost the same as a new furnace. ( those babies are EXPENSIVE!)
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