Any furnace guys on here?

[MR.CJ-7]

I have a Carrier furnance (installed new with the home in '05). Occasionally the blower will be running but no heat coming from the vents. I look at the circuit board and the LED status light gives me error code 33. Which it tells me is a Limit Switch. Problem is I don't know WTF that is. From the manual that was left with the furnace I see there is a little switch thing above the gas burners. If I take it out, wipe it clean, power cycle the furnace it will usually start working. It happened a couple of times last year then again this morning. Today the filter was fairly dirty so I chalked it up to that.

On one hand I want to call a service tech to check it out, but on the other hand I know it is painfully simple and really don't want to kick out the coin if I don't need to.

Any advice?

 

[I Lean]

Team Fred on here might be able to help you out.

 

[spencurai]

do a google search. i had a similar problem and just got a new switch and it fixed the problem. jump the two wires that go into the switch and see if the furnace operates correctly.

what is probably happening is that the furnace thinks it is ooverheating so it shuts off the heat and runs the blower to cool down the furnace. it probably isnt overheating so get a new switch and see if that fixes it. it cost me less than 40 bucks for my switch and it fixed the problems.

 

[MR.CJ-7]

that is what I was thinking! I was mainly curious if the two wires were to be connected or open in a normal situation. I didn't want to end up frying the board.

Thanks I'll google the switch P/N and get one

 

[XT Utah]

do a google search. i had a similar problem and just got a new switch and it fixed the problem. jump the two wires that go into the switch and see if the furnace operates correctly.

what is probably happening is that the furnace thinks it is ooverheating so it shuts off the heat and runs the blower to cool down the furnace. it probably isnt overheating so get a new switch and see if that fixes it. it cost me less than 40 bucks for my switch and it fixed the problems.

Not a furnace guy here but I'd like to add that if this actually works you might want to spend some time making sure that the furnace isn't actually overheating. Cause, you know, an over heated heater has got to be pretty dang hot! (and dangerous)

 

[rholbrook]

Heres the skinny on it. This code can be triggered by 3 or 4 things. Two of these are caused if the wind is blowing hard enough to push air back down the flu. Was it blowing hard during the wee hours. If the fire is getting pushed back and causing heat to come out of the combustion area it will cause this error. If it wasn't windy it could be the safety switch going bad. A new switch is like $10. What I would do it shut off the power for a few seconds and then power it back up to reset the code. If it happens again then replace the safty switch. If it happens during wind, know that it is doing what it is supposed to do.

 

[MR.CJ-7]

I read that in the book about the wind and kind of ruled it out thinking it wasn't that windy, but then again I was asleep so who knows. Maybe my taking the switch out and cleaning it off isn't doing anything, rather maybe having the power switch off for a few minutes while I am R&R the switch is what is making it work agin