any furnace guys around?

I had an issue with my furnace tonight where it wouldn’t go on. it is a Carrier 58MXA. I could see the little red light was flashing a code. I looked up the code and it indicated it was a pressure switch fault. Tried resetting the furnace to no avail. Did some googling and most common trouble shooting suggestion was to disconnect the fresh air intake and see if that corrects the problem. If it does, there is most likely a blockage in the pipe.

Did as suggested and sure enough, furnace fired up after resetting. I could only get the pipe about 2 inches away from where it connects but that was enough to allow more air in. How does one determine if there is a blockage in a pipe that is about 40 feet long with 3 corners in it? Do I have to cut the PVC apart? Could it be something other than something in the pipe? Not sure what could get in there as it is 10 feet up the side of the house where it comes out. Any suggestions?

if you have a way to blow a large volum of air through it blow it out , I had a lady’s kids who threw rocks in the pipe and the furnace wouldn’t run, once the rocks were gone she was good to go.
Stan

Get the ladder out and check the opening first. Screen may be plugged with something you can get yourself. Otherwise find a plumber with a snake camera and look inside the pipe.

Have you tried a shop vac, 2 1/2″ hose is same as OD on the 2″ PVC pipe?

I can’t get the pipe far enough out of the furnace to get a hose on the end to blow it out. That was my initial thought. Will see if I can figure out a way to get the pipe out further.

Could you snake a downrigger cable through it and try to pull a rag through?

Mine wouldn’t fire up last year and I had a condensation drain plugged up. Couldn’t figure out how enough crap got in there to plug it up but it did.

What about vaccing it out from the outside, it will be the one turned down? Also, if you don’t have an atmospheric vent water heater right next to it or in a small enclosed room, you can run with taking combustion air from inside the room. You need 50 cubic feet per 1000k BTU’s. It would have the venting instructions in the manual for what I’m talking about, at least to get you through the night with heat.

Leaf blower John.

Works on our dryer vent every year.

Inside the furnace there should be a plastic condensate trap. It would connect to the train line from the furnace. Make sure that is not plugged. I have seen them get plugged with dust and it will build up into almost mud.

If that’s clear check the exhaust and intake pipe.

had similar problem and all that was wrong was a sag in the exhaust vent about a 1/4 of inch-which allowed moisture to gather–good luck

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Inside the furnace there should be a plastic condensate trap. It would connect to the train line from the furnace. Make sure that is not plugged. I have seen them get plugged with dust and it will build up into almost mud.

If that’s clear check the exhaust and intake pipe.

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I found the condensate trap. Pulled the drain connection off and no water came out. Pulled the bigger hose going into it and about a gallon of water came blasting out. Guessing that trap is plugged. Can they be cleaned our or do I need to get a new one?

I just had to replace a faulty pressure switch on my Tappan furnace last night. I would check the switches while you are at it. Simple continuity check with a meter. Mine are vacuum/pressure switches so putting a meter on the electrical contacts and disconnect the vacuum line and should get contact while sucking and blowing on the line. Mine was a faulty low fire switch what would make contact about 50% of the time.

Symptom was thermostat would call for heat, inducer motor would ramp up to high for about 15 seconds to get air moving then slow down, igniter would turn on and glow but gas valve would not open. Then it would shut down and go into fault.

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Inside the furnace there should be a plastic condensate trap. It would connect to the train line from the furnace. Make sure that is not plugged. I have seen them get plugged with dust and it will build up into almost mud.

If that’s clear check the exhaust and intake pipe.

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I found the condensate trap. Pulled the drain connection off and no water came out. Pulled the bigger hose going into it and about a gallon of water came blasting out. Guessing that trap is plugged. Can they be cleaned our or do I need to get a new one?

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Clear your drain lines with a shop vac

Remove it and run water from the faucet through it. Fill it an shake it up a little to loosen the debris and flush again until its clean.

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Remove it and run water from the faucet through it. Fill it an shake it up a little to loosen the debris and flush again until its clean.

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Flushed it multiple times with hot water. Lots of crap came out. Kept flushing until nothing more came out and seemed to be flowing through. Put it all back together, turned it on, and worked like it should. Thanks for all the suggestions and help. Saved me a couple hundred bucks for sure and I learned something new.

I had one over the weekend with the same problem after fixing the drain line the furnace ran BUT quit on high fire. Carrier on their great wisdom hooked the pressure switch to a nipple at the bottom of the heat exchanger and the plugged condensate pushed water into the pressure switch. It worked on low fire but high it would fail. I got about 1/2 Dixie cup of water out.