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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 21761
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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We are having lukewarm air blowing out of the vents when set

Customer Question

We are having lukewarm air blowing out of the vents when set to heat. We have the thermostat set to auto, high efficiency Carrier furnace showing 3 short amber blinks, one long. Flame sensor lights up, burners come on. After 5 mins burners go out again. Can't figure out the problem.
Submitted: 9 months ago.
Category: HVAC
Expert:  Rick replied 9 months ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. First I’ll need some more info so I have a more complete picture of you situation.

A 13 error is a limit circuit open error. What do you mean when you say you "sealed the intake pipes"? also is the filter dirty? what do you do to restart the unit?

Customer: replied 9 months ago.
I'll try my best here until my husband is home. A few years ago kids put rocks in the pvc pipe outside that leads inside to our basement. We had them removed and no other issues. Where the tech cut to get rocks out the pipe was dripping water condensation. My husband replaced the section of pvc and re-sealed it. He powered the switch off on the furnace unit and cleaned filters.
Customer: replied 9 months ago.
He thought the problem was a bad pipe reducing suction.
Expert:  Rick replied 9 months ago.

Ok just wanted to e sure you weren't blocking any vents in the house because that could cause the heat exchanger to over heat which would give this error. A dirty filter can also cause this error. Is the unit still not working right? did you try turning the power off to it then back on a minute or so later?

Customer: replied 9 months ago.
Okay. Come to think of it a siding contractor told us we were losing child air to the outside through an intake vent in a bedroom when the air conditioning was running. He advised us to cover the vent with plastic. Furnace still not functioning correctly.
Customer: replied 9 months ago.
Sorry cold air
Expert:  Rick replied 9 months ago.

It's possible that covering that vent could cause the unit to overheat. I'm not clear on how it could be losing air to the outside but you might try uncovering it and then cycle the power off then back on like I mentioned before. Beyond that you can try resetting the rollout switch(es) (see attached pic for typical). They are located just outside the burner chamber. Turn off the power then press the small button between the 2 leads to reset it. If it clicks you have reset it and the unit will fire up when you turn the power back on with any luck. If it doesn't click it wasn't tripped.

Check to be sure there isn't more than one by tracing the leads connected to the switch.

Customer: replied 9 months ago.
I'm powering off now and will restart to see...
Expert:  Rick replied 9 months ago.


Customer: replied 9 months ago.
No luck, husband said it gives error code 31 not 13. He tried resetting previously, he said it did not click, wasn't tripped.
Expert:  Rick replied 9 months ago.

First digit = short flashes second digit = long flashes. A 31 error is entirely different. It's a draft pressure (switch) error. The question is do you have a bad switch or a weak fan or a blocked exhaust vent. You can check the vent for blockages and also the vac tubing connected to the switch. Be sure the tubing is not kinked, deteriorated or doesn't have water in it. You can also poke a paper clip into the port where the tubing connects but not into the switch connection. If all that checks out. Turn the power off to the unit wait a couple minutes then turn it back on. After the fan starts remove one of the leads from the pressure switch and connect it to the other lead. If the sequence continues then you may have a faulty pressure switch or possibly a weak fan. The next thing we would do is put a manometer on the exhaust to check the actual draft pressure but you aren't likely to have a manometer and they are expensive. Replacing the switch is one other option since it's less money than a manometer (or a new draft fan) and it is a likely culprit.