HVAC Questions? Ask an HVAC Expert for Answers ASAP
Thanks for giving me the opportunity to help! Could this be a thermostat issue? What does the three flash code stand for? There should be a code legend inside the furnace somewhere.
I don't know what the 3 flash code is. I took the cover off the furnace and didn't see any code legend. I'll look again.
I believe the thermostat is working as it should
Yes, there should be one inside the lower door of the furnace. It may also be in the manual if you have it.
OK, I think it says "pressure switch fault"
OK, that helps. So blower starts ramping up and then furnace shuts off?
I don't have the manual
Try this. On the pressure switch there is a hose coming off it. Take the end off not attached to the pressure switch and suck and blow in and out a few times, then replace.
What does the pressure switch look like?
Do it gently
ok, I'll go look for that
is it possible there are two of them?
the black rubber hoses coming off of both of them are connected with a T, and that goes up to what I think is the main gas valve. Sound right?
Yes, must be a 2 stage. Suck and blow them individually.
Be gentle about it as there's a diaphragm inside
I did that, and I could hear each of them toggling when I did. Replaced the covers and it's still doing the same thing. I was gentle :)
Then most likely you have a bad pressure switch.
Now I'm basing that on the code you gave me and what it said on your furnace, remember, so make sure that's accurate.
Yes, I think that is accurate. The code legend clearly says pressure switch fault, and it is definitely flashing the red LED 3 times
OK, then most likely the lo fire pressure switch is defective.
so is a pressure switch failure common?
It's not common, but can happen
the furnace appears to be about 5-6 years old
Yes, I've seen it happen, though. Try this: take one of the two leads off the pressure switch (one at a time) and see if furnace tries to start
I'm talking about the wiring leads
Don't worry about getting a shock--it's low voltage
I'll stand by
I took one lead off of both switches at the same time and it did the same thing. I took one lead off of the top switch and it did the same thing. I'll try taking one lead off of the bottom switch
same thing happened
That's interesting. Well this may be more complicated then just a pressure switch. It may be a problem with the board. Normally switches should be open and as inducer comes up to speed they close. That's why I had you take one lead off-in case they were stuck closed. At this point, you may have to get an HVAC person involved as it gets more complicated trying to determine if it's the board or the switches.
I'm not one for replacing parts if they aren't bad.
ok, we have a relative that is in hvac, so we'll call him. I have to take the kids to school now...thanks for your help. I'll leave the chat open, so if you want to hang on, I'll be back in about 15 minutes
I'm going to switch to Q and A mode, however but you can still post responses.
My local HVAC guy helped me figure out it was the air intake pipe was clogged with snow outside. Thanks for your help. -Greg