Have HVAC Questions? Ask an HVAC Expert for Answers
Hi, I'm Tim, an HVAC expert here to help you resolve your issue. Please provide as much information as you can. Also, I may depend on you to be my "eyes and ears" since I'm not there onsite. At the end of our dialog, when you're satisfied with the answer, you will have a chance to rate my service. Please wait until then. I'm sorry to hear about your issues with your furnace. It sounds like either a bad gas valve or a bad board assuming we have good gas pressure to the furnace. What flash code do you get? Also full model number will help.
Have you checked intake and exhaust pipes for blockage? If not, that will be the first step.
Sometimes doesn't take much. Even a leaf getting sucked into the intake pipe can cause an issue.
Take the intake pipe off the top of the furnace, Usually this is not glued in place.
Does it work OK now without the pressure switch code?
Next thing check the pressure switch and pressure switch hoses? Hoses kinked, disconnected? May want to try blowing them out.
Check the barbs on the hose end opposite the pressure switch. Barbs clear?? May want to ream them out with a small drill bit.
The pressure switch hoses attach to a "barb" both on the pressure switch itself and the other end may go to the inducer motor or collector box. I'd like you to take hose off, check those barbs. I'm not worried about the barbs on the pressure switch itself, just other end.
If these check out and inducer motor is running, check the condensate drainage system. Take hoses off, blow through them, check "trap" down in the blower area. Sometimes this will plug up not allowing condensate to drain properly.
Check for voltage to the gas valve when that happens. Get a meter, set to volts AC and check at the top posts of the gas valve for voltage. If the gas is off, but valve has voltage, we may have a bad gas valve.
You need to check all the things I mentioned. If everything checks out and you have the pressure switch code, it may just be a bad pressure switch. I will be tied up until the afternoon on a heat exchanger install, but can always respond back later when I get back. The chat will remain open.
Were you able to find a voltmeter so we can continue?