I have an Aire-Flo Furnace ( Model AF90MPE075U3). Last winter it began malfunctioning. The local repair man said the inducer fan was bad and replaced it. It worked for a while and began acting up again. He then decided the intake air line was to small and not sloped properly. I added a second line and resloped them both. It didn't help. All of this was around $400. It then warmed up. This year it started working fine. Then it began to malfunction again. I called a second service company. They came out twice. They said it was the exhasut line not being sloped properly, I changed it, no help. Then they said it was the drain line to the condensate tank not being properly sloped, changed it, no help. This was about $250. Please note the furnace is about six years old and has worked perfectly until now. The third company came out and trouble shot the furnace, he said he would have to replace the gas valve ($780 + labor) before he could properly trouble shoot the furnace. $168 for his time. I took some time to think about it. A couple of days later I turned the power back on to the furnace and it worked fine for one night. At this point nothing happens at all, the inducer fan will not start the ignition process. The LED on the gas valve (Honeywell SV9520H8042) gives a code which says the pressure switch is closed and should be open. For information I checked the Roll Out Switch, it measured 25 volts top and bottom. The Pressure Switch measured 21v at the top and 25v at the bottom. The Pressure Switch Vent runs to the condensate collection tank. I both blew and sucked on the line and could hear the switch click each way. This did not change the code the LED was flashing. As I am tired of paying for bad information and unneeded parts any help would be appreciated. Thank you, Jeff Turner

Man, I feel your pain. You better do some research to find a good service company. That's what you need most.

It could be the gas valve, but there is a bunch of stuff I would check first. If I would type out my whole troubleshooting routine I'd be at this keyboard WAAAAY to long. Suffice to say that if you can't figure out what that error code means by reading the schematic and doing some judicious testing, you'd be better off spending your time on service provider research. If you mess up a gas-fired system yourself, your homeowners insurance may not cover the resulting property damages, not to mention your lives.