pressure switch issues

[burninlifeaway]

I've been working on a tappen gas furnace. The Inducer motor kicks on and runs for about 30 seconds and I couldnt get the furnace to fire. After removing the rubber tube and clearing out a small piece of debris I went ahead and made sure the points the tube hook up to are also clear (good old paper clip trick). after wards the furnace fired and worked well for a few days I recently got called back for the same problem except this time the ignitor lit and the circuit bored flashed a code of three blinks ( pressure switch stuck closed ). After i recieved that code it went back to the motor running for 30 seconds and then stopping. Any ideas on what it may be if its not the pressure switch??

[bullmoose]

Did you check pressure on draft motor? Amps on draft motor? Capacitor?

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[dugfish]

Did you pull the inducer and look at the choke disc.

[jrbenny]

http://www.trutechtools.com/Testo-51...ter_p_586.html

http://www.trutechtools.com/TruTech-...it-_p_630.html

You need to measure what the pressure switch is sensing and go from there.

[Joehvac25]

I hate when people ask questions then never return.

[jmsmars1]

pressure switch stuck closed? do you mean open contacts? did you remove the wires from the pressure switch and check the contacts with an ohmmeter to verify? is there anything else in the pressure switch circuit (like a high limit switch)? verify 24v to the pressure switch?

[burninlifeaway]

The motor seems to be working properly and the 24v circuit seems to be okay I'm still a fairly new tech. so I don't quite have all of my tools yet but, the motor is creating enough suction to hold a piece of paper steadily at the end of the hose. The code i recieved was pressure switch stuck closed 2 flashes would have been stuck open. Sorry it took so long for me to get back with y'all I have been having some internet issues

[canusayinsanity]

I've ran into this situation once before. A - it could be a bad pressure switch. or b- some how condensate is getting into pressure switch shorting it out so at all times moisture is acting like a conduit for 24v front one contact to the other. Make sure condensate drain isn't plugged.

[burninlifeaway]

that has actually been a worry i had i havent been able to get back to over to the unit yet but i noticed the last time i was there a small drop of water coming from the vent pipe that dripped down into the unit it self. I know it was only one drop but if it happend one time i was sure itd happen again so blocked i used silver tape and a scrap of sheet metal i had to block the water from falling into the unit for the mean time but havent checked the drain yet thanks!!

[canusayinsanity]

If its 90% furnace then what I've said applies. If its 80% then rain cap may be gone allowing rain water/snow and such to flow down flue and into inducer housing where wheel will sling water into tube of pressure switch as well. Just suggestions of what to look for.

[burninlifeaway]

just an update on the situaition (( note its a friend of mines furnace he has two other sources of heat hes been using for the past 2 years a gas wall heater and an electric fireplace )) i finally purchased a manometer and found the inducer motor is pulling 1.25 inches of water column which is more then enough to activate the pressure switch. I did find the rain cap is bent on one side pretty badly. the furnace ran fine for a night after i replaced the inline fuse. That morning he turned down the temp on the tstat and it started doing the same thing AGAIN. Inducer kicks on runs for 30 seconds and kicks off. It almost seems like everytime im there running tests and trying to figure this out for an hour or two it will eventually kick on and start working but the next day its back to the same thing. i check all the safetys in the 24v circuit all of them are working the inducer is getting proper voltage. im running out of ideas

[burninlifeaway]

oh and i forgot to mention it is a tappan 80% gas furnace model g6rk072c-12

[gravity]

check the resistance thru all your safeties. pull the 2 wires of the pressure switch, turn on inducer, and check resistance thru switch. if you read more then 1-2 ohms replace the switch. pull the flue off and check for a squirrel or a bird in it.