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mpinoly · Dec 25, 2008, 09:45 AM

My Trane furnace is not putting out heat. Thermostat works, fan blows but burners are not lighting. Getting 3-flash error code, which, according to the manual is a Draft Pressure Error - possible problems, venting, pressure switch or inducer.

I've turned off power, turned on. I've turned off gas, turned back on. Vents are clear - is there anything I can do to reset this and get it to light the burners again?

KC13 · Dec 25, 2008, 09:51 AM

Try tapping on the pressure switch - it may be sticking in the wrong position. Does the inducer run? If not, the switch won't engage - or the switch is stuck in the closed position. If inducer does run, switch is not closing as it should - could be a blocked flue or a bad pressure switch.

mpinoly · Dec 25, 2008, 02:42 PM

I don't know what or where the inducer is.

KC13 · Dec 25, 2008, 03:10 PM

It is the vent motor connected to the flue.

mpinoly · Dec 25, 2008, 04:02 PM

Thank you. The vent motor does run and air is flowing. If I set the thermostat high enough that there is a "heat request", the fan business clicks on and runs but there is no "clicking" to ignite the burners and of course, the burners are not lighting.

Must be a bad switch?

mygirlsdad77 · Dec 25, 2008, 05:38 PM

Check hose that goes from pressure switch to draft inducer. Make sure it is not rotted or cracked(must be airtight). Is this a 90+ unit? If so, check drains hoses to make sure they are not plugged. Have you noticed any signs of water in or around furnace. How many pressure switches are on furnace? One or two, or possibley three.

mpinoly · Dec 25, 2008, 05:46 PM

It doesn't have a condenser, so no drains to check. It's a Trane XB80. I think there is only one pressure switch - it seems pretty straightforward, gas line coming in, switch, tubing out to burners, nothing else in-between. I'll check that hose though... thanks. The unit is about 5 years old.

mygirlsdad77 · Dec 25, 2008, 06:24 PM

So it has a metal vent? Should be easy to unhook vent from top of furnace. May need to remove a few sheet metal screws. Unhook vent, then see if furnace ignites. If it does, you have an obstuction in the vent. Do not, under any circumstances, run the furnace(other than for troubleshooting purpases) with the vent unhooked. Try this and let me know what you find.

Actually, before you try that, try this.

1. turn power off to furnace.
2. take hose between pressure switch and draft inducer off, at draft inducer(leave it connected to pressure switch).
3. turn power back on to furnace.
4. As soon as draft inducer starts to run, put the hose in your mouth and suck on it(not hard, just enough to keep the pressure switch closed), keep sucking on it for up to one minute. Let me know if the burners ignite. This test will tell a lot if done correctly.

mpinoly · Dec 25, 2008, 07:01 PM

The vent looks like it has something like rivets instead of screws - not sure I want to try and remove it and I'm not comfortable with the sucking tube idea. I think I'll just call tomorrow and let the pros look at it. I do appreciate the suggestions - thanks you.

mygirlsdad77 · Dec 25, 2008, 07:10 PM

Originally Posted by mpinoly

The vent looks like it has something like rivets instead of screws - not sure I want to try and remove it and I'm not comfortable with the sucking tube idea. I think I'll just call tomorrow and let the pros look at it. I do appreciate the suggestions - thanks you.

Calling for professional help sounds like the best bet in this instance. Please let us know what they find. Take care,

Lee

mpinoly · Dec 25, 2008, 07:49 PM

Will do. Thanks again.

Melanie

KC13 · Dec 25, 2008, 08:42 PM

Try this: disconnect hose from inducer housing, straighten a paper clip, and poke it through the hose fitting on the inducer housing to make sure it isn't clogged. Reconnect hose and try again.

KC13 · Dec 25, 2008, 09:38 PM

Oops! I gave away the paper clip trick again! Alas, another tech's kid will have to skip college and become an apprentice... I feel horrible!:(

MarkwithaK · Dec 25, 2008, 11:30 PM

Originally Posted by mpinoly

It doesn't have a condenser, so no drains to check. It's a Trane XB80. I think there is only one pressure switch - it seems pretty straightforward, gas line coming in, switch, tubing out to burners, nothing else in-between. I'll check that hose though ... thanks. The unit is about 5 years old.

Are you sure you are looking at the pressure switch and not the gas valve?

mpinoly · Dec 26, 2008, 11:47 AM

As I described it, you're right the gas valve... but the repairman just left and replaced the circuit board, which was fried. The pressure switch was fine it turns out.

Thanks to all for your time and suggestions! The house is warmin' up!

Melanie

mygirlsdad77 · Dec 26, 2008, 12:37 PM

Just another classic case of us not being there to put tester to equiptment. Glad you got it fixed. Stay warm, Take care,

Lee

mygirlsdad77 · Dec 26, 2008, 12:42 PM

Originally Posted by KC13

Oops! I gave away the paper clip trick again! Alas, another tech's kid will have to skip college and become an apprentice...I feel horrible!:(

If in 15 or so years I can't afford to put my girls through college, and they have to go through an apprenticeship under me, because you gave away this nifty little fix away, You will be hearing from me. On the other hand, I will save the expense of paying for college, and most likely make more money by having my children work for me. So keep up the good tips. Ive always said, someday I will have the cutest plumbers and hvac techs in the trade. Just have to convince them that poopie isn't gross.

KC13 · Dec 26, 2008, 02:21 PM

Let us know how that works out for you...

mygirlsdad77 · Dec 28, 2008, 04:51 PM

Im guessing not so good. Actually I would go bankrupt putting them through college before I would make them put up with the things we have to.

edwardvan · Jan 19, 2009, 10:55 AM

Thanks, this tapping solved my problem... XT80 error 3 flashes, no draft blower running until switch was closed. Just opening the compartment where the draft blower was may have unstuck the switch. All is good now.