Stupid furnace, need advice please!

[Jay5.9L]

Last Thursday night/Friday morning I woke up to a very cold house and a grumpy 8 month old. Had to go out and get a replacement draft inducer motor (which was an adventure all by itself). Got everything replaced and running well.

Over the last few days the furnace will work just fine but at random it will not kick over when the thermostat calls for heat. A quick power cycle and the furnace will start right up. Any ideas what could be causing the erratic behavior? It also was heating for a while when both thermostats (one standard Honeywell dial for up stairs, one new programmable Honeywell for down) were not calling for heat.

The home was built in 1997 and has a Carrier furnace/AC and yes I did replace the filter

 

[offroaddave]

Every year I take the air compressor and the shopvac to mine, wether it needs it or not. :-\

 

[MR.CJ-7]

not sure. I had a similar thing happen to mine last week. I woke up to a cold house, grumpy baby and grumpier wife.

The furnace was running, but blowing cold. Turned out to be a switch on the flame sensor switch. Mine was pretty simple to diagnose, it has an LED that blinks a code. Does yours have anything like that?

Good luck!

 

[Drew_XJ]

you said something about 2 thermostats? are they on seperate system or is your system zoned?

 

[Jay5.9L]

I did a big vacuum a while ago so the unit it pretty clean.

2 thermostats on the same system. There is a little control panel (that I believe controls a damper or maybe 2 fans, not sure how it works) to control where the hot/cold air goes. The upstairs is the standard dial that came with the house. The downstairs is a brand new programmable unit that I installed a few weeks ago and ran just fine until the draft inducer motor went belly up.

 

[yellowbronco]

When you replaced the draft inducer motor, you more than likely had to remove a vacuum line to a pressure switch. Sometimes those are a little finicky, make sure it's plugged in good. Worst case scenario would be the control board, erratic behaviour can sometimes be attributed to that. Of course there's a myriad of other things that can cause similar symptoms.

 

[Jay5.9L]

Took a better look and its a Carrier 2 zone controler.

And there were only 2 wires connected to the inducer and yes they are back on the correct terminals (I took pictures before I started tearing it down just in case).

Some one told me to turn the unit off for a while so it can loose its memory and rest. Its been off for about 30 min so wish me luck

 

[richpblaze]

Change your filter

See if that helps.

 

[Jay5.9L]

Well I turned the unit off for about 30 min. Turned off the dial stat, took the batteries out of the programmable stat. Reinstalled the batteries, reprogrammed and turned the stat off.

Turned on the furnace. turned on both stats.

Ran all night fine then this morning I had to power cycle the damn thing again

 

[richpblaze]

Change your filter

If it's not getting enough air it will shut itself off.

 

[Meat_]

If it's not getting enough air it will shut itself off.

He said he changed it in the first post.

 

[Jay5.9L]

Yup new filter maybe 2 weeks ago. The things works just fine for hours then at random won't kick over.

 

[richpblaze]

Have you been doing any work (dust)???

You would be suprised at how fast a filter will clog up. Blow it out with compressed air and see what happens. Also blow out the unit and everything, open both doors and either vacum or blow it out. My .02

 

[Drew_XJ]

so its a carrier furnace you should be able to trouble shoot it using the diagnostic codes on the board. what you need to do is take the lower door off the unit( it has a door switch on it and it will have the board inside) hold the door switch closed and call for heat from one of your t stats. When it fails to fire off it will blink a code on the (amber i think) l.e.d on the board the codes should be on the back of the lower door you removed

 

[redrockcrawler]

it is probably the flame sensor is dirty look on the burner rail for a small rod with ceramic on top and one wire on it undo the screw and pull it out take some sand paper and scuff it up and re install

the reason you reset it is it will lock out after flame signal is lost 3 times but a low signal will be an intermittent problem like you described

 

[yellowbronco]

Strike all these posts!!!! Wrong, all of them!!!



It's the Flux Capacitor!

 

[Jay5.9L]

Strike all these posts!!!! Wrong, all of them!!!



It's the Flux Capacitor!

Of course!!!!!! Now where did I put that box of plutonium???

Seriously thanks for the info. After resetting it Tuesday morning its been running fine. It does cycle more than I like but I attribute it to the programable thermostat trying to keep the temp with in 1 deg of set point. I'll take some compressed air to it this weekend and look for the flame sensor as well.

 

[Jay5.9L]

Drew and redrock were on the right track. It cut out again last week and I saw the little light blinking a code. It pointed to a ignition problem and one of the causes could be a dirty flame sensor. A little light sand paper on the sensor and a few shots of compressed air and I think its fixed. Thanks for everyone's help!