Furnace Misbehaving? This may help.

**Nightprowler** · 11-10-2015, 08:42 PM

Yesterday evening we got home and the house was cool. We had been turning it on and off according to the weather, so I thought maybe it had been turned off. This morning it was a little to cool for these old bones, so I went to turn it on at the thermostat. The temp reading was 63, but set at 68. I had to get to work, so I went to the electric panel and turned it off for 30-seconds, then switched it back on. I heard it start up and things sounded normal. As I went out the door, I heard it kick off (not at 68).
Got home this evening and checked things out. Looking at the front of the furnace, you'll see a clear peep hole.

Inside you will see a red light. The led light blinks a code. There will be a long pause, then a number of blinks followed by another number of blinks. This is the code that your furnace is letting to know what is wrong. My code was long pause followed 3-blinks followed by 4-blinks (led code 34).

One symptom of #34 is Oxide buildup on flame sensor (clean with fine sandpaper).
Lift the top portion off with help of a screw driver to pry up.

This what my upper portion looks like.

The blue flame kept kicking on but won't stay on for more than 15-20 seconds. It would try again (3 times) and then shut down. Next, I removed the lower cover, which shut the power off with this switch.

This what my lower portion looks like.

You can observe the board for any MR. OBVIOUS problems. (burnt, discolored, bad odor, ect)

Mine looked good so I moved on to the flame sensor. The flame sensor is located somewhere around the burner tubes. It is electrical, so your looking for a single wire. Mine is (white wire) located below the burner tubes.

A simple 1/4" socket is needed to remove one hex head screw. Turn it to the left to unscrew and turn right to re-tighten later.

This is my flame sensor. It didn't look bad or any build up. I took a dollar bill cloth and sanded the sensor. Be sure to not touch it, which adds oil.

Reinstalled the sensor. Put the covers back on and life is back to good.

30-min fix, including clean-up. Hope this helps and saves you from paying a service tech your hard earned cash. Now you can donate it at a crappie tourney coming to your neighbor hood.

BE SMART AND TURN THE FURNACE POWER OFF AT THE BREAKER BOX.
BE SMART AND SAFE!
Heading back to the couch.

**Redge** · 11-10-2015, 09:23 PM

Nice write up, I enjoyed it.

**doggone** · 11-10-2015, 10:45 PM

How do you expect us furnace techs to buy crappie jigs...buy boats...and gas to get there if you everybody keeps fixing there own stuff huh???...what about that??? LOL.

Sometimes you need to clean the burner face closest to the flame rod. The integrated circuit board applies an a/c current to the flame rod....when the flame touches it the current flows through the flame to the burner face which allows the current to flow back through ground to the board.As the current flows through the flame it is rectified to DC.The board is looking for that DC current flow.So anything that impedes that circuit whether it be the connection to the rod,material on the rod,or rust on the metal its grounding too can all affect it.

**Slabyanker** · 11-11-2015, 02:24 AM

I've had that problem too. I have to do it every other year or so.:thumbup:

**Nightprowler** · 11-11-2015, 04:31 AM

Originally Posted by doggone

How do you expect us furnace techs to buy crappie jigs...buy boats...and gas to get there if you everybody keeps fixing there own stuff huh???...what about that??? LOL.

Sometimes you need to clean the burner face closest to the flame rod. The integrated circuit board applies an a/c current to the flame rod....when the flame touches it the current flows through the flame to the burner face which allows the current to flow back through ground to the board.As the current flows through the flame it is rectified to DC.The board is looking for that DC current flow.So anything that impedes that circuit whether it be the connection to the rod,material on the rod,or rust on the metal its grounding too can all affect it.

Thanks for the added info. Its good to know.
Furnace Techs are needed for the harder stuff. I just don't want them to have a bigger boat then mine...

**INTIMIDATOR** · 11-11-2015, 10:05 AM

Had the same problem last Winter...my flame sensor wire had come loose from the box (??)....tightened it up and all was good!
And Yes, I went ahead and cleaned the sensor, vacuumed it all out, and changed filters.

**KDAVID1** · 11-11-2015, 08:32 PM

Went through that last year. Bad capacitor, then bad blower, then bad panel, then bad flame sensor. Everything is new except the burner and gas valve but it works good--hopefully for another 13 years

**Cricketcage** · 11-12-2015, 12:39 PM

Great information. I had the same problem last month except that the wire from the flame sensor had gotten pinched by the lower panel and was shorting the signal to the chassis. Moved the wire and it's been working fine since. Just saying this to encourage people to check the path to the board if cleaning alone doesn't work. I cleaned mine and then replaced it (only $12), before I bothered to look any further.

**Hanr3** · 11-16-2015, 09:52 PM

It's a good thing to have a HVAC expert in the family that you can swap services.

I have a riding mower I'm giving him, ought to buy me a few service calls.

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