Need help with Furnace

**x00018** · 01-08-2009, 06:15 AM

Furnace problem

That sounds like the same thing I had with mine last year. The electronic ignitor was getting weak and would not light the flame when it started up. The safety would shut the furnace down and turning the breaker off and on would reset it. I replaced the ignitor and it has worked fine since.

Good Luck
Dave

**cgallery** · 01-08-2009, 06:50 AM

Something is tripping the safety. By power cycling, you're resetting and allowing the furnace to try again.

You're going to have to be there one of these times when it tries to start, and can't. Sometimes you can get an audio or visual clue as to what is going wrong.

The ignition system on my very old Carrier requires that I clean it out with compressed air once a season. One of these days I'm going to have to take it apart and clean the pilot tube with some piano wire.

Your system may be new enough that it keeps track of a diagnostic code that can be read somewhere. I'd google the model of your furnace + "troubleshooting" and see what comes up.

**iceman61** · 01-08-2009, 07:23 AM

I don't know if this is your problem or not but my split unit has a safety system installed in the exhaust vent pipe that gave me a similar problem a couple of years ago. A friend of mine that is in the repair business told me what to check & it saved me a couple of hundred dollars on a service call.

On split units where the heat section is in the house there is a blower the is installed in the exhaust vent pipe. It's function is to clear out any lingering gas fumes before initial ignition avoiding a possible explosion. There is a small 1/8" hose that comes off of this blower that goes up to a control relay. If this tube becomes blocked it will fool the relay into thinking there is gas in the combustion chamber & the unit will not come on, although the exhaust blower will cycle on & off several times.

Personally, all I had to do on mine was to take a small drill bit & hand thread it through the small barb where the hose attached to the blower & clear the obstruction. I did go one step farther & took the blower off & cleaned it out. It seems that condensation had caused some scaling inside the blower & a very small piece of the scaling had blocked the port.

**herb fellows** · 01-08-2009, 07:30 AM

Or.. you could simply have a thermostat gone bad. At a cost of $40-$60 for a new programmable one....

**iceman61** · 01-08-2009, 08:02 AM

Originally posted by cgallery

Your system may be new enough that it keeps track of a diagnostic code that can be read somewhere. I'd google the model of your furnace + "troubleshooting" and see what comes up.

Most of the newer units will flash a code via a small LED. The service department at the Manufacturer can tell you what the codes are although they usually tell you that they only give out the codes to a licensed contractor. If you were to tell them you are a contractor they will probably give you the codes over the phone. They did for me anyway.

**mschrank** · 01-08-2009, 05:59 PM

I had that problem with my old furnace, and it happened earlier this winter with my new carrier. In both cases, it would fire up and burn for a brief time, then snuff out. Turns out that the units weren't getting enough combustion air. On my new unit, it was because snow was getting sucked in and clogging on the pest screen.

If your setup is like mine, you can test for this by disconnecting the rubber coupling that couples the intake pipe (usually a 3-4" PVC pipe) to furnace. It probably has a couple of radiator hose clamps holding it in place. Undo them and move the coupling so the furnace can draw air straight from the room it's in. Don't worry, this is safe...just make sure you undo the INTAKE and not the EXHAUST! If it works after you try this, you've probably got a clog somehwere in your intake pipe.

My Carrier has a yellow LED that flashes a combination of short and long flashes that correspond to numbers and explanations printed on a big sticker on the inside of the removeable panel. Mine's brand new, so it may be something they started doing recently.

**Thalermade** · 01-08-2009, 06:05 PM

Thanks for all the info folks. As time permitted today I perused a number of sites on the internet. Found some great information and a site or two to buy parts from if necessary.

I had completely forgotten about the LED diagnostic codes. Of course the window you look through is located a foot above the floor, with the code chart that has a font size too small for ants to read without a magnifying glass. Or maybe it is my aging eyes in a dimly lit room....

Anyway got home from work and the furnace was working fine. I did go ahead and do a quick inside vacuum and cleaned off the flame sensor rod (thanks master53 yoda).

I'll keep you posted.

Russ

**master53yoda** · 01-08-2009, 08:43 PM

furnace problem

If the combustion vent is PVC pipe.

1. make sure that snow is not blocking either the intake vent or the outlet vent
2. verify that the drain tubing coming from the furnace is not blocked.
3. Make sure the air filter is clean. If you have used one of the new high efficiency filters they plug and reduce the air flow enough to set the high limit off. Clean once per month.
4. clean the 1/8 th inch flame sensor rod if it is corroded

5. the problem is not the thermostat if turning off the furnace resets the control.

Retired HVAC tech and instructor

art

**Thalermade** · 01-09-2009, 10:53 AM

Originally posted by master53yoda

If the combustion vent is PVC pipe. No, all metal.

1. make sure that snow is not blocking either the intake vent or the outlet vent. No snow at this time
2. verify that the drain tubing coming from the furnace is not blocked. Tubing clear
3. Make sure the air filter is clean. If you have used one of the new high efficiency filters they plug and reduce the air flow enough to set the high limit off. Clean once per month. Filter is clean
4. clean the 1/8 th inch flame sensor rod if it is corroded. Nice and clean now

5. the problem is not the thermostat if turning off the furnace resets the control.

Retired HVAC tech and instructor

art

Thanks Art, This is probably my usual situation of having an intermittent problem I have to deal with for a few weeks before the complete failure occurs.

The furnace has been working correctly since yesterday afternoon - knock wood.

Russ

**master53yoda** · 01-09-2009, 11:43 AM

furnace problem

When the combustion vent is metal it means that the furnace is an 80+ efficiency furnace but not condensing.

That limits the problems to the flame sensor rod that it appears that you have cleaned. Or the high limit.

Are you using the newer pleated high efficiency filters. They are notorious for causing air flow restrictions. They were originally designed for fans that could develop 1.5" static pressure or more as a furnace can only develop 3/4 " static pressure the furnace can't work against a dirty pleated filter.

Art

**Thalermade** · 01-09-2009, 06:14 PM

Originally posted by master53yoda

When the combustion vent is metal it means that the furnace is an 80+ efficiency furnace but not condensing.

That limits the problems to the flame sensor rod that it appears that you have cleaned. Or the high limit.

Are you using the newer pleated high efficiency filters. They are notorious for causing air flow restrictions. They were originally designed for fans that could develop 1.5" static pressure or more as a furnace can only develop 3/4 " static pressure the furnace can't work against a dirty pleated filter. Art

I figured out that the model #8000 related to the 80 efficiency rating.

As for the filter, I use a washable that that still looks to be in great shape.

Thanks again.
Russ

Need help with Furnace

Need help with Furnace

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