My furnace is acting screwy

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HAHA THE MOOSE

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chicagoland burbs
I know this is not a HVAC forum but I was hoping one of you knowledgeable tradesfolk would be able to help me out. I checked with other forums on the net (one's that claimed to be a HVAC forum but people post to it like twice a month). So anyway I have a Fridgidaire model # C3BA-030C-A. It was installed in 2002 and has been working fine (except for the blower wheel coming loose in 2006 which was such a pain in the A#$) until last winter when the flame sensor started giving me problems. Well I took it out and gave it a light sanding put it back in and just like that worked as good as new. Well this winter I started having a new problem (the furnace gave me a code which said "limit circuit open or external load on W") which was that the fan and the blower would turn on but the ignitor would not click on (light up). So the first thing I did was check voltage (line voltage connections first then low voltage) across the board which checked out ok. I then checked ever single limit switch on the furnace which checked out ok (continuity was all good). The last thing I did was to make sure the back side of the board was ok. I took a magnifying glass to it and looked for any soder points that looked bad. Well I saw 3 on the same 9 pin connector that didn't look like all the other. Instead of having a tip (sorta lookin like a nipple) it was indented (sorta like a donut). I took a sodering pen and filled in these three connections. When I put the board back on the furnace fired back up. Well that worked for a couple of days but now I have another problem. Everything seems to cycle fine up until the ignition. The ignitor glows hot, the flame starts but turns of in a second or two. So I guess what my long winded question is could this just be a bad board and i'm screwed or maybe the flame sensor has gone bad. I don't know how to check that. Its just one wire onto a metal piece that goes in-front of the burners. It should be 120v according to my schematic but I don't have any voltage on it, i'm thinking its just an intermittent voltage for when its actually sensing. Oh ya and I changed my t-stat. If anyone has any ideas that may help me solve this I would greatly appreciate it, because I am out of ideas. I'm am not experienced working with circuit boards and my HVAC skills are pretty limited, and if it is the board can I purchase a new one online and will it be identical port to port. Unfortunately I don't know any HVAC tech's well enough and the ones that I do work with to me seem for like installers rather then knowledgeable technicians.

Thanks for your time. Sorry this post was so long.
 
Check your flame sensor again, particularly the crimp connection where the wire connects to the rod.

DO NOT clean the rod with sandcloth. The grit dust can actually melt onto it and form a ceramic-like coating. Use a stainless steel toothbrush that TIG welders prepare their joints with. Or, replace the sensor rod.

What's your flash code saying when you let the unit lockout?
 
I know this is not a HVAC forum but I was hoping one of you knowledgeable tradesfolk would be able to help me out.
I checked with other forums on the net (one's that claimed to be a HVAC forum but people post to it like twice a month). So anyway I have a Fridgidaire model # C3BA-030C-A.

It was installed in 2002 and has been working fine (except for the blower wheel coming loose in 2006 which was such a pain in the A#$) until last winter when the flame sensor started giving me problems.

Well I took it out and gave it a light sanding put it back in and just like that worked as good as new, Well this winter I started having a new problem (the furnace gave me a code which said "limit circuit open or external load on W") which was that the fan and the blower would turn on but the ignitor would not click on (light up).

So the first thing I did was check voltage (line voltage connections first then low voltage) across the board which checked out ok. I then checked ever single limit switch on the furnace which checked out ok (continuity was all good), The last thing I did was to make sure the back side of the board was ok, I took a magnifying glass to it and looked for any soder points that looked bad. Well I saw 3 on the same 9 pin connector that didn't look like all the other.

Instead of having a tip (sorta lookin like a nipple) it was indented (sorta like a donut). I took a sodering pen and filled in these three connections. When I put the board back on the furnace fired back up. Well that worked for a couple of days but now I have another problem. Everything seems to cycle fine up until the ignition. The ignitor glows hot, the flame starts but turns of in a second or two.

So I guess what my long winded question is could this just be a bad board and i'm screwed or maybe the flame sensor has gone bad. I don't know how to check that. Its just one wire onto a metal piece that goes in-front of the burners. It should be 120v according to my schematic but I don't have any voltage on it, i'm thinking its just an intermittent voltage for when its actually sensing.
Oh ya and I changed my t-stat. If anyone has any ideas that may help me solve this I would greatly appreciate it, because I am out of ideas. I'm am not experienced working with circuit boards and my HVAC skills are pretty limited, and if it is the board can I purchase a new one online and will it be identical port to port. Unfortunately I don't know any HVAC tech's well enough and the ones that I do work with to me seem for like installers rather then knowledgeable technicians.

Thanks for your time. Sorry this post was so long.
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....................................
 
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I'm no hvac tech so this is just a blind shot in the dark, but flame sensor/thermocouple might be bad - its worth the 20 bucks to try it anyway before you spend the money for a service call, but that would be next.
 
I would call a HVAC service company.
Oil furnaces ain't nothing to play with, right up there with gas furnaces. It ain't worth the possible danger.
How many times do we say that about electrical problems.......
 
Agreed, or you can check the flame sensor by installing a new one. Some of them use bi-metal. I changed one on my gas fire place, and it started working.
I am not an HVAC guy either. :smile: Good Luck
I hope it works, those boards can cost a bunch.
 
qcroanoke said:
I would call a HVAC service company.
Oil furnaces ain't nothing to play with, right up there with gas furnaces. It ain't worth the possible danger.
How many times do we say that about electrical problems.......
Click to expand...
The guy is working on a gas furnace. The Fridgidaire model # C3BA-030C-A is a really tiny furnace too. I didn't know they made a model that small.

EDIT>> that model is not the furnace. That's the model of the A/C coil. :) The 030 was screwing me up, thinking that was a 30,000 BTU furnace, until I looked up the part number in my guide.
 
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Thanks everyone for your responses I greatly appreciate it. I did clean the sensor with a 180 grit sand paper and maybe that has screwed it up. I'm gonna try and replace the sensor with a new one if that does not work I guess I'll just bight the bullet and for the first time in my life call in someone to look at my broken stuff. I was hoping to go a lifetime without doing that but its gonna get cold and my girlfriend is gonna get even more craby. So thanks a lot and hopefully that will fix it. Have a good night all.
 
Oh, and make sure you have a healthy blue flame hitting the sensor.
A dirty pilot tube can be cleaned with a bicycle tire pump.
 
HAHA THE MOOSE said:
Well this winter I started having a new problem (the furnace gave me a code which said "limit circuit open or external load on W") which was that the fan and the blower would turn on but the ignitor would not click on (light up).
Click to expand...

I am not familiar with Frigidaire products, but it sounds to me like a flame roll out limit is open. Most of them have a Manuel reset button. Either that or there is something grounding the White thermostat wire.
 
Check the sail switch by temporarily jumping it out as it wont operate with the unit disasembled confirming the gas purge cycle before ignition. I have seen this cause problems occasionally.
 
stickboy1375 said:
Well that worked for a couple of days but now I have another problem. Everything seems to cycle fine up until the ignition. The ignitor glows hot, the flame starts but turns of in a second or two.
Click to expand...
First question: Natural Gas or LPG (propane)

I was experiencing something similar to what you describe about a month ago with my propane furnace. (When it happened to be -22?C outside) It would go through all the motions of igniting, one of the four venturi burner tubes would ignite, then after 10 seconds it would shut off the gas, wait a few minutes, and try again. After 4-5 attempts it would give up and go into blower mode.

My unit is installed on it's side, so the 4 burner tubes are in a row vertically. The glow plug / ceramic ignitor thingie is in the top most burner, and the actual flame sensor was in a lower tube. The upper most tube would light but others wouldn't catch before the board shut off the gas and tried again.

Anyways, HVAC tech came out and pulled out the burner manifold. Evidently, in addition to the 4 burner jets, there are also some long thin slots that allow the flame to propagate from one burner to the next. These get clogged with soot, etc, and the thing won't light properly. I can't remember exactly what he said he did but it was something along the lines of cleaning out these slots with a feeler gauge, plus cleaning out the jets. He made it sound like a normal occurrence for propane furnaces given the impurities in the gas.
 
quogueelectric said:
Check the sail switch by temporarily jumping it out as it wont operate with the unit disasembled confirming the gas purge cycle before ignition. I have seen this cause problems occasionally.
Click to expand...

That being the case, the flashing code would indicate either a failure with the induced draft blower or a pre/post purge failure. Is the little fan motor running?
 
Rampage_Rick said:
My unit is installed on it's side, so the 4 burner tubes are in a row vertically. The glow plug / ceramic ignitor thingie is in the top most burner, and the actual flame sensor was in a lower tube. The upper most tube would light but others wouldn't catch before the board shut off the gas and tried again.

Anyways, HVAC tech came out and pulled out the burner manifold. Evidently, in addition to the 4 burner jets, there are also some long thin slots that allow the flame to propagate from one burner to the next. These get clogged with soot, etc, and the thing won't light properly. I can't remember exactly what he said he did but it was something along the lines of cleaning out these slots with a feeler gauge, plus cleaning out the jets. He made it sound like a normal occurrence for propane furnaces given the impurities in the gas.
Click to expand...

That would give a flame failure code.
 
For what its worth, check the ignitor and make sure there are no cracks in it. Not sure how your unit compares to others, but I've had mine malfunction because of that.
 
stickboy1375 said:
I know this is not a HVAC forum but I was hoping one of you knowledgeable tradesfolk would be able to help me out.
I checked with other forums on the net (one's that claimed to be a HVAC forum but people post to it like twice a month). So anyway I have a Fridgidaire model # C3BA-030C-A.

It was installed in 2002 and has been working fine (except for the blower wheel coming loose in 2006 which was such a pain in the A#$) until last winter when the flame sensor started giving me problems.

Well I took it out and gave it a light sanding put it back in and just like that worked as good as new, Well this winter I started having a new problem (the furnace gave me a code which said "limit circuit open or external load on W") which was that the fan and the blower would turn on but the ignitor would not click on (light up).

So the first thing I did was check voltage (line voltage connections first then low voltage) across the board which checked out ok. I then checked ever single limit switch on the furnace which checked out ok (continuity was all good), The last thing I did was to make sure the back side of the board was ok, I took a magnifying glass to it and looked for any soder points that looked bad. Well I saw 3 on the same 9 pin connector that didn't look like all the other.

Instead of having a tip (sorta lookin like a nipple) it was indented (sorta like a donut). I took a sodering pen and filled in these three connections. When I put the board back on the furnace fired back up. Well that worked for a couple of days but now I have another problem. Everything seems to cycle fine up until the ignition. The ignitor glows hot, the flame starts but turns of in a second or two.

So I guess what my long winded question is could this just be a bad board and i'm screwed or maybe the flame sensor has gone bad. I don't know how to check that. Its just one wire onto a metal piece that goes in-front of the burners. It should be 120v according to my schematic but I don't have any voltage on it, i'm thinking its just an intermittent voltage for when its actually sensing.
Oh ya and I changed my t-stat. If anyone has any ideas that may help me solve this I would greatly appreciate it, because I am out of ideas. I'm am not experienced working with circuit boards and my HVAC skills are pretty limited, and if it is the board can I purchase a new one online and will it be identical port to port. Unfortunately I don't know any HVAC tech's well enough and the ones that I do work with to me seem for like installers rather then knowledgeable technicians.

Thanks for your time. Sorry this post was so long.

....................................
Click to expand...

Hey, your post is just like HAHA's, except with paragraphs. :D
 
Good morning,
Make sure your unit doesn't have a air proving switch, Check the schematic, if it is clogged or block the unit could attempt to start but if it can't see the blowers air flow it could shut down.

LHarrington
 
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