Furnace Questions

ido1957

ido1957

9K Gold Member
I probably need a new furnace (it's probably 25 years old) but trying to avoid that as long as possible.
I just had a guy come in and replace the motor, wheel and clean the sensor. The fan would start, no flame at all then it would shut off.
So that cost me 550 bucks to fix.

Today I noticed a problem that has occurred prior to this fix. The thermostat is one of those digital 7 day programmable ones by LUX. I'll wake up and the thermostat is set to 20 but the house 17 degrees. So I turn the thermostat down to 16 and then up again - as soon as it hits 17 it clicks and I hear the blower start. So I go downstairs and watch what happens. There is a yellowish flame of some kind first (quite bright), and the fan is running. Then a big click and some sort of noise maybe a whooshing sound, then the yellow flame goes out and the gas kicks in and the main burners start - and stop after a second or two. Blower keeps going and this sequence repeats 3 times before the main burners stay on and everything seems to work ok.

It seems likely that this start/stop thing is happening in the morning but is basically failing. I'm going to guess it's three strikes you're out. The furnace will not kick in until I make it as described above.

I can buy a service plan for 25 a month which covers pretty much everything. I'm heavily considering this to get me through next winter - while I save up for a new furnace (or part of it at least). There's a deductible, waiting period blah blah blah.

Anyone have any experience with this start/stop problem? I do not want to call them up (and complain about warranty) as I'm worried that they will just come out and say I need another 500 bucks worth of work. If I buy the service plan and wait a month I can get them to come out and look at it and maybe fix it for whatever the deductible is (I hope). Plus three more months until the furnace is really needed. I would like to know why it does this - especially since I just had a guy and I told him that was part of the problem.

PS - I live in Canada so the furnace kicks in even in June :D
 
'Yellow flame' - pilot light? Assume this is a gas furnace!
If the pilot goes out, but you say 'the main burners start ' - so you can see the lines of flame along each burner row? And then it shuts off? Find another furnace guy, if he won't make good on the repair.

You're in Alberta - so you're paying about $100 a month for gas even in the winter, right? (bastard ;) ) If this is gas, and it still uses a pilot light, its time to replace the whole furnace - should have done that before spending the $550 repair. New gas furnaces don't use a pilot light and are about 10X as efficient as those from 1990.
 
Yes it's a natural gas furnace and we pay about 100 a month for gas. That will probably go up 50% after the Carbon tax kicks in this January $#$%^

The blue flames start up along the burners momentarily then shut right down after a split second - I'm assuming there's some issue with the sensor.

Now that I think of it, I had a repair guy out back in the winter and he cleaned the sensor. When the most recent guy came out he said it was really black - what would cause the sensor to get so dirty so quick? I had it replaced a couple of years back and it was fine for a while.

I'm going to get a new furnace next year but for now I'm probably going to get that service plan just to keep it going. I may end up having to get a furnace anyway - just trying to postpone it as long as possible.
 
I had a very similar issue with my furnace recently. Exact same symptoms. I initially thought it was the flame sensor but a new one didn't fix the issue. It was one of two things. Not sure which one fixed it. I got advice from a HVAC guy by posting on FB.

On mine there is a pressure switch that has a hose running to it. The hose was split at the end slightly so air was leaking a bit. Check that. It could also just be the pressure switch itself that is bad. Not the case with mine.

Second was to pull every connection to the control board one at a time to make sure the connections are solid.

One of these things fixed my furnace.

Good luck!
 
Looked a little closer and it looks like the burner that heats up the sensor is not firing (and the one beside it but it's tough to see with the grate on).
There's four burners and two appear not to fire when this start / stop occurs. It tries 3 times then shuts off the fan and everything else.
Not sure why it's not firing sometimes and not others - maybe dirty. I did find a piece of debris on the top of the burner apparatus just above the sensors burner.
Looks like sloppy work by the guy that replaced the motor.
Photo1370.jpg
 
Dirty sensor in short time may be lack of air for proper combustion, which might be from a mis-adjustment. Gas flame usually blue. Yellow may be lack of air possibly.
Whooshing sound perhaps a build up of gas which hasn't ignited on the initial startup and finally catches. If this is the case, potentially very dangerous.
Is the exhaust flue clear?
Do you have the documentation for the furnace which might have a troubleshooting guide? Maybe found online at the manufacturer.
Do you have CO detectors in the area of the furnace and rest of the house?
 
arcaxis said:
Do you have CO detectors in the area of the furnace and rest of the house?
Click to expand...
That should be the first thing you do. Gas appliances can and will produce CO without smoke and kill you dead when you don't even know it. Oil-fired stuff makes lots of smoke with the CO so you will not likely die by surprise.
 
I have a CO detector in my furnace room. That is great advice that I just assumed ido had.

It does now sound like an issue with something blocking the gas to your burners if all of them are not lighting up at once.

I would say either try to clean them out, or get that thing replaced if you want warm air come winter. Strange though as natural gas burns really clean. Not sure what would cause a blockage of the supply to the burner tubes. Maybe you have large bugs in Canada that like to nest in your heater? lol

That brings up a somewhat uneducated thought that maybe the gas regulator is not giving enough pressure to fire all burners. I would look into that first now that I hear this. I had a gas cooktop once that the regulator took a shit and the flame would barely boil water.
 
Just a thought about gas fired stuff. My neighbor was a plumber with about 30 years in the trade and knew what he was doing real well. He was doing an install and test of a furnace system last year in a new house. He was working alone. At some point while checking the thermostat the furnace failed to fire and evidently a safety sensor did not function properly and did not stop the gas flow. Gas built up and supposedly was unnoticed in the part of the house he was in. A gas hot water heater pilot light triggered an ignition of the gas which exploded. He came out of it with 90% of his body burned and passed away about 14 days later. The explosion lifted the house off the foundation.

There's not much in my house I won't work on. If I had gas in my house, which I won't ever, it's probably the one thing I wouldn't touch other very minor maintenance. Too much at risk to play with something like that unless you're 100% sure of what you're doing.
 
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