Furnace won't stay on. Have to reset.


  #1  
Old 11-26-12, 12:52 AM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Furnace won't stay on. Have to reset.

Hi. I live in Kelowna, BC Canada. Its been a mild winter up until recently so I don't really know how long this has been a problem. I want to say it "just started" but maybe not. Furnace is a Tempstar SmartComfort (model? where is it??). House built in 2007 so the furnace is 5-6 years old along with everything else.

Last few days we've been waking up to c-c-c-cold! Thermostat said it was set to 20 (celcius) but currently 16 and getting no warmer. Eventually I realized the furnace wasn't really on... just cycling the fan every once in awhile. I saw the blinking light and the codes on the inside cover. 6+1 flashes indicates a "soft lockout" after repeated ignition failures.

I did some reading and something suggested I short R+W to act as the thermostat. That appeared to work and it fired properly. The advice indicated that proved it was a faulty thermostat so I bought a new one. No luck. It worked for a bit, but went back to 6+1 after awhile.

If I don't do anything once the problem begins, and I just observe... I see it will try to come on approximately every 5 minutes. The fan will run for 2 minutes, during which time the glow plug glows very bright and I get a small blue flame around it but the gas doesn't "kick in". After about 10 seconds, the glow plug turns off and it tries again one more time, then we wait another 5 minutes.

If I shut the power off and turn it back on in short order, we get the same thing.

If I shut it off for an extended amount of time (8 minutes is the shortest I tried that worked), then she's back to normal (for the time being) and the glow plug glows followed very quickly by a "click" and the gas fires and Bob... as they say... is your uncle. Then it seems to operate normally "for a while" (I haven't yet identified why or when it stops working again). Some point later on, we're back to a 6+1 though.


So my uneducated guess is the flame sensor isn't telling the system that the flame is there, so the gas never fully turns on. Though I suppose it could be the "smart" pc board just not listening to the sensor. I don't think its whatever turns on the gas, since that reliably works again after a reset.

Its pretty cold in here. Thankfully we have a little oil heater for the baby's room. I hesitate calling a pro right now... just don't have the cash. So if this is DIY-able, great. If not, I'll figure out something and call someone. I can't really afford it right now, but I also don't want to be in a situation where not calling now costs me more down the road.


Some things of note:
- We had the furnace "cleaned" this summer by a duct cleaning service who convinced me we didn't need to get the furnace "serviced" because his cleaning does a better job anyway. I wonder if his "cleaning" knocked something.
- We temporarily had a couch blocking a cold air intake and that's right around the time it got cold and we noticed the problem. Once I realized that, I corrected it... but the problem persists. Could have have caused an over-heat that damaged something?
- The baby started dropping things down the registers so I got pre-cut pieces of filter material that's designed to fit in registers. Could that be affecting airflow and causing this?


Thanks.

- Steven

ps. No HVAC training at all, but I'm reasonably handy with both mechanical and electrical.
 
  #2  
Old 11-26-12, 01:29 AM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 5,499
Likes: 0
Received 1 Like on 1 Post
>


Please describe this in more detail. It sounds like the gas for the burners is switching on, but not with the pressure needed to light the burners properly.

Do you use propane or natural gas?

Do you have other gas appliances, and if so, are they operating properly?

If you do, see if they light up correctly when the furnace is failing to light properly.

(You could have inadequate gas pressure to light the furnace some of the time. If that's the case, other appliances would be affected if the gas supply to the house is the problem.)
 
  #3  
Old 11-26-12, 05:20 AM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,568
Received 50 Likes on 46 Posts
I serviced a 2004 Tempstar a few weeks ago that had a pilot tube coming from the Honeywell Smart valve.

The ignitor, pilot and sensor were mounted together making this the least serviceable modern furnace that I have seen in a while. Looks like it would be very easy to break the HSI if you service the sensor or pilot.

Be careful...
 
  #4  
Old 11-26-12, 08:47 AM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
I don't think its gas pressure, though I can see why you might suspect that given my description. It is natural gas and other appliances are working fine. The furnace does too... after a hard reset (power off for a few minutes). Its whatever "triggers" the gas to come on full pressure (or whatever) that seems to be the problem. The more I read, the more I suspect the flame sensor because in layman's terms, it seems logical: the glow plug heats up and ignites a small amount of gas, but the sensor isn't detecting the flame so (for safety sake) the gas doesn't come on full bore because there's nothing to burn it (according to the sensor). It tries a couple times, and fails with a 6+1. All makes sense, except for the fact a hard reset always works. That makes me then think its the pc board not getting the message rather than the sensor not sending the message. Unless there's some (dangerous) reason that the system doesn't wait for the sensor on the first try after a reset?? That would seem supremely stupid though.
 
  #5  
Old 11-26-12, 08:50 AM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Looks like it would be very easy to break the HSI if you service the sensor or pilot
"HSI"? I tried looking that up on Acronym Finder and I've narrowed it down to "Hot Surface Ignitor" and "Harsh Squirrel Interaction"
 
  #6  
Old 11-26-12, 10:57 AM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 5,499
Likes: 0
Received 1 Like on 1 Post
Well, of course if this is a Honeywell "Smartvalve," that's likely the problem. As Houston describes, it tends to be an ignition system that has a lot of failures, the only lemon Honeywell has in the field of furnace controls.

The Honeywell Smartvalve lights a small pilot light each time the furnace is lit, which is likely the "small blue flame" you described. Iwas supposing you had a more common ignition system which doesn't have that pilot light.

Post the make and model of the electric gas valve so we'll know for sure.

And HSI means hot surface ignitor, an electrical heater that gets white hot to light the gas instead of using a spark or other method to light the gas.
 
  #7  
Old 11-26-12, 02:15 PM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
I'm not even sure what part he "valve" is exactly, but there's agreen tag attached to the igniter/glow plug's wires that says
Honeywell
Replace with
Q3400A 1024
Assembled in
Mexico
0450
 
  #8  
Old 11-26-12, 02:50 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,568
Received 50 Likes on 46 Posts
(model? where is it??)
If this a (left to right) horizontal application the tag is on the bottom of the burner section. I had to use my camera phone to get the model number on the 80% 3 ton Tempstar that I serviced...

The model number will allow us to view the manual.
 
  #9  
Old 11-26-12, 03:55 PM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
OK, I'll look again.

Meanwhile... I just tried cleaning the flame sensor with some emery cloth... and I snapped off the HSI Grrrr
 
  #10  
Old 11-26-12, 04:26 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,568
Received 50 Likes on 46 Posts
That thing looks like it will break with a strong wind.
The valve has problems with poor solder connections.
 
  #11  
Old 11-26-12, 09:42 PM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Alright, I got a replacement flame sensor and HSI.... didn't solve anything, but at least that's been ruled out.

T8MPN100F14A1 is the furnace model number. Any thoughts would be appreciated. Its cold

I've got an HVAC guy now but he can't come until Friday and he said his best guess is the flame sensor.
 
  #12  
Old 11-26-12, 09:53 PM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,244
Likes: 0
Received 4 Likes on 4 Posts
it is likely the (dumb) smart valve. (gas valve)
 
  #13  
Old 11-26-12, 10:17 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,568
Received 50 Likes on 46 Posts
  #14  
Old 11-26-12, 10:48 PM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Great... another expensive part that I don't know if it'll solve it or not.

Supposedly this furnace has a 10 year "limited" parts warranty, but only if it was registered in a "timely manner" and I'm not the original owner, so I doubt I'll get anywhere there.

Maybe I'll try to service that "no serviceable parts" valve. If it catches on fire... well, that's what insurance is for (yes, I jest).


The pc board is the next cheapest thing to replace. You guys think I should jump straight to the "smart" valve then?

Am I better off just getting a new furnace?
 
  #15  
Old 11-26-12, 10:55 PM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Thank you for that document though! My experience exactly mirrors that described under the heading: "Heating Request with Gas Supply Line Shut Off"

So, why is the gas supply line shut off?
 
  #16  
Old 11-27-12, 06:18 AM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,568
Received 50 Likes on 46 Posts
If you replace the furnace avoid anything with a Honeywell smart valve.
 
  #17  
Old 11-28-12, 03:27 PM
S
Member
Thread Starter
Join Date: Nov 2012
Location: Canada
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
It appears it was the "Smart Valve" that was faulty. Replaced it and it now works fine. However, I've read other posts on the net where people replaced it and it worked fine for a short while... so I guess we'll see.

Stupid that it throws a specific code pointing to something else when it itself is faulty.
 
  #18  
Old 12-01-12, 01:44 PM
Houston204's Avatar
Forum Topic Moderator
Join Date: Oct 2009
Location: Texas
Posts: 7,568
Received 50 Likes on 46 Posts
The smart valve isn't as easy to check as a standard valve with a separate control board.
Color diagrams help.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: