Question for all you Hvac guys or anyone else who knows about furnaces

[kamby]

Heres the scoop.

I have a Bryant plus 80 furnace that intermitantly works. Sometimes it will fire up just fine other times it will do its 3 attempts then give a 3 hour lockout code and another code. 14 and 34 are the codes. A/C end of it works great.

Furnace is an older unit installed in 1998, it has A/C and an electric air cleaner.

Any ideas what to try or to do.

Also at the same time the gas fireplace of the same year and install day wont keep its pilot light lit. Both are of the same gas line. The water heater at the other end of the home has no problems at all. Most the time the pilot light only last 5-15 min then it goes out. Once it stayed on 1/2 a day.

Im hoping to make it through the winter with what i have before repacing the units next spring/summer

Thanks

Jason

 

[Georgesalmon]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

Thermocouple sounds bad. Little thing that touches the pilot flame and sends a signal to the gas valve to stay on. If it doesn't get hot it tells the gas valve to shut off so no extra gas gets in the house thats not being burnt. That's for the fireplace, could also be the same problem for the furnace if it also has a pilot light. That one could be several other things as well. I'm not smart enough to help you with that.

 

[colbyt]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

There should be a label inside the unit that explains the codes as well as a flow chart indicating the boot sequence.

Fireplace = bad or loose thermocouple or possible lint in the pilot assembly which reduces flame size and trips the thermocouple off. Try a fine wire brush to the pilot assembly first; a buildup of powdered ash can do the same thing.

 

[kamby]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

Thanks for the replies i will try that on fireplace makes sense cause i cleaned a lot of white ash out of it when i cleaned the glass. Had the problem before i cleaned the unit.

The furnace doesnt use a pilot. From what i can see quickly is the vent fan turns on. The red light glows then nothing. The glowing will repeat until it either fires or cycles three times. After the glowing there is a clicking noise either a sparker or gas valve?. I will double check the fire order when i get home from work and can poke at it longer.

 

[Georgesalmon]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

Winter before last had a problem that sounds similiar. It was my ignighter(sp). Anyway I wasn't smart enough to fix it myself, had to call repairman and cost me $125 parts and labor which i didn't think was to bad considering the guy came out at 10pm. It was getting pretty cold up here in WI that night. Probably would have been cheaper if I wasn't so darn stubborn thinking I could fix it myself. Boss made me call, she was cold.

 

[colbyt]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

If it was the ignighter I don't think it would ever fire; once they crack there is no circuit. BTW if you ever change one do not touch the ceramic portion with your naked hand. The hot spot from the oil on your skin may cause premature failure. I learned that one the hard way. They cost about $30 at the supply house; 65-75 off the truck and a service call. A nut driver and nerve is all you need after you turn off the power.

For the OP's intermittent problem I suspect a flaky draft fan or a failing control board. Sadly you can buy a nice quad core mainboard for what those silly little control board sell for.

 

[CharlieB]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

Check these threads

http://www.diychatroom.com/f17/bryant-80-gas-furnace-wont-light-34116/

http://www.askmehelpdesk.com/heatin...0-gas-furnace-wont-ignite-burners-415910.html

 

[sublauxation]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

I've got the same furnace installed in 2002 and mine did roughly the same thing. Our problem was that the module on the blower motor died. It's actually just a thermister (looks like a lollipop) that gets shorted out in the module. It's a very common/the most common problem with that furnace. The whole part can be found online for about $260 but the repair guys want about $350 plus labor. The thermister is about $2.00 and can be soddered in. The repair guy ran a jumper wire across ours and I keep meaning to replace it but it works just fine as is. Testing that would be a pretty good first bet as there are only 3 bolts that hold it on. I suppose you could wiggle it around while checking resistance or jump it and put it back on/see if it works continuously. I actually have the part number for the thermister written down somewhere, I'll try finding it. They also commonly have problems with the main circuit board which may actually be cheaper than the fan module. The repair guy told me his next step would be to take that off and check the back side for burnt spots.

 

[hrdwrkingacguy]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

More then likely the hot surface ignitor is bad...They have a resistance value to them in a cold state and another one in the hot state...When they go bad, they don't have to much resistance to close a current sensing relay in the board to move on to open the main valve...Basically the board needs to see the hot surface ignitor has done its thing before it lets the gas valve energize...Typically < 70 ohms is what we look for, but there are many different ones...I would start with that, they are like 30$ at a parts house...I would get the OEM one from Bryant/Carrier...

BTW if any safeties were open you wouldn't get to the point were the hot surface ignitor starts...You would get a flash code on a call for heat with a roll out switch, High limit, induction fan proving switch...I would start with the Hot surface ignitor, then the board...

I need a m# and s# to tell you what the flash code means....

 

[sublauxation]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

As I think about it mine did go out on high limit. Keep that thermistor in mind though if you have that problem in the future, I was told it was surprising mine made it this long. Good luck with the cure and hope it's easy, some of those control boards and pieces are unbelievably spendy. When I first started trouble shooting and looking at prices of parts I prepared myself to buy a new furnace.

 

[hrdwrkingacguy]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

I would doubt its the board...The HSI heats and cools thousands of times in its lifetime...They go bad...The more resistance they have the less current the current sensing relay sees and it won't prove that its working...two wires and 30$ should fix it...

The module and HSI are < 140.00$ my cost...Its fairly plug and play if you actually need that...gas valve is a different story...

 

[rbh]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

This is only a half answer-

My buddy had the same issue, "I think" and his bro inlaw at the time who does HVAC said for him to take a piece of fine emery cloth and clean the carbon build up from the????

Thats were I am lost, so when I talk to him I will ask him the specfics.

 

[Fishing Dude too]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

Had this problem on another brand sounds like the explosion preventer is bad, to check would put a jumper in but needs replaced or furnace could explode.

 

[hrdwrkingacguy]

Re: Question for all you Hvac guys or anyone else who knows about furnaces

Had this problem on another brand sounds like the explosion preventer is bad, to check would put a jumper in but needs replaced or furnace could explode.

You mean roll out switch??? A Roll out switch is a saftey...The HSI won't take off with a saftey open...If you see a glow inside the cabinet, all the safeties have to be closed to get that far...If the HSI glows and the gas valve doesn't open, then either the gas valve coil is open(Testable by putting a meter on the wires, 24v and no fire is bad valve or no gas, 0 volts means HSI or the ignition module is bad)

This is only a half answer-

My buddy had the same issue, "I think" and his bro inlaw at the time who does HVAC said for him to take a piece of fine emery cloth and clean the carbon build up from the????

Thats were I am lost, so when I talk to him I will ask him the specfics.

That is spark ignition...different system...A sparker lights a temporary pilot and the flame rod is in the fire...Through flame rectification the module sends power down the ignition wire and it sees a circuit path through the fire to ground and that tells the module that there is a pilot light...Then the gas valve opens...When the flame rod gets dirty it doesn't prove flame and after three tries locks out...