Furnace question

[Slvrvalk1]

My furnace is in the garage where I park my Valkyrie (now it is Valkyrie related).  The fan stays on after the burner has cooled.  It is an older furnace that has been checked for Carbon Monoxide and it is still safe to continue using.  I can order a new control board online.  My question is whether there are other adjustments that must be made with a new control board other than simply replacing the board?

It looks like all of the connections to the control board are plug-in connections.

Any advice will be greatly appreciated.

Thanks.

Dave

[Jess from VA]

I cannot answer most of your questions.

But I thought all furnace fan blowers stayed on a couple minutes after the burner cuts out, to deliver the heat already in the system to the rooms before shutdown.  All mine have.

[KG]

does it have long burners or short burners like small jet engines.

if it has the long burners look above the burners on the back wall and see if there is a box about 4-6  inches tall and 3 to 4 inches wide. take the cover off and there will be a wheel in the center. as the burners burn they heat a bimetal spring which turns the wheel which has contacts to turn the fan on and off.
It also cuts the burners off if the fan fails to come on and prevents overheating of fire.
it may be sticking and not rotating all the way don't touch the wire terminals and gently turn the wheel and see if it stops

if it has the small jet type burners then follow the wires around the burner chamber they will go to a snap switch then go to the next snap switch. these are thermostats some have a reset in between the wire terminals. you need to see if any are tripped are remove the wires and ohm the ones without a reset. there may also be one on the blower housng also.


it will think its hot and run the fan to cool it off

[t-man403]

My furnace is in the garage where I park my Valkyrie (now it is Valkyrie related).  The fan stays on after the burner has cooled.  It is an older furnace that has been checked for Carbon Monoxide and it is still safe to continue using.  I can order a new control board online.  My question is whether there are other adjustments that must be made with a new control board other than simply replacing the board?

It looks like all of the connections to the control board are plug-in connections.

Any advice will be greatly appreciated.

Thanks.

Dave

I'm an HVAC guy.
Make and model would help. It can't be that old if it has a control board.
Does the fan EVER shut down?
Does the T-Stat have a fan switch that has been left in the on position by accident?
Is the filter real dirty? If so, the burner is shutting down on high limit, which would leave the blower running till it cooled down enough to reactivate the gas valve.

Lastly and most importantly ............ my blower has not been shut off for 32 years, summer or winter. It's better for the motor to run and it gives you a healthier environment in the home.

[t-man403]

does it have long burners or short burners like small jet engines.

if it has the long burners look above the burners on the back wall and see if there is a box about 4-6  inches tall and 3 to 4 inches wide. take the cover off and there will be a wheel in the center. as the burners burn they heat a bimetal spring which turns the wheel which has contacts to turn the fan on and off.
It also cuts the burners off if the fan fails to come on and prevents overheating of fire.
it may be sticking and not rotating all the way don't touch the wire terminals and gently turn the wheel and see if it stops

if it has the small jet type burners then follow the wires around the burner chamber they will go to a snap switch then go to the next snap switch. these are thermostats some have a reset in between the wire terminals. you need to see if any are tripped are remove the wires and ohm the ones without a reset. there may also be one on the blower housng also.


it will think its hot and run the fan to cool it off

If any of these are tripped the burner will not light.

[KG]

it will think its hot and run the fan to cool it off

If any of these are tripped the burner will not light.

Thats what I get for posting when getting home at midnight. yeah the burner will not light and some will run the fan and some won't when it trips

[Slvrvalk1]

Thanks to everyone for the advice.  I think I stumbled on the solution to the problem when I checked some additional wires.  One of the wires to some type of sensor in the chamber above the heating element may be loose or the sensor may be failing because when I checked the wire, the furnace started working properly.

I will spend some more time on that area.  I have a HVAC guy coming on Monday.

Thanks.

Dave

[MarkT]

Not a HVAC guy but I maintain my own forced air furnace.  Anyway, I've found several times bad connections at the heat riser switch (sorry, I'd have to go down to the basement to get the proper term for it).  The plug-in, automotive style connectors, being oxidized and not conducting the low voltage well.  Unplug one at a time, clean the spade connectors well, make sure the wires are properly crimped and if a meter says resistance across the connection, solder on a new connector.  I never trust crimp connections without solder. I was surprised to find this more than once.  This may not be your problem, but it can be now or later.

[Brian]

Thanks to everyone for the advice.  I think I stumbled on the solution to the problem when I checked some additional wires.  One of the wires to some type of sensor in the chamber above the heating element may be loose or the sensor may be failing because when I checked the wire, the furnace started working properly.

I will spend some more time on that area.  I have a HVAC guy coming on Monday.

Thanks.

Dave

I am glad to hear you called a service tech. Sounds like it wil be an easy fix for him. If you can, be there when he comes. You are paying for the service call, ask questions but be mindful of the time.

[Slvrvalk1]

The HVAC guy came and replaced one of the contacts on the limit switch, but that did not take care of the problem.  He had to put in a new fan control board.

Thanks for the advice.

Dave

[t-man403]

So you have an ignition board and a fan board, as in 2 boards?

Not a lot of those around here, but I have seen them .

[Slvrvalk1]

Just one board.  I probably should have said "control board"  The fan relay was bad.  The furnace is a "Payne" that was installed in 1986.  The new board is solid state versus the old board.

Dave

[t-man403]

Ah.

26 years ..........that's good life out of a board.

[Ricky-D]

I've a control broad a lot older than that!

***

[t-man403]

I've a control broad a lot older than that!

***

Yes, there are many boards out there that are older and may last the life of the furnace they're in. But considering how many boards fail in less than 5 years, his did good. Having said that, the electronics on furnaces has improved greatly.

[Bone]

I'm thinking Ricky-D did not misspell board

[t-man403]

I'm thinking Ricky-D did not misspell board

Nice!

I totally missed that!!