# blower won't shut off on new gas furnace



## johnny67 (Apr 20, 2009)

I can't figure this out. I have a 2year old gas furnace. The blower won't turn off and I can't find a switch on the furnace like my old one had that can keep the blower always on or off. The only switch is for the lower cover that shuts it off. I am not familiar with this furnace because it is a house that I rent to tenants. I tried an old school t stat and a new digital one with the same results. There are only 2 wires coming from the circuit board right now. The only time it shut off was when I raised the heat and then it turned on again and stayed on. The heat works fine. Is there a switch that I am not seeing on the furnace?


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## Plumber101 (Feb 25, 2009)

How many wire are connected at the thermostat?

Also post brand and model of furnace


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## johnny67 (Apr 20, 2009)

2 wires at the t stat. I am not sure what model it is because I am not at the house but if this helps it is a 80+ AFUE upflow/horizontal furnace with no A/C.


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## Plumber101 (Feb 25, 2009)

Where is the furnace installed? Basement, attic...where?


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## johnny67 (Apr 20, 2009)

It is in the basement.


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## beenthere (Oct 11, 2008)

Probably has a dirty/plugged air filter. And the limit switch tripped when they ran it for heat on a cool night.


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## biggles (Jan 1, 2008)

fan ON limit disc might be closed shut.the FAN during heating cycle is 100% isolated from the stat action or call.the actual heating of the heat exchanger or a time delay on the furnace solid stae board(fan relay) runs fan.it's either that disc or the relay on the board is arced closed...tap the relay on the board with a small screwdriver handle see if it opens.if you have the stat in hand with just the subbase wired looking at it the fan closure to run is in the furnace limiting wiring.when the furnace is called for the HEAT-X gets hot and the supply fan comes ON when the stat is satisfied the gas shuts off and the HEAT-X cools down and that disc should open shutting off the fan.


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## johnny67 (Apr 20, 2009)

The filter was very dirty, I put a new one in now. Is there any other clue you guys can give me to know what to look for when looking for the relay to tap on. I will be at the house tomorrow and I will note the make of the furnace and take a few pics of the electronics board etc.. thanks


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## biggles (Jan 1, 2008)

the relay on a solid state board is about 1" x 1/2" in size even though the stat isn't calling it the contacts might be be swinging open when the control voltage is stopped.


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## johnny67 (Apr 20, 2009)

The furnace is a Nordyne model #FG6RA 072C-12A. I took a picture of the board and I was told by the installer that it is probably due to the clogged filter just like you guys said and that the limit switch needs to be replaced. He said that the part is $25 and he could come down and put it in plus a $100 service call. Is this something a handy guy like me can do. I have experience with electrical work. Or is this something left to a professional? I did tap on a few of the black boxes in the pic but it did not turn the fan off (not sure which one was the relay switch)


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## JohnH1 (Jan 9, 2009)

Its not a open limit. You said the heat started and ran fine. If it was a limit the burners would not run. The only thing I could think of is a bad board.


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## johnny67 (Apr 20, 2009)

thats right. When I turn the heat up the fan will shut off for about 10 seconds then it will kick on again with the heat. Although I am not sure if I have let it run the cycle yet since the days around here have been hot, but I can try that tomorrow.


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## JohnH1 (Jan 9, 2009)

I am also not thrilled with the copper gas line. Gas and copper dont play well together. :no:


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## Plumber101 (Feb 25, 2009)

Check the limits that are on the blue wire. There is one right up front and one that is by the blower. They should be closed circuit. They also had a manual reset. The button in the middle of the connector. Just a thought to see if one has tripped.


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## beenthere (Oct 11, 2008)

JohnH1 said:


> I am also not thrilled with the copper gas line. Gas and copper dont play well together. :no:


Natural gas, and copper are fine together.

Its the acid that some of the companies don't remove that is a problem.
Some areas certify their gas to be acid free.

His may be one of those areas.


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## johnny67 (Apr 20, 2009)

Plumber101 said:


> Check the limits that are on the blue wire. There is one right up front and one that is by the blower. They should be closed circuit. They also had a manual reset. The button in the middle of the connector. Just a thought to see if one has tripped.


 
How do you check the limits of the blue wire? I have not seen the manual reset. Where should I look?


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## rusty baker (Feb 13, 2009)

I thought that was odd. All that's used in my area is copper gas lines.


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## Plumber101 (Feb 25, 2009)

Open the link and look at the limit.

There is a blue tab (Yours may not have the blue) But the tab that sticks up you will push in to reset the limit

http://americanhvacparts.com/Mercha...duct_Code=LIMD1370108&Category_Code=fl-tdl-ro

This is just a hunch....


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## johnny67 (Apr 20, 2009)

where about is this limit located?


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## Plumber101 (Feb 25, 2009)

Follow the BLUE wires, Start at the control board. 

I think there are 2 or 3

One can be seen just in front of the flue pipe


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## JohnH1 (Jan 9, 2009)

beenthere said:


> Natural gas, and copper are fine together.
> 
> Its the acid that some of the companies don't remove that is a problem.
> Some areas certify their gas to be acid free.
> ...


I did not know that. Learned something new Thanks :thumbsup:


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## beenthere (Oct 11, 2008)

No problem.


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## Plumber101 (Feb 25, 2009)

Can you check to see when the blower is running all the time do you get a flash code on the control board?


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## johnny67 (Apr 20, 2009)

I see in the picture 2 blue wires going up to the right hand corner of the furnace and attatching to a switch that looks like the one you had in your link. There looks to be a red tab there, I will try to push it in and reset it tomorrow when I am at the house. Would the other limit switch be behind the lower panel of the furnace?

There is a red light that is lit on the board but it is not flashing any codes that I could tell.


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## Plumber101 (Feb 25, 2009)

No, it looks like it is around the burners.

I went to Nordyne site and was reading the install manual. If none of the limits are tripped then I would replace the supply air limit. Right behind the gas valve. To verify that this limit is bad, disconnect power to the furnace. Remove the two wires off the limit and connect the two ends together, then restore power to the furnace and see if the blower stops running

It says in the manual that if the supply air limit is run longer that 4 minutes with a very restricted return air that it can damage the SAL.

Depending on how dirty the filter was, and it would have to be pretty dirty, this could damage it limit


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## Customerservice (Sep 7, 2009)

*Limit Switch*



johnny67 said:


> I can't figure this out. I have a 2year old gas furnace. The blower won't turn off and I can't find a switch on the furnace like my old one had that can keep the blower always on or off. The only switch is for the lower cover that shuts it off. I am not familiar with this furnace because it is a house that I rent to tenants. I tried an old school t stat and a new digital one with the same results. There are only 2 wires coming from the circuit board right now. The only time it shut off was when I raised the heat and then it turned on again and stayed on. The heat works fine. Is there a switch that I am not seeing on the furnace?


 Call a Qualify Service Tec the Limit Switch is bad!


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## Plumber101 (Feb 25, 2009)

Customerservice said:


> Call a Qualify Service Tec the Limit Switch is bad!


 
Simple to do.

You can buy the part online..

Two screws, two wires...

Too simple


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## johnny67 (Apr 20, 2009)

Okay I will check the 2 limit switches to see if I can push them back in then I will check the Sal switch by the gas valve. Is the SAL the one with the yellow and brown wire going to it?


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## Plumber101 (Feb 25, 2009)

Pic of one












Link to manual

http://www.nordyne.com/literature/7085020.pdf

Link to parts manual

http://www.nordyne.com/literature/7087000.pdf

I think the part number you need is 626418

Link to where you can buy...About $15

http://www.mobilehomerepair.com/NordyneGas.html


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## johnny67 (Apr 20, 2009)

thanks alot for all the great info. this is a great web site for the DIYer


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## Plumber101 (Feb 25, 2009)

Just remember to test the it. I told you how earier. Also you can use an ohm meter and check the SLA to see if it is closed or open. It needs to be closed


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## JohnH1 (Jan 9, 2009)

johnny67 said:


> I can't figure this out. I have a 2year old gas furnace. The blower won't turn off and I can't find a switch on the furnace like my old one had that can keep the blower always on or off. The only switch is for the lower cover that shuts it off. I am not familiar with this furnace because it is a house that I rent to tenants. I tried an old school t stat and a new digital one with the same results. There are only 2 wires coming from the circuit board right now. The only time it shut off was when I raised the heat and then it turned on again and stayed on. *The heat works fine.* Is there a switch that I am not seeing on the furnace?


Am I missing something here? He said the heat worked fine if the limit was bad the heat / burners would not operate.


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## johnny67 (Apr 20, 2009)

I checked the 2 limit switches and tried to push in the button but they seemed to be fine and would not push in. I then took the 2 blue wires off of the SAL and connected them together and the fan would still not turn off. I also let the furnace run through a heating cycle and the fan did not turn off after it got to the set temperature. 

Is there any other test I can do to figure this one out?


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## Flashheatingand (Sep 7, 2009)

Look at the photo on #16. The two blocks on the right, both of those blocks is a relay that will energize the fan. While the unit isn't in heating mode & fan is still running, tap each relay with a screwdriver handle. It sounds as if you have a sticking relay. If the fan quits, it's likely that relay is the culprit, and the board should be changed. If the appliance is only 2 years, it's probably covered under a warranty.

Unit should not go into heat mode if there was an open limit switch.


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## Flashheatingand (Sep 7, 2009)

Hey, on second thought, you should turn the line voltage to the furnace off, then tap on the relays.


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## johnny67 (Apr 20, 2009)

Flashheatingand said:


> Hey, on second thought, you should turn the line voltage to the furnace off, then tap on the relays.


ok I will try that. I did tap on them when the fan was on but I will try with the furnace off. 

I will also dig out my reciept for the furnace and see if I still have a warranty.

would it help if I installed the old style T-stat to eliminate the variable of a malfunctioning digital T-stat?


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## johnny67 (Apr 20, 2009)

Today the I had the original furnace installer to come check it out. He found a jumper wire was installed by my ex tenant to keep the fan on all the time. The good part is I was not charged a service call fee (he has a dedicated customer now). I guess if I had posted a better picture one of you guys would have spotted that extra wire. Thanks for all the help.


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