# York furnace inducer motor won't shut off



## yuri (Nov 29, 2008)

Once the thermostat/tstat is satisfied ( house is warm enough ) then the burner shuts off and most brands run the inducer for another 30 seconds to purge any fumes out ( post purge ).

After that it shuts off and the main air fan ( blower ) runs for another 2-3 mins depending on what it is set for on the circuit board.

If the inducer fan keeps running then it usually is the relay for it on the circuit board is sticking ON.

Remove the fan door and press in the door switch and keep it ON with duct tape.

Start and run the furnace and get the burner and blower running. Then get a helper to drop the tstat to below the house temp and everything should shut off in the proper sequence.

If the inducer keeps running then carefully tap the 1" square black plastic relays on the circuit board with the back end of a plastic handled screwdriver.

If it stops then you know one is sticking and you need a new circuit board.


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## user_12345a (Nov 23, 2014)

You can also use a wire with alligator clips and jump R to W with the thermostat in the off position, rule out the stat completely.


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## biglars57 (May 8, 2018)

Thanks for the quick response Yuri! I am out of town and won't be back with the furnace until this weekend and I'll try what you have recommended. But I will add that the furnace shuts down after about the same amount of time regardless of what temp has been reached. And the Nest unit that we use is orange (calling for heat) but furnace will not restart until the power switch is turned off then on again. Would the relay or board cause the early shut down too?


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## yuri (Nov 29, 2008)

Nest has had LOTS of problems.

Do you have it hooked to a C wire in the furnace?

Some Nests may use a power stealing feature and that can fool the circuit board into thinking it is slightly calling for heat with a low voltage signal. That can barely trigger the inducer fan relay.

This sounds complex and it is for a layman. Power stealing thermostats and ones that use a cheater device called a fast stat can trigger inducer relays and damage circuit boards.

You could try remove all the thermosat wires after labelling them. Then jumper R to W and press in the door switch and tape it closed with duct tape. Run the furnace until the main blower starts and then remove the jumper carefully while the burner is on.

If it shuts down properly and the inducer is off then it may be the Nest. You should have a dedicated wire to the Nest from the furnace.

Honeywell and Ecobee are better units IMO.


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## biglars57 (May 8, 2018)

I installed the Nest thermostat myself and yes it has 5 wire supply with a blue common wire supplying continuous 24v power to the thermostat, which I confirmed with my voltmeter. I'll try connecting the R to the W to see if the Nest is the problem....but I kind of doubt that it is. 

I've read where inducer fans can stick on, with the furnace continuing to cycle on and off as heat was needed....which sounds like the stuck relay. With mine it seems like something is shutting the furnace off and locking the unit down until an on/off re-set is done before the furnace can be re-ignited. I never did try turning the thermostat down prior to the furnace shutting itself off to see if the inducer fan would shut down/cycle properly. 

Given the cost of a control board is about the same as another repair visit (without parts) maybe it might be worth changing the board out to see if that fixes things?


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## yuri (Nov 29, 2008)

The inducer creates a draft which closes a pressure switch to prove there is safe draft for combustion.

Once the burner shuts off the switch must open or the board won't allow it to restart the burner. It checks for a open pressure switch as part of the startup routine.

I suspect your board is bad and BTW my 10 yr old Lennox G51 had a bad inducer relay/

Would not stay closed. 10 yrs is the average life of some boards. Kinda ironic?

Try supplyhouse.com or americanhvacprts.com

Some boards are not too expensive so I would DIY.


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## ClimateCreator (Nov 30, 2017)

Some units run the inducer like that after a fault has been detected to get your attention, it's not "stuck" on. The idea is you'll hear it then investigate to see what the flash code is on the blinking light and have an idea why it's locking out.


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## biglars57 (May 8, 2018)

ClimateCreator said:


> Some units run the inducer like that after a fault has been detected to get your attention, it's not "stuck" on. The idea is you'll hear it then investigate to see what the flash code is on the blinking light and have an idea why it's locking out.


If that is the case with mine it would explain what's happening. My York model # is PV9C20N100UP11B


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## yuri (Nov 29, 2008)

If it is another fault then you need to find out what it is.

Intermittent ones are the worst.

I have had to stop/start units 24X in a row to catch them. If you have the patience then remove the thermostat wires and get yourself a jumper wire with alligator clips. Radio Shack has them.

Then stop/start the unit by jumpering R to W and usually you can catch it in 24 tries. The logic is if a furnace runs every half hour where I am and fails once a day you can catch it failing in action and see the error code. Most techs don't have the patience or try this method.


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## biglars57 (May 8, 2018)

Well as an update.....this past weekend we had a cold front move through and the furnace worked flawlessly. I made a point of starting and stopping the furnace numerous times and it started up and shut down just like it should. I guess I'll just keep testing it when I can over the summer and see if the problem comes back. At this point I'm planning to replace the board if the problem resurfaces and go from there. Given the technician couldn't solve things when it was acting up, I'm thinking this will resurface at some point. 

Thanks for the help.


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## yuri (Nov 29, 2008)

Yeah they don't fix themselves and the problem will get more frequent.


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## biglars57 (May 8, 2018)

Well with fall and cold temps our furnace acted up again and I replaced the control board. I didn't check what errors were blinking before but after the new board went in I got a 4 blink limit switch open error and furnace would not fire and blowers would run a while and then shut off. I checked continuity on all limits (Main, Inducer, and roll out) and all had continuity. I did notice that when the error was blinking and I started the furnace, the inducer started right away as usual...but the main blower would turn on earlier than it does when the furnace was lighting and functioning properly.


The problem seems to be intermittent as yesterday morning it did not fire up and this morning it did. As the limit error was happening with the unit cold I thought one of the limits might be bad so I jumped the main and the roll out and no change. I did not jump the inducer but it did have continuity. Is it possible that the harness is not making good contact with the board???


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## user_12345a (Nov 23, 2014)

Check the schematic, you can ohm out the whole circuit with limits (connections disconnected from board), maybe there's a bad connection somewhere and vibration is affecting it.

You can also check live, checking voltage relative to transformer common at different points to see where your break is. The circuit is open between the last point you see voltage and the point you start seeing 0v.

Can do it with the blower access panel open but door switch depressed, one meter lead on the C terminal. Or if the furnace cabinet is grounded to transformer common, you can contact one meter lead to the cabinet while testing different points.


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## slwtypmark (May 17, 2018)

Did you check for an Auxiliary Limit Switch ?..usually mounted on or near the Blower housing.


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## beenthere (Oct 11, 2008)

That should be a 2 stage furnace with a VS blower.


As suggested earlier, jump from R to W1 and see if it runs properly. Also, make sure the blue wire is connected to C in the furnace, and not to W2.


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## biglars57 (May 8, 2018)

Thanks for the advice! I work out of town so unfortunately I won't get back to the furnace until Friday. I had my wife send me a picture of the wiring diagram and it shows the three limit switches in series on a single circuit with the low pressure switch branching off with a separate wire returning to the control board. When I tested things last weekend I jumped out the main limit LS1 and the rollout ROSI and the error didn't clear. At this point I'm thinking it's either a bad inducer limit switch LS2 or a break in the circuit. As I now know the wiring layout I can check for voltage at all points to determine where the problem is.



As I've replaced the board I now have ordered and plan to replace the 3 limits and the 2 pressure switches. The board was only $150 and the switches were under $100. When I was checking things out last weekend I exercised the pressure switches and noticed continuity improved after the clicked a few times so I figured given the age of the furnace it wouldn't hurt to replace the safety switches at about the same cost as a tech visit with no parts.


I also ordered a digital differential pressure gauge to measure the pressure drop from the inducer to the burning box. I want to make sure I got the proper differential and airflow. I'll update after I get back to the unit this weekend. 



Thanks again for the help!!


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## biglars57 (May 8, 2018)

beenthere said:


> That should be a 2 stage furnace with a VS blower.
> 
> 
> As suggested earlier, jump from R to W1 and see if it runs properly. Also, make sure the blue wire is connected to C in the furnace, and not to W2.



I wired the nest thermostat myself and the blue is connected to the common. I will also try jumping the R to W1. Thanks


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## user_12345a (Nov 23, 2014)

Don't change out any parts before identifying where the break in the circuit is with your meter. There's no need to do so, don't waste your money.


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## biglars57 (May 8, 2018)

user_12345a said:


> Don't change out any parts before identifying where the break in the circuit is with your meter. There's no need to do so, don't waste your money.



I hear ya......but given I'm gone during the week I want to make sure I get it fixed. Last weekend after installing the board things seemed to be fine but come Monday morning they weren't. I'm concerned I'll get home and the furnace will work fine until I leave again. So for me it's just insurance to replace all the switches.


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## user_12345a (Nov 23, 2014)

The problem may not be in the switches, could be a connection.

For the high limit to stick open, it has to open at least once, and it shouldn't ever be tripping.

The rollouts are usually manual reset so if one trips the furnace won't operate without resetting it.


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## biglars57 (May 8, 2018)

Got back into town late last night and 4 blink limit switch error showed when I started the furnace. As I didn't have much energy I decided to just switch out the limit switch on the inducer I thought might be bad, figuring I'd dive into the complete diagnostics today. Once switch was in everything fired up and ran perfectly all night. The defective switch I pulled out still had the plastic shield it comes with attached which I know needs to be removed. I'm certain the factory wouldn't send the switch out that way so I'm guessing my furnace guy might have switched it out back when we had problems with the exhaust icing up. I've got a sneaky suspicion that he wanted to sell me a new furnace this time around, as I think the switch was the problem last spring too. 



I'd like to clean things up the best I can....I see a removable steel plate on the front of the furnace above the burning chamber. If I wanted to clean the heat exchange areas is this to be removed. And is this something I can do myself?


Thanks again for all the advice!!!


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## biglars57 (May 8, 2018)

I read on another forum where the author replaced his limit switch and left the protective cover on and someone told him it should come off to expose the switch. As the switch I replaced came off with the cover attached I'd just like to confirm that it is intended to be removed?? I've attached a picture of the old switch with old and new cover.


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## supers05 (May 23, 2015)

I've never seen one come with a protective cover from any of my suppliers. 

Edit: I've checked the York portal. It looks like the inducer limit. (S1-02538737000) That one REQUIRES the cover to protect it from acidic flue condensate. This is NOT a cover for shipping. 


Cheers!


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## biglars57 (May 8, 2018)

supers05 said:


> I've never seen one come with a protective cover from any of my suppliers.
> 
> Edit: I've checked the York portal. It looks like the inducer limit. (S1-02538737000) That one REQUIRES the cover to protect it from acidic flue condensate. This is NOT a cover for shipping.
> 
> ...



Put the cover back on and it did fit in snug, so I can see where it is meant to seal/protect the metal on the switch.


Thanks for taking the time to look that up:thumbup1:


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