# Tempstar pilot not lighting after draft inducer replacement



## Kdavid (Mar 26, 2009)

Hello,

furnace: Tempstar NUG9075FGB1 about 13 years old
smart valve: SV9500M 2674

The draft inducer broke so I ordered a new one. The furnace has been off for four days as I was waiting for the new draft inducer to come in and install it. 

So I installed it...










I go through the sequence of turning the furnace back on and the pilot won't light. The draft inducer starts, but that's where it ends. No spark or glowing from the igniter. 

So I take the cover off to the pilot chamber...










When I start the furnace I can hear the pilot gas coming out after the draft inducer starts. So when I light the pilot manually and put the cover on quickly the flame goes out as if there was too much of a draft or not enough oxygen.:wink:

So my question is...is the igniter supposed to glow to keep the flame going or does it just spark to light it once? If it's supposed to be glowing then that's my problem, but either way I don't see it spark or glow. I'm going to test it with an ohm meter when I get home. 

So the furnace has been off for four days and all of a sudden something else is broken...what the hell. :thumbsup:

Thanks for your time,
Dave


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## kenmac (Feb 26, 2009)

The ignitor glows & lights the pilot... I see you have a smart valve Try cleaning the pilot orifice if everything else works


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## Kdavid (Mar 26, 2009)

kenmac said:


> The ignitor glows & lights the pilot... I see you have a smart valve Try cleaning the pilot orifice if everything else works


Thanks for the reply. Yes I hear the smart valves are actually called dumb valves. I can hear the gas coming out of the pilot pretty good so I think it's ok, but i will clean it.

There is never any sparking or glowing, that i can see, from the igniter.


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## kenmac (Feb 26, 2009)

........ You should check ignitor Or the connections


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## beenthere (Oct 11, 2008)

You disturbed the dumb valve when you changed the inducer.
Dumb valves don't like to be disturbed.

It messes up the wire connections, in the molex plug/connector.

Reseat them.

Maybe your dumb valve will forgive you. Some do, some don't.


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## Kdavid (Mar 26, 2009)

I tried reseating the connector to no avail.

I did some measurements...

I get 13 Ohms across the igniter (blue wires) so it seems shorted. There is also 0 Volts to the igniter. 

I heard the igniter should be around 80 Ohms so it leads me to believe the igniter is bad. The replacement part number is Q3400A 1024. 

If indeed the igniter should be low resistance then the valve is not giving voltage. Should be 24v correct?


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## hvaclover (Oct 2, 2008)

The ignitor should not be over ten ohms..

There is 24 present but its hard to get meter probes into it for a good read.

If you hear gas than your valve is getting power.

Change the igniter.


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## Kdavid (Mar 26, 2009)

hvaclover said:


> The ignitor should not be over ten ohms..
> 
> There is 24 present but its hard to get meter probes into it for a good read.
> 
> ...


Thanks for the reply.

I meant the igniter is not getting 24V it's actually getting 0V. Maybe the valve is not switching the 24V to the igniter?


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## hvaclover (Oct 2, 2008)

You said you heard gas and lit the pilot by hand that means the valve is passing gas to be lit by the igniter. There is 24 V available if this happens.

Granted, the valve could be operating intermittently, but the igniter would have heated up in the scenario described above. 

Possible to have bad valve and igniter? Yeah, but doubtful. You are doing something wrong.


Your furnace has been out for four days; what are you doing for heat?


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## Kdavid (Mar 26, 2009)

Yes yes I agree that there is 24V to the valve, but the igniter is seeing 0V at all times. I hear some people wedge something between the molex connector to the igniter, but in my case wiggling or reseating the connector does not help. Shouldn't the ignitor see some voltage even if its resistance is higher now? 

No heat at all...the house has been a constant 50 degrees...waking up in the morning sucks.


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## hvaclover (Oct 2, 2008)

Kdavid said:


> Yes yes I agree that there is 24V to the valve, but the igniter is seeing 0V at all times. I hear some people wedge something between the molex connector to the igniter, but in my case wiggling or reseating the connector does not help. Shouldn't the ignitor see some voltage even if its resistance is higher now?
> 
> No heat at all...the house has been a constant 50 degrees...waking up in the morning sucks.


You have no heat for four Days? And it's fifty degrees.

Get a new vlave and igniter. The resistance it too high for the igniter. It won't last much longer.


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## hvaclover (Oct 2, 2008)

here's a link to help you http://www.fwwebb.com/pdf/htgcat03/2003htgcat_p207-208.pdf

From Honeywell:

AA. - The resistance of a Norton silicon igniter used in the Q3450 or Q 3480 pilot assemblies, when new and cold, will be between 3 and 4 Ohms (average 3.7 Ohms) as the igniter ages the resistance will increase. _*When its resistance reaches 10 Ohms the igniter should be replaced *_


You have 13 ohms.


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## Kdavid (Mar 26, 2009)

Thank you for that link...I actually just got off the phone with FW Webb and they have the igniter in stock...will have to get it tomorrow.

Ok so it seems I need a new valve as per the troubleshooting instructions (no voltage at HSI element output). Thanks for the info man.


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## hvaclover (Oct 2, 2008)

Like I said, get 'em both.


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## Kdavid (Mar 26, 2009)

Oh man this troubleshooting is going to go forever haha. 

I just checked the control harness voltages and here's the new deal...

24v common to 24v hot = 29V

24v common to 24v thermostat or pressure switch = 0V

So that looks like the problem. 

The pressure switch is functioning ok since it closes when the inducer goes on. When the switch is closed I read 29V across it.


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## hvaclover (Oct 2, 2008)

You would not get gas at the pilot as you earlier stated were that true.


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## hvaclover (Oct 2, 2008)

Might be time to call a pro.

You an engineer by any chance?


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## kenmac (Feb 26, 2009)

sounds like it's the ignitor or the electrical portion that feeds power to the ignitor..Like hvclover said .If it were the vaccum/pressure switch you wouldn't have gotten pilot gas.....I hate those dumb valves..Over the years honeywell has made several changes to the valve ..It's still dumb


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## qbert (Mar 23, 2009)

The pressure switch is functioning ok since it closes when the inducer goes on. When the switch is closed I read 29V across it. When a switch is closed you should not read source voltage


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## kenmac (Feb 26, 2009)

You don't read voltage across a closed switch. You read voltage across an open switch. If it's closed you can read from switch to ground


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## beenthere (Oct 11, 2008)

kenmac said:


> You don't read voltage across a closed switch. You read voltage across an open switch. If it's closed you can read from switch to ground


That seems to confuse a lot of techs also.


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## Kdavid (Mar 26, 2009)

hvaclover said:


> You an engineer by any chance?


I am and the electronics involved in this is kindergarten stuff. 

Alright so this is also confusing me...when the switch is closed I get continuity across it and also a 29v drop across it. :wink: Bad switch...I don't get it? Please someone confirm if this is a crazy switch.


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## hvaclover (Oct 2, 2008)

Kdavid said:


> I am and the electronics involved in this is kindergarten stuff.
> 
> Alright so this is also confusing me...when the switch is closed I get continuity across it and also a 29v drop across it. :wink: Bad switch...I don't get it? Please someone confirm if this is a crazy switch.


First law of electricity I learned was voltage takes the least line of resistance. In this case the closed switch is that line of least resistance, your meter the higher path. Can't have both.


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## Kdavid (Mar 26, 2009)

Cool...I got it. 

When I pull the wires off the switch it reads open with the induction motor on and read open with the motor off. Is it supposed to do that?


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## kenmac (Feb 26, 2009)

Kdavid said:


> I am and the electronics involved in this is kindergarten stuff.
> 
> Alright so this is also confusing me...when the switch is closed I get continuity across it and also a 29v drop across it. :wink: Bad switch...I don't get it? Please someone confirm if this is a crazy switch.


 


How can you be confused ??....'' this is kindergarten stuff " :whistling2:


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## hvaclover (Oct 2, 2008)

Kdavid said:


> Cool...I got it.
> 
> When I pull the wires off the switch it reads open with the induction motor on and read open with the motor off. Is it supposed to do that?



You said this was kindergarten stuff.

I am beginning to think you are deliberately posting misleading info. The inducer would have to be running to check continuity and you did not say that the wire were disconnected. You would have blown the fuse in your meter checking that system live.

Five days no heat.

I am beginning to smell a troll.


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## kenmac (Feb 26, 2009)

hvaclover said:


> You said this was kindergarten stuff.


 


Must have flunked !:yes:


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## Kdavid (Mar 26, 2009)

It's true no heat since Sunday. The house never got below 49 and I travel a lot so hasn't been a big deal. It's supposed to be 63 today and that is good news. It actually feels colder inside and outside. 

Gents, I deal with high speed surface mount electronics hence my kindergarten comment. I still appreciate your help. The only reason I didn't call a pro is because I can get all these parts on Ebay for 1/10th of what a pro would charge me and I could go without heat for a while. 

So please help me out man. 

I checked the pressure switch with its wires plugged in and not plugged in.

With the wires plugged in:
The switch closes when the induction motor turns on and is open when the induction motor is off.

With wires pulled out:
The pressure switch is open all the time.


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## hvaclover (Oct 2, 2008)

kenmac said:


> Must have flunked !:yes:


Ken you know how some pros come here as impostors just to stir up crap
and then crow about it on what ever pro site they come from.

This gent has all the ear marks of a troll. You don't goof up that many readings ...


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## Kdavid (Mar 26, 2009)

hvaclover said:


> Ken you know how some pros come here as impostors just to stir up crap
> and then crow about it on what ever pro site they come from.
> 
> This gent has all the ear marks of a troll. You don't goof up that many readings ...


Haha you got me!!!! I love the word goof.

What have I goofed up?


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## hvaclover (Oct 2, 2008)

Kdavid said:


> It's true no heat since Sunday. The house never got below 49 and I travel a lot so hasn't been a big deal. It's supposed to be 63 today and that is good news. It actually feels colder inside and outside.
> 
> Gents, I deal with high speed surface mount electronics hence my kindergarten comment. I still appreciate your help. The only reason I didn't call a pro is because I can get all these parts on Ebay for 1/10th of what a pro would charge me.
> 
> ...


With all due respect I am bowing out of this thread because either one; the guy is tring to prank us. Or two, he does not follow instruction and second guesses the answers given.


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## kenmac (Feb 26, 2009)

Kdavid said:


> With the wires plugged in:
> The switch closes when the induction motor turns on and is open when the induction motor is off.
> 
> With wires pulled out:
> The pressure switch is open all the time.


 
Then,
Must be an electronic pressure switch


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## beenthere (Oct 11, 2008)

Kdavid said:


> Gents, I deal with high speed surface mount electronics hence my kindergarten comment. I still appreciate your help. The only reason I didn't call a pro is because I can get all these parts on Ebay for 1/10th of what a pro would charge me and I could go without heat for a while.


Ebay, thats where I get all my high speed eletronics stuff.

And my electronics books.

Those dang electronic engineers, want to much to design things.


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## hvaclover (Oct 2, 2008)

kenmac said:


> Then,
> Must be an electronic pressure switch


Nope. there's a pic of the switch. Regular old diaphragm switch, not a transducer.

You can see it in the pics


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## Kdavid (Mar 26, 2009)

hvaclover said:


> With all due respect I am bowing out of this thread because either one; the guy is tring to prank us. Or two, he does not follow instruction and second guesses the answers given.


With all due respect I agree I need a new igniter, but the valve seems to be fine per the troubleshooting instructions you supplied. All eyes are on the pressure switch as ken mentioned no?

I do agree I have to upgrade to the sv9501 because of the better design, but at the moment I would love for the heat to go on.

Shorting the switch should be a good test correct?


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## Kdavid (Mar 26, 2009)

hvaclover said:


> Nope. there's a pic of the switch. Regular old diaphragm switch, not a transducer.
> 
> You can see it in the pics


So you think it's still the valve?


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## kenmac (Feb 26, 2009)

hvaclover said:


> Nope. there's a pic of the switch. Regular old diaphragm switch, not a transducer.
> 
> You can see it in the pics


 

Just joking :laughing: Like the westinghouse joke


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## Kdavid (Mar 26, 2009)

Bam!!!!!!!!!!!!!!! well what do you know....I stay home because of a world record hangover and I fix my furnace. It's a beautiful day after all. :thumbup:

I shorted the switch and we have heat!!!!

... and you wouldn't believe I just bought a new switch for $8 on ebay...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120326620243

Thanks so much guys. Hugs and kisses.


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## kenmac (Feb 26, 2009)

qbert said:


> The pressure switch is functioning ok since it closes when the inducer goes on. When the switch is closed I read 29V across it. When a switch is closed you should not read source voltage


 

This statment told you the switch was bad


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## hvaclover (Oct 2, 2008)

I still think he is a troll..knew too much about the system to make those screw ups. misreading the voltage at the valve.

E


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## hvaclover (Oct 2, 2008)

Kdavid said:


> Bam!!!!!!!!!!!!!!! well what do you know....I stay home because of a world record hangover and I fix my furnace. It's a beautiful day after all. :thumbup:
> 
> I shorted the switch and we have heat!!!!
> 
> ...



And to think, it only took five days.

My kid is an EE and a damn good one, so I KNOW you were BSing us all the thruway this post or you were drunk.

Nice combo --a drunk engineer and a gas furnace.

You are cutting out because you were found out, not because you fixed it.


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## Kdavid (Mar 26, 2009)

hvaclover said:


> ..knew too much about the system


I will take that as a compliment. Check out my new signature!!!

I will admit I may have been inebriated a few times when posting. 

A switch in theory is not supposed to read a voltage across it when closed....I know this, but at the same time it was confusing the hell out of me. See...if I had experience like you guys I would've shorted the switch four days ago. 

It is true that you learn more on the job than in school.

Cheers....opens a beer.


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## hvaclover (Oct 2, 2008)

Kdavid said:


> I will take that as a compliment. Check out my new signature!!!
> 
> I will admit I may have been inebriated a few times when posting.
> 
> ...


I can recommend a good 12 step program 'ya lush.


A drunk hvac tech burned down my mother's home with her still in it.


I won't tolerate idiots working with gas while under the influence.

Check into a Canadian 12 step program before you kill somebody.


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## hvaclover (Oct 2, 2008)

My user name is Copyrighted. Use at your own risk


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## beenthere (Oct 11, 2008)

The pressure switch is a safety device.

Buy passing it, doesn't mean its the problem.

It may have been doing its job. 

If you install a new switch and it doesn't work. Your right back at step step 2.


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## kenmac (Feb 26, 2009)

beenthere said:


> The pressure switch is a safety device.
> 
> Buy passing it, doesn't mean its the problem.
> 
> ...


 

If he would have put a small amount of vaccum on the hose & checked or checked vaccum on the vent motor ... He would know......He is a EE you know


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## hvaclover (Oct 2, 2008)

beenthere said:


> The pressure switch is a safety device.
> 
> Buy passing it, doesn't mean its the problem.
> 
> ...


Hey Been he replaced the inducer. 

Assuming he isn't messing around he missed a major component that was supposed to go with the inducer.

I'll PM you the info. Only us old ICP dealers are up on the part concerned.


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## Kdavid (Mar 26, 2009)

hvaclover said:


> I can recommend a good 12 step program 'ya lush.
> 
> 
> A drunk hvac tech burned down my mother's home with her still in it.
> ...


You seem like a good person hvaclover, someone that cares, as I have noticed here. You took time out of your day to help a fellow human in need and I greatly appreciate your help and everyone that chimed in. If you felt disrespected by any of my posts than I apologize for that. Due to your lack of knowledge about me I will also brush off the insult to my intelligence as I have nothing to prove to you. My work in the business world speaks for itself...it saves lives. 



beenthere said:


> The pressure switch is a safety device.
> 
> Buy passing it, doesn't mean its the problem.
> 
> ...


You sir are a gentleman and a scholar. Very good info...thanks for posting.


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## Kdavid (Mar 26, 2009)

hvaclover said:


> Hey Been he replaced the inducer.
> 
> Assuming he isn't messing around he missed a major component that was supposed to go with the inducer.
> 
> I'll PM you the info. Only us old ICP dealers are up on the part concerned.


Care to share that info? I mean why would you withhold something like this? :thumbdown:

Are your referring to the blower restrictor or the o-ring?


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## hvaclover (Oct 2, 2008)

hvaclover said:


> My user name is Copyrighted. Use at your own risk





Kdavid said:


> You seem like a good person hvaclover, someone that cares, as I have noticed here. You took time out of your day to help a fellow human in need and I greatly appreciate your help and everyone that chimed in. If you felt disrespected by any of my posts than I apologize for that. Due to your lack of knowledge about me I will also brush off the insult to my intelligence as I have nothing to prove to you. My work in the business world speaks for itself...it saves lives.
> 
> 
> 
> You sir are a gentleman and a scholar. Very good info...thanks for posting.



You just ain't hit the right button for Been to set you straight.

He gets gets compliments all day which are well deserved.

You just happen to it my button and you got what you deserved. 

Where i live had I made a house call to your residence and found you blotto and messing with a gas appliance I would have had you arrested
for reckless endangerment to life and property.


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## hvaclover (Oct 2, 2008)

Yep a troll alright.


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## hvaclover (Oct 2, 2008)

Kdavid said:


> Care to share that info? I mean why would you withhold something like this? :thumbdown:
> 
> Are your referring to the blower restrictor or the o-ring?


No but the mods have been notified.:thumbsup:


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## Kdavid (Mar 26, 2009)

hvaclover said:


> You just ain't hit the right button for Been to set you straight.
> 
> He gets gets compliments all day which are well deserved.
> 
> ...


Take it easy. Like I said when I was using the computer sure I might have had a beer or two, but nowhere did I say I was working on the furnace and drinking.

Once I posted the problem in my system it seems you have been doing nothing but harping on an irrelevant issue. If calling me and idiot makes you feel better then by all means continue.

After all you were the one who said it's not the switch...



hvaclover said:


> Nope. there's a pic of the switch. Regular old diaphragm switch, not a transducer.
> 
> You can see it in the pics



Again...thanks to all who helped including you hvaclover. I learned a lot and will not forget this experience.


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## kenmac (Feb 26, 2009)

That's not what he meant by that statment


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