# Ruud Silhouette II Furnace Problem



## yuri (Nov 29, 2008)

Remove and clean the flame sensor with fine steel wool or emory paper. Should look like this and sit in front of one of the burners.


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## komobu (Nov 14, 2010)

Yuri;

Thanks so much for taking the time to reply. I cleaned the tip and it is working great. Thanks Again!


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## Gitfiddler (Nov 28, 2011)

*Same problem only different*

I have cleaned the sensor 3 or 4 times and my furnace still won't stay lit. I have the board with 3 lights and the flame light never comes on during start-up. I also cleaned all the burners ad checked most of the connections on the circuit board. Can anyone suggest anything else I can check? Oh yeah, it was working yesterday...
Thanks
Gitfiddler


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## Marty S. (Oct 31, 2009)

Gitfiddler said:


> I have cleaned the sensor 3 or 4 times and my furnace still won't stay lit. I have the board with 3 lights and the flame light never comes on during start-up. I also cleaned all the burners ad checked most of the connections on the circuit board. Can anyone suggest anything else I can check? Oh yeah, it was working yesterday...
> Thanks
> Gitfiddler


 Do you have a multi-meter? Only way to know for sure what's going on is to get a DC microamp reading from the flame sensor and check AC voltage from the sensor wire to ground.


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## Gitfiddler (Nov 28, 2011)

Thanks Marty, I read in another thread where you said that the reading should be 1.8 microamps or over when the flame is on the rod...my question is where do I place the pos. and neg.? Also what should te reading be with no flame?:whistling2:


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## Marty S. (Oct 31, 2009)

The control board sends AC voltage to the flame sensor which jumps through the flame and returns to the board via ground(burners first) as DC voltage. First step would be stick one lead of meter on the spade connected end of the flame sensor and the other to ground. With a call for heat you should have 28-80 volts AC. Actual voltage depends on which control board and I do not know the specific range on yours. If no voltage then the board is bad.

To check the microamps disconnect the wire on the flame sensor and put the meter between the sensor and the wire(set to DC microamps). With no flame there can be no microamp reading since the AC voltage needs to go through it to be rectified to DC. If the sensor is clean(and insulator not cracked or fouled with carbon) with AC voltage coming from the board(confirmed in step one) and the DC microamp reading low then the problem is the return path through ground. Most often that's surface rust on the burners.

Edit-Had a UGPH today and it was 100 volts to the flame sensor and 3.2 microamps.


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## Gitfiddler (Nov 28, 2011)

Thank you kind sir, I really appreciate the help!! It's nice to have someone like you around when us HVAC morons have a prob! I'll try these steps and let you know the outcome.
Gitfiddler


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## Marty S. (Oct 31, 2009)

I'm just trying to avoid having to hook up a gazillion BTU AC in the afterlife. Hopefully these good deeds will offset my teen years:whistling2:


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## Gitfiddler (Nov 28, 2011)

I decided to take a short-cut and was able to obtain a flame sensor that would work. Still no joy, so I went and bought yet another filter, put that in and took apart the wiring connections and did a cursory cleaning...I blew any dust and crud out of them and put them back together...all of a sudden everything works perfect!! I even put the old sensor back in. Been nice and toasty all night...I think sometimes if you go the simple route it's sometimes the best one!!:thumbup:


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## buckeye02 (Mar 26, 2014)

*furnace issues*

I am having an issue with my furnace ,it will not ignite it was working yesterday but now nothing anybody know what I should do at this point


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## regnell1500 (Jan 17, 2016)

*Ruud Silhouette II Furnace*

Did not see where to post new thread. Need to find out why bottom burner where flame sensor is; is not lighting. Top three burners are going.


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## yuri (Nov 29, 2008)

Burner could be dirty or your gas valve is not producing enough pressure. Also could be debris in the orifice of the burner and in some parts of the US apparently spiders get in there and nest/plug them.

Most likely the burner is dirty. There is a crossover/connector channel between the burners which may be plugged and not letting the flame cross over to light the burner.


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## regnell1500 (Jan 17, 2016)

Thanks for the most helpful reply; but with the unit and gas turned off. Is it safe to remove the burner. Seems to only be two screws holding it. And I would like to know if the burner itself could actually be bad. Thanks


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## yuri (Nov 29, 2008)

The burners can be a bit difficult to remove and line up on that furnace. I would recommend you get a Pro to do it. If it is not lined up perfectly later you could get delayed ignition or a fire. The burner is not likley bad unless it is extremely corroded or burnt thru and I cannot see it.

When you get a burner that won't light that is a VERY serious DANGEROUS condition because gas can build up in the chamber and light later and create a big boom or explosion. Not something to be taken lightly or fooled around with.

If the gas pressure is low you need a manometer to check it. Not something I recommend DIYers do.


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## regnell1500 (Jan 17, 2016)

should I turn the unit off until the unit is repaired by a pro? it is coming on and going off because the flame sensor is not seeing the flame on the bottom burner.


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## regnell1500 (Jan 17, 2016)

*Ruud Silhouette II Furnace*

Should I turn the unit off completely. It is just cycling on and off because the burner the flame sensor is on is failing to light.


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## yuri (Nov 29, 2008)

I would. It may be shooting raw gas into the heat exchanger thru the burner if the orifice is not plugged.


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