# Ruud furnace issue on upgrade board and flame sensor



## yuri (Nov 29, 2008)

You don't need to change anything as it already has been done and has worked. Clean the face of the burner the sensor sits in front of with fine emory paper or clean steel wool. Make sure the circuit board is secured properly as it needs to be grounded properly or it won't sense the flame. The new board should have a diagnostic set of LEDs. You may have to remove the lower door and put duct tape on the door switch temporarily. Then fire it up and see if a code appears. You would need the instruction sheet with the board for the code. Post it here and someone may know it or find it on the net yourself. Check the porcelain of the flame sensor for cracks. If cracked or brown/black in color replace it.


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## rubberman (Oct 18, 2009)

well i wired that flame sensor to the spot on the board as the instructions said and it works now. The flame led light comes on now which it never did before.


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## yuri (Nov 29, 2008)

Good for U.:thumbup:


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## rubberman (Oct 18, 2009)

instead of buying the RHeem/Ruud remote flame sensor kit that includes the wire, connectos and that. i think i might go to radio shack and get the same stuff. be cheaper and work the same.


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## yuri (Nov 29, 2008)

Post a pic of the burner area of your furnace. Sounds confusing what you are saying. The older Rheems and Colemans used the HSI hot surface igniter as the flame sensor also. Had an extra white wire spliced into the HSI wire. The system was crap. Then they went to the standard flame sensor like everyone uses. The "remote" kit was nothing more than a flames sensor and a bracket. I think you have that already and don't need it. It is INCREDIBLY important that the flame sensor be mounted exactly where they intend it with the proper kit or you could blow up your house. The flame failure response time is less than 1 second and if you have the sensor in the wrong spot KABOOM and I am deadly serious.:excl:

This is nothing to fool around with if you don't understand it. You could be liable if someone gets hurt.


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## rubberman (Oct 18, 2009)

ok here it is. the glow igniter is on the right. the red wire behind the black gas pipe is where the flame sensor is and its mount in its bracket. in the top left corner you see the 2 white wires plus the red flame sensor wire come together in that pigtail connector. the instriuctions say to remove the red wire from that pigtail and run that to the board cause this new board monitors that different than the old revision board.


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## yuri (Nov 29, 2008)

Now I feel better. Just follow their instructions and you should be okay and use their parts.:thumbsup:


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## rubberman (Oct 18, 2009)

Here is another view showing the flame sensor mount.


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## yuri (Nov 29, 2008)

Looks good to me and the same as their newer furnaces. You should remove the burner on the far left and clean its face with fine emory. A flame sensor is not a sensor. It is a live probe with AC voltage which jumps thru the fire and converts to DC (rectifies). Then feeds thru the burner back to the board in microamps. A dirty burner prevents current flow.


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## needy (Nov 18, 2009)

*Same furnace*

Hey Rubberman, I need to install the same board. However there are two teminals missing from the new board. Any way you could post a pic of the control board. Unemployed right now and a tech wants $450 to replace the board . I can buy one for less than 200. However there are 2 extra wires and I don't know were they would go.

On the old board they are labled 24vac and com , grouped together.

Anyone else know or have the instructions for installing this board. Would like to see before ordering it, and its getting very cold in here.


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## Marty S. (Oct 31, 2009)

Easy to follow instructions come with the new board needy. If I remember correctly those go through a 9 pin connector instead of directly to the board. Everything you need comes in the box,just follow the instructions.


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## StationaryDave (Nov 24, 2009)

*How to Bench Test Flame Sensor?*

I have similar equipment and similar issues as those discussed in this thread. I went ahead and replaced the circuit board but the flame still doesn't stay on. The two green leds stay lit, but yellow flame LED doesn't come on. 

I took the flame sensor out and cleaned it with steel wool and also took its burner out and cleaned it with emory cloth. I've verified that the sensor has a good ground connection to the chassis and the wires to the board seem to be in order. 
Still no flame LED and gas cuts off.

Is there a way to bench test the flame sensor? 

Thanks,
Dave


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## Marty S. (Oct 31, 2009)

If your meter can read microamps hook one lead to the sensor and the other to the sensor wire. Reading should be over 1.8 microamps when the flame is on the rod. If less then that and the sensor is clean then replace it.


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## StationaryDave (Nov 24, 2009)

*My Prob isn't the flame sensor*

Threw on a new flame sensor...same results.
The troubleshooting chart on the panel says to check these things:
- check polarity of hvac supply 
- check continuity of sensor wire (checked that - it's ok)
- check insulation on ignitor leads (*it's igniting fine - so why worry with this?)*
- if checks are ok, replace ifc (*already done that--what are the chances this one's bad, too?*)

So I'm off to research exactly how to check the polarity. *Why would that make a difference?*


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## beenthere (Oct 11, 2008)

The HSI is still used for flame detection on conversions.


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## StationaryDave (Nov 24, 2009)

*Delay in burner firing a problem?*

Dave here again...still troubleshooting...

The burner that points to the flame sensor does indeed come on, but it sometimes comes on a second or two after the rest. Could that delay be part of my problem? How quickly after the gas comes on does the controller check the flame sensor?


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## StationaryDave (Nov 24, 2009)

beenthere said:


> The HSI is still used for flame detection on conversions.


Can you elaborate? How does this work? Is this something I should check?


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## beenthere (Oct 11, 2008)

Don't know all the ins and outs of it. But on conversions kits, it still uses the HSI for a couple seconds.
So a HSI with high resistance can cause flame lock outs. Or if the HSI's wires insulation is worn, and the neutral one is rubbing to ground, it will also register as a flame failure.


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## StationaryDave (Nov 24, 2009)

*Update...Still Shutting Off*

New circuit board, new flame sensor, new HSI...still flame fires for a few seconds and shuts down.
Got a service technician out yesterday and, after three hours of labor and getting his supervisor to look at it, he determined that there is a problem in the wiring harness. I didn't get to talk to them--I would like to know whether they used a multi-tester to actually verify this issue and specifically which wires are an issue--or are these simply the next parts they can think of to throw at it. I can't see anything that looks corroded or poorly insulated and spent some time last night cleaning connections with emory cloth (with no success).
Also, the technician removed one of the brass screw-in plugs on the gas valve assembly...and didn't put it back on. I screwed it back in place. Was that a goof? Is this dangerous to leave the valve disassembled? Should I contact them and let them know this?
So...a $400 bill from the HVAC company and another $60 and severals days wait for parts to arrive.
Dave


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## beenthere (Oct 11, 2008)

The brass cap was probably a cap for the manifold pressure adjustment.

After they return. Ask them to check what static pressure the pressure switch is seeing.
They will say that isn't the problem, or it wouldn't light in the first place.
WRONG. 
It may close until shortly after teh burners ignite, and then open because of an obstruction in the flue. Or a worn out inducer motor/fan blade.


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## StationaryDave (Nov 24, 2009)

*Fixed!*

I went back and took one more look at that troubleshooting checklist (printed on the cover of the circuit board enclosure). The first item is to check polarity. Hm. I'm not sure how to do that with my multitester, but I _do_ have one of those plug-in outlet checkers...and my sump runs on an outlet that is on the same circuit as the furnace. Sure enough...Hot and Neutral are reversed. I figured out that, last spring, when I replaced a gfci outlet that's near the breaker box (and is upstream from the furnace--bad design--if the gfci trips your whole furnace/sump circuit goes out), I must have reversed the polarity.
So I re-did the gfci wiring, checked the outlet downstairs and now it's correct.
I fired up the furnace and now it works like a charm!

Yes, I feel pretty stupid that it took me so long to figure this out. But, hey, three trained service technicians didn't think to check the polarity.

Dave


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## Engineer1 (Jan 16, 2010)

Rubberman- If you're still in this thread, I have the same issue, only worse. The house we just bought had a previous owner that was, shall we say, a danger to himself and his family. He wired the Ruud Silhouette furnace and air handler from an ungrounded outlet with a 3-sided outlet expander cube through an old alarm clock plug and cord, to a box with #18 gauge wire and a 20 amp fuse inside, then out to a power strip where the Ruud unit plugged in, and reversed the black and white wires inside the Ruud terminal box!!! Wondered why it didn't work......

Anyway, he replaced the control board to the new style with the added amber light (like yours), but left the red flame sensor wire connected to to the igniter white ones, like yours. Wondered why it didn't work...... I'd like to replace the wires and have connectors and pins but don't have the instructions. Can you reply with a brief description of where the two replacement wires go, or attach pictures of same? Better yet, anybody know where the instructions may be found online?

Thanks!
Engineer1


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## Cbrum7% (Nov 5, 2014)

My furnace would only stay lit for approx 5 seconds. What I did to fix the problem was weird but it worked. I took the white and black wires from the main power supply from the wall outlet and swapped them. This changed the polarity and it worked.


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