Gas and Oil Home Heating Furnaces - Ruud Gas Furnace burner problem

I have a Ruud Gas furnace about 18 years old. I set the t-stat the other night and yesterday morning the heater did not turn on. I did here the igniter just keep clicking but did not have time to look at it. So last night I set the t-stat and the igniter started clicking and then I look in side and did see the pilot start and stay lit but the igniter just keeps clicking and will not turn off and the burners will not come on.
Thanks for your help.

Sounds like the flame rod near the pilot may need to be cleaned.

It can be cleaned with green scotch bright pad.. (NOT sand paper).

When was the last time you had a full cleaning/tune up on this?

Thanks Jay

I never had it full cleaning or tune up in the five years that lived in the condo but that is what I think it might be is the heat rod will try that tonight.

No good tried to clean the flame rod and this did not fixed the problem

Make sure the wire from the flame rod is snug on the ignitor board.

Also, make sure the sensor is on the pilot.

Does the pilot flame itself come in contact with the flame sensor you cleaned, or is this flame sensor on the other side of the burners away from the pilot?

If, say, the flame sensor was over on the other side to sense burner flame instead, you may have issue with amount of pilot flame. Some furnaces have pilots that generate milliamps through pilot assembly and register at control board.

In either way, does the pilot flame look pretty good, say maybe an inch of flame or so, or is it something pretty puny and or yellow?

Without seeing your unit, I am guessing that pilot flame is either not sufficient, or the pilot is not generating the current it should to record at the board (if applicable) or the board is bad.

Pilot operated furnaces can have histories where orifice gets obstructed. Orifice is at tip down where it is burning and requres removal and cleaning out. Very tiny hole in there. You do not want to use tool that enlarges hole! You first need to hold orifice up to a bright light to see if you see a perfectly round pinpoint of light coming through it. Can first try to blow out with air compressor, or something that merely brushes or cleans it free. I have already cleaned them by removing strand of wire from a wire brush (needles and pins are generally too thick, believe it or not)

Keep posting back so we all know what solved your problem, please.

The pilot flame looks fine to me about and inch long and the flame complete covers the flame sensor which will start to turn red after 5 to 10 secs. The flame is mostly blue with some yellow at the end

The flame sensor looks like this http://arnoldservice.com/Amana_Janitrol_Armstrong_B1172601_side.jpg
Which is a push in style the wire is sung.
This is odd to me because my furnace is a Ruud and from what Arnold Service web site says this sensor is for Armstrong, Amana and Goodman

Furnace is a Ruud model UGDD-04nc-cr

Ignition Control is:
Robertshaw Model # SP715A

Hi Mad:

The next test is to check the feedback circuit to the module from the flame rod. Basically the way it works is small curent is passed thru the flame where it is rectified to pulsing dc. Each brand of module has a threshold current below which the midule will not work. The test is to hook up a multmeter in series with the rod and the module. Also, check to see if 24 volts is getting to the gas valve. Could be it's sticking. Many furnace manufacturers use the same ignition systems they don't make the systems, just buy them from vendors.

Also, check to see if 24 volts is getting to the gas valve. Could be it's sticking.

I am betting against the gas valve due to his repeated ignitor clicking. Have a hunch his problem is before the furnaces acknowledgement to send 24v power to gas valve, IMO. I'd be more inclined if I had to pick one of the two expensive furnace parts, that the board is bum at where the board acknowledges the dc milliamps from the flame sensor.

Will try the volt test on the flame sensor. any post the results. I starting to think that it is a bad ignition control unit.

I'm always hesitant to tell people on a messageboard forum what they need for sure is some expensive furnace part. It's your money; not mine. We all make mistakes in diagnosis, you know? Even doctors with lots of experience.

I have an advantage over some people in the fact I can go to my furnace man if need be and say, "Hey Denny, do have an extra board for a 'such and such' furnace I could try?" The other advantage is IF I do make a mistake (seldom :) ) that even if the landlord has to bite it, he knows I have saved him hundreds and hundreds of dollars over the years.

But if your problem is not the flame sensor or associated connections, it does sound to me like it probably is the board, with that clicking of the pilot that will not go away even after the pilot is on. It be nice if more experts here would voice their opinion here, and then it be like the show "Who Wants to be a Millionaire" when they poll the audience. :)

Thanks, everyone for the feedback. I test the flame sensor with the volt meter in series it shows a small current about 1 volt or less. One thing I did notice is when the flame sensor was not connected and I had not jump the line the Ignition Control would not try to start the igniter.

Current is measured in amps not volts. With your meter leads placed in series with the flame sensor you want to use an low amperage scale on your meter. You're looking for something in the area of 1ua to 2ua[microamps]. If you're getting that, then the module is probably bad. If you're not, check the ground connections at the module and the sensor for cleanliness, and try cleaning the flame rod again. Also, check to wire from the flame rod to the module for continuity. Let us know what you find.

Well here is one for the books. This time I check for amps not volts, meter read around 800 to 900 milliamps. But here is the good part during the test the igniter lit the pilot and after about 8 sec the igniter stopped and about 8 sec after that the burners started up. So then I turn the t-stat off and hooked the unit back and tested the unit and it worked. But since it is about 75 here I will need to see if it is going to work on a cold day correctly.

That's how it's supposed to work. It spark lites the pilot, proves the pilot flame, shuts off the sparker, then lites the main burner from the pilot burner. My guess is you removed some corrosion, unkowingly redid a connection, or maybe made the flame sense wire whole again. I suggest you try it once a day before cold weather sets in again.

:) :thumbup: THANK YOU! :thumbup: THANK YOU! :thumbup: THANK YOU! :thumbup:
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I work in a financial firm so apparently has minimal knowledge of the construction field. My minimal knowledge is based on my own logics when trying to understanding how things work inside the house. My husband is import/export business man with some talents of fixing things. But we both always like to “do it ourselves,” if we can.

We were struggling as what happened to our furnace. Everything seems to work fine but just no heat out. So I decided to search via Google and found this posting, http://forum.doityourself.com/showthread.php?t=323437. Based on my logics and analysis of the contents, I decided to follow the advice, so I bought the flame sensor. Again, thanks to Google in helping me to find a very good price for the flame sensor.

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