Furnace keeps lighting


  #1  
Old 01-22-03, 01:12 PM
MikeCrawford01
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Furnace keeps lighting

I have a RUUD GN3D108 3 burner with a Pilot light nozzle
and ignitor (white wire). An Orange wire that must run to
the heat sensor. (RobertShawSP175A)(the sensor sits on the only cross bar)The Furnace keeps clicking while running.
The burners light then go out light then go out. This keeps going
on over and over. I have read all the posts but i'm not quite sure on this model what to look for! I cleaned the furnace but was
not that dirty. The pilot keeps relighting the burners that is the
clicking sound I believe. Any Help would be Great.
 
  #2  
Old 01-22-03, 01:40 PM
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is that a spark ignition? if so the pilot flame sensor may not be sending the module the sigmnal, or the module could be bad and not receiving it.
 
  #3  
Old 01-22-03, 01:48 PM
MikeCrawford01
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Electronic Ignition is what it says. The Pilot lights then the
burners then burners go out right away then pilot lights burners
burners come on then go out. Clicks each time! How could I
Check the signal.
 
  #4  
Old 01-22-03, 07:39 PM
bigjohn
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Are you sure the module isn't SP715A? It's a recycling type module with no lockout. If I understand correctly, only the main burners are going out but the pilot is staying lit? First make sure the pilot flame and sensor are ok. Does the pilot flame fluctuate when the main buners try to lite? Is the pilot flame enveloping the flame rod? Check the voltage at the gas valve during the liteoff process. Depending on which valve you have, place the test leads on terminals TH/TR or M/C. If the voltage stays constant, replace the gas valve. If the voltage is lost, check the thermostat heat anticipator for proper setting. Look on the gas valve for the amp draw [probably .4] and set the anticipator.
 
  #5  
Old 01-24-03, 05:44 AM
MikeCrawford01
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Pilot light stays lit the whole time the burners go on and off.
I get a .7 voltage across M and C from the gas valve each time it clicks which is every 2-4 seconds. The anticipator was set to .6 and the gas valve has .5 rating still no luck. The system takes a long time before it comes back on say 15 minutes or so before the motor starts and pilot lights and burners light go out light go out in about 2-4 second intervals. What readings should I get from the heat sensor to check for proper function. The thermostat seems to work ok when I turn it on and off the furnace clicks but takes 15 minutes to start up again.
 
  #6  
Old 01-24-03, 07:08 AM
MikeCrawford01
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Setting the Anticipator to different settings the furnace might
cycle once or twice ok but returns to the gas valve clicking on and
off every 2-4 seconds(lites- clicks- then turns off burners- pilot stays lit -valve clicks burners light. (over and over).The pilot has a nice blue flame! It is strange how adjusting the anticipator lets it work for a cycle or two at around .4 to .350 but amp on gas valve device is .5 the original setting on anticipator was .6. It did cycle once at .5 and .6 then back to on and off. What else could possibly be adjusted or replaced. (Asumming is bad, but the Heat Sensor seems to work or intermittent. If control Module is bad
it would never work or also could be intermittent. The thermostat
itself could cause this problem maybe........ I have no documentation on furnace and the schematic is no where to be found . Where could I get docs on a RUUD UGDA 07EA-CR does that sound like model # or GN3D108 F3089 6772.

Thanks

Mike
 
  #7  
Old 01-24-03, 08:20 AM
bigjohn
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If the pilot is staying lit, then the flame proving circuit is ok. You should be seeing 24 volts at the gas valve M & C terminals. 3 things to check- first, see what voltage you get from MV to MV/PV at the module when the gas valve tries to open. Then, see what voltage you get from TH to TR at the module when the gas valve tries to open. Then, remove, the wire from terminal M at the gas valve and see what voltage you get from the wire you removed to C on the gas when the furnace starts and goes thru the startup sequence. You'll have to be patient and wait for it to start the inducer fan, lite the pilot, etc. The main gas valve won't rry to open because you'll have a wire removed. I suspect that the module is either bad or poorly grounded. Check all the ground connections for cleanliness and tightness. I need you to verify the module model # before I could recommend a replacement. I still think yours is SP 715A. I think you transposed the numbers while typing.
 
  #8  
Old 01-24-03, 06:03 PM
MikeCrawford01
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Thanks John!
Yes the module is an SP715A ! Will check voltages.
 

Last edited by MikeCrawford01; 01-24-03 at 06:25 PM.
  #9  
Old 01-24-03, 08:01 PM
bigjohn
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If it turns out to be a bad module, you can replace it with a Honeywell S8610U or a Robertshaw/Uniline 780-715.
 
  #10  
Old 01-25-03, 09:15 AM
MikeCrawford01
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The voltage from MV-MV/PV is about .9 fulcuates a bit to
.7-.5-.9. volts
The TH-TR .7 volts.
Tests on gas valve opening.

If Module is bad could I replace with another
Robert Shaw SP715A

Im not quite sure how you want me to run the other test.

Remove the M Wire from gas valve and check voltage
from disconnected M wire and C on valve.
 
  #11  
Old 01-25-03, 03:39 PM
bigjohn
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Yes, disconnect the wire from M and check from the disconnected wire to C when the gas on a call for heat. Something is amiss here. TH/TR are on the INCOMING or power supply side of the module. You should have 24 volts there all the time whenever the thermostat is calling for heat. Either the gas valve is bogging down the circuit due to a high amp draw or something upstream in the circuit is malfunctioning. Loose connection somewhere, bad/corroded contacts in the limit switch, poor ground connection on the module, check to see if one side of the transformer secondary is grounded. Try testing from M on the gas valve [wire connected] to a ground in the furnace that you know is good. Also, go from TH to GND on the module. Any chance you have an amp meter? At the furnace, locate the cable that comes in from the thermostat. Remove the wires from R and W termianls and install a jumper from R to W. Turn the furnace back on and run all the voltage checks again. The module may not be the problem and I would hate to see you drop $100 only to find out the porblem is elsewhere. As for your question about another SP715A. I may be wrong, but I don't think it's made anymore which why I looked up a cross reference.
 
  #12  
Old 01-25-03, 11:17 PM
MikeCrawford01
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Voltages AC (NO jumper between R and W)

M-C 23.7 volts when gas valve clicks on.

MV-MV/PV 23 volts gas valve clicks on.

TH-TR - 24 volts gas valve Clicks on

M - Ground 25.2 Checked with GRN wire ground at ground area
next to Control module.

TH - Ground 25.2 Same as above.

M wire off at Valve to C on valve - 25.2 volts
Pilot lite comes on no burners.

The gas valve clicks on and off so fast I don't know if the
MV-MV/PV test drops to 0 Volts(Seems it does not) when gas
off condition occurs. Seemed liked it droped but to 19V possible (around that)
then back to 23 on gas valve open for burners.

The system will cycle the first time only but about 3/4 the
way through then the burners go off click lit go off click lit
but the pilot stays lit. (anticipator set to about .5 on dial)
Lower anticipator setting let the system cycle one maybe two
times but never more than that.
 
  #13  
Old 01-26-03, 08:04 AM
bigjohn
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I reread my manual on your module and found that the pilot gas stays on if the piot burner goes out or if the module does not sense the pliot flame properly. Most modules shut down the pilot gas if the pilot flame is not senesed. We may have been barking up the wrong tree. Look to see that the pilot flame covers the top 3/4" of the flame rod. Shut off the power, look at the end of the flame rod for a residue buildup; make sure it's clean. With your ohmeter, check the continuity between the flame rod tip and sense termianl on the module. You should see perfect continuity- 0 ohms. If not, check the resistance on the flame rod and the wire separately. [end to end on each one] If that's ok, check from the flame rod tip to the GRD terminal on the module. You should NOT have any continuity. You may want to check them cold and then run the furnace, let everything get hot, quickly shut it off and repeat the checks when it's hot. I'm thinking that the flame rod or the wire back to the module may have resisitance or be leaking it's current to ground when they get hot. Sorry for the confusion, the pilot staying on threw me a curve ball, most modules shut off the pilot gas when the flame sensing/verifying circuit is not up to snuff, but the book says the pilot gas stays on along with the sparker. Here is the sequence of operation verbatim:

Step 1;
Thermostat contacts close calling for heat. Power is sent to the SP715A. The SP715A opens the first valve on the gas control supplying gas to the pilot, and energizes the high voltage spark at the same time.

Step 2:
The spark continues until the sensor circuit detects the rectified current through the pilot flame. If the pilot flame is not sensed the spark and pilot gas remain on for as long as there is a call for heat.

Step 3:
When the ignition control module senses the presence of the flame it energizes the second valve in the gas control. The SP715A continues to spark for a few seconds afer the 2nd valve opens to ensure stable operation.

Step 4:
The SP715A continuously monitors the pilot flame while the burners are in operation. If the pilot flame goes out, the SP715A will shut off the main burners, initate a spark, and attempt to relite the pilot.

Step 5:
When the thermostat is satisfied, power to the SP715a is dsicontinued and all burners shut down.

Reading in between the lines in Steps 2,3, & 4, you can see that if the pilot remains lit but the flame rectification current drops below the threshhold value to keeo the 2nd operator energized, we would see the symptoms we have now which why I'm thinking that the flame sensor or the wiring from the flame sensor to the module may be the culprit. The flame sensor body is ceramic and it may have last some of it's capability to maintain infinite resistance to ground, especially when it's hot. Do the checks and let us know what you find.
 
  #14  
Old 01-27-03, 02:06 PM
MikeCrawford01
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Continuity seems to check at 0 ohms!
You will get a spike when probe first touchs connector.
Cleaned the sensor again but it is clean. Real hard to get I at.
 
  #15  
Old 01-27-03, 03:00 PM
bigjohn
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Continuity where? From the flame rod to the sense terminal or from the flame rod to GRD?
 
  #16  
Old 01-27-03, 03:43 PM
H
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MMMMMM could be!

Could be main supply gas pressure is too low because of demand, or outlet pressure is not 3.5", could be a bad main gas valve solenoid on your gas valve, amp one of the wires, could be a bad modile.
A pressure gauge would rule out gas pressures. an ammeter the solenoid, .. If all else fails...put in the S8610U 1003, oh....make sure the air filter is clean and the blower runs.
 
  #17  
Old 01-27-03, 06:12 PM
MikeCrawford01
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No continuity to Ground sorry I did not post that. Well
I changed the thermostat no luck need replaceded anyway.
Guess I will Replace Sensor rod next. I will pull Rod and take it somewhere to get proper one. I have two furnaces one upstairs
one downstairs. This is the upstairs furnace where my 20 year old daughter lives. We are using electric heaters to keep her
room warm but the rest of the upstairs is cold. The furnace upstairs is closer to the main gas inlet and a new filter was used.
Granted that this has been one of the coldest months I remember
we never had a gas flow problem in the past. I did shut down
the downstairs furnace anyway for a test no change.
 
  #18  
Old 01-27-03, 07:00 PM
jkebxjunke
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gas pressure---frosty regulator?

Is it possible that maybe the regulator has gotten frost in it?
I had an LP (propane) regulator that would get frost in it... and loose heat in tha back half of the house along with hot water heater. Gas company reccomended pouring a pan of warm to hot water over the regulator--it did the trick.
Also another problem I had with propane regulator... the regulator would not respond to minute changes in gas pressure. According to the gas tech who changed it --it had just gotten old and the diaphragm had gotten stiff.

Just a thought.
PS when you run a farm you learn how to deal with just about anything.--especially when you have 20,000 3 day old chickens needing heat when it is 10 degrees on a saturday night.
 
  #19  
Old 01-27-03, 09:45 PM
MikeCrawford01
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The Sparker,Sensor and Pilot Tube are all hooked
together. I removed the support that held the sensor
assembly in place. The Pilot tube has a nut on it and
I assume a flanged end that goes into the pilot tube.
The pilot line then runs back to the gas valve(Module) where there is a nut on the side of the gas valve (module).

Would you loosen the nut on the pilot tube to remove the
the sensor assembly or the nut on the gas valve module?

If the pilot tube then the line from the gas valve module
for the pilot light stays in place.
or
The nut from the gas valve module and the whole assembly
pilot line,pilot tube sparker and sensor come out.

I just don't want to run the pilot gas line.
 
  #20  
Old 01-28-03, 02:42 AM
bigjohn
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It will be easier to work the tube at the gas valve end. It's a flare nut, just unthread it. Before replacing anything, take a wire brush and clean the surface where the pilot assembly attaches to the burner housing and also clean the underside of the pilot assembly bracket and try it again. Make sure that all ground connections in the furnace are clean/tight.

Edit:

I've been thinking about this and would like to suggest that, if you decide to do something with the pilot burner/flame rod/sparker assembly, replace the whole thing. We had a gentleman here about a month ago where we tracked down the problem to the assembly which he replaced. However, he used the orifice from the old pilot burner and the furnace still wouldn't work. He took the assembly back out, inserted the new orifice and, Voila, it worked just fine. His problem all along had been the pilot flame wasn't enveloping the flame rod sufficiently. By replacing the whole assembly, both the pilot burner and flame rod are new which eliminates them from the equation.
 

Last edited by bigjohn; 01-28-03 at 05:11 AM.
  #21  
Old 01-28-03, 08:18 AM
busterm
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Mike, please don't take this the wrong way; but, considering the nature of your questions and the fact you don't have schematics or operating instructions, you are taking a big chance working on this furnace yourself. I hope you will strongly consider hiring a professional.
 
  #22  
Old 01-28-03, 11:22 AM
MikeCrawford01
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The sensor was being enveloped by the flame approx. 3/4".
The sensor rod was bright orange.
Will take your advice to replace the whole assembly.
(If I can find one.)

BigJohn has been right on to this point so I believe I am
getting Professional Help. Have you read BigJohns posts to
other questions he knows his stuff.
 
  #23  
Old 01-28-03, 11:43 AM
busterm
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Big John is obviously an expert, but he isn't there with you. I don't intend to be a busybody so I won't bother you further. Hope all turns out well.
 
  #24  
Old 01-28-03, 08:14 PM
MikeCrawford01
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After removing the pilot assembly the flame sensor was not
as clean as I thought or could see. It is tucked neatly behind the
support which made it hard to get at and clean. After removal
and cleaning the rod first with sand paper then polishing and
cleaning for about an 1/2 hour with steel wool the flame Rod
was clean. The reason for using steel wool is that emery cloth
and sand paper can leave a film. The sand paper made it
easier to remove the heavy carbon buildup which if not closely
inspected and cleaned can cause Problems. The Steel Wool cleaned the surface of any sand paper residue and polished the
Flame Rod nicely. The flame rod should be removed for a proper
cleaning. It is nice to say that the furnace has run flawless for
the last 6 hours or so. The Flame Sensor was dirty. I would like
to thank all those who replied and especially BIGJOHN for taking
the time to help.

Thanks Again !

Mike
 
  #25  
Old 01-29-03, 02:40 AM
bigjohn
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Way To Go! I'm glad it turned out to be something simple and easy to fix.
 
  #26  
Old 03-01-05, 01:03 AM
RoscoJames
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Furnace keeps lighting - may not be done yet

BigJohn and Mike
I've been having the same problem, so have followed your thread closely. My first solution about two weeks ago was what you've just discovered - the flame sensor was replace and all worked well. After a little while, I'm back where I started. I've got the Robertshaw sp715a ignition control and went through all the voltage checks, etc. It's 3am in the morning and I'm once more trying to generate enough heat to get through till tomorrow. Then i will hunt down a replacement for the module (which i always doubted anyway). What finally happened is no spark and no pilot gas, but 24V across TH and TR. If i switch the power on and off, most of the time the pilot will light, then the main gas will light. Once it goes off (and it goes off before the temp is raised), the pilot gas and the spark won't activate. Fact is, it could be the module as well as the limit control. Hard to know. I'm willing to put the $100 down as part of my training. I just don't know where to get said module replacement. (Kansas City Area)
Larry
 
  #27  
Old 03-01-05, 01:11 AM
RoscoJames
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Furnace - ignition replacement

BigJohn
Saw your suggestion on cross over replacement parts for the SP 175A. I'm in the Kansas City area. Any idea where a fellow could could those parts?

Thanks

Larry
 
  #28  
Old 03-01-05, 07:23 AM
RoscoJames
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Furnace replacment part sp715a

I found a local company after all. It was late last night (this morning) when I asked you for a resource. Sorry - It's just a matter of calling around. I'll let you guys know if the new ign module solves the problem. Good work.

RJ
 
  #29  
Old 11-24-08, 08:25 PM
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Question SP715A vs. 780-715 (SP715U)

Hi all,
I have a 23 year old RobertShaw SP715A ignition control module in my RUUD gas furnace. I want to keep an extra ignition module on hand. Although obsolete, I still see the SP715A available on-line

Does anyone know what the difference is between the RobertShaw SP715A ignition module and the new replacement for it, the RobertShaw SP715U (780-715)? I think there's a Honeywell replacement too, which I was hoping someone out there has experience with.

Also, the 715A and 715U both appear to be identical plug & play type modules (with gas and electrics turned off, of course). All connections look to be the same. So, I'm just wondering if my home will definitely explode when doing this install? It seems pretty cut and dry.

Any help with this is appreciated.
Guitartec
 

Last edited by guitartec; 11-24-08 at 10:48 PM.
  #30  
Old 11-27-08, 08:28 PM
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Question Furnace flame turns on/off/on/off

I read the threads and I have a similar issue. I have a 7+yr old HEIL furnace (NTC6075FBA2) with a Honeywell board (ST9120c4057).
Here is what happens: When the thermostat click to turn on the furnace, the exhaust fan turns on, then the burners light. Then the blower turns on, so far so good. Then about every 10-20 seconds, the burners turn off, wait 5-10 seconds, then light and run for 10-20 seconds. This cycles over and over until the thermostat tells the furnace to turn off.
There are 3 burners, and they all light, nice blue flame. Also, I just had a repair tech replace the exahust fan (which was making a grinding noise) for $500, so I don't think that is the issue, but am willing not to rule it out. My guess is a bad flame sensor???
 
  #31  
Old 12-03-08, 06:36 PM
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fixed: water in a hose

ok...fixed my issue.
there is a vacuum line that connects between the exhaust blower and a sensor, and it was filled with water..
I emptied it out and all is well
 
  #32  
Old 12-04-10, 01:29 AM
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I'm having the same issue as iblisrocks "there is a vacuum line that connects between the exhaust blower and a sensor, and it was filled with water..
I emptied it out and all is well" I had a tech. come out and changed the exhaust motor out on my unit also. It wasn’t two days later this same thing happened to me and then it happened again 3 nights later. Is this something that the tech. did wrong when hooking up my motor or just a fluke. I never had this issue with my old motor, but it needed to be replaced and that’s when I started having trouble with the vacuum line getting water in it. Any solutions.
 
 

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