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Open Roads Forum  >  Tech Issues

 > Suburban Oven Pilot Won't Stay Lit

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jblauert

Tucson, AZ

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Posted: 12/17/11 11:29am Link  |  Print  |  Notify Moderator

I have searched the forums, but think my issue may be different my knob is not making contact and my thermocouple from the pilot is not a tube.

It is a Suburnban SRNA3SBBM which is a match light oven. We have gotten it to light a few times when we first got the used toy hauler, but the last few attempts have failed. The pilot will light, but when you release the knob to turn up the gas the pilot goes out and there does not seem to be a way to just light the main burner (safety and all ). So, it seems that the pilot thermocouple is not working correctly?

The sensor above my pilot looks different from the ones I have seen online in that it has 2 wires coming out of it. One goes to a screw on the frame (ground) and the other goes to a mechanical switch (normally closed) that is opened when you turn the knob. The other side of the switch has a wire that goes to the back of the brass gas valve.

I am trying to test if the thermocouple (assuming a mechanical switch) if working, but I am not sure what is normal. There seems to be no resistance across the thermocouple so it is currently closed to ground. Also the wire that connects to the brass valve also seems to be connected to ground.

I do not think there is a source of power to the range at all. Really struggling to understand how this system is supposed to work so I can test and replace whatever seems to be broken.

Any help is greatly appreciated!!!

Ka Ron

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Posted: 12/17/11 12:43pm Link  |  Print  |  Notify Moderator

Sounds like you have a thermopile, not a thermocouple. They do the same thing and that is keep the gas valve open by sensing the flame. They generate a small millivoltage of electricity that usually holds a magnet in the gas valve in the open position. When you light your stove and then let up on the knob and the flame goes out is is a faulty thermopile or thermocouple. Only other thing would be faulty valve.

Good luck


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Francesca Knowles

Port Hadlock, Washington

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Posted: 12/17/11 02:56pm Link  |  Print  |  Notify Moderator

Hi

This probably isn't what you want to hear, but that model Suburban Stove has an oven-related recall out...

Hopefully yours isn't one of the following serial number series'.

From Recalls Tagged as Oven
" CERTAIN SUBURBAN THREE BURNER MATCH LIGHT GAS RANGES, MODEL SRNA3SBBM, SERIAL NUMBER RANGE BEGINNING WITH 063809986 AND ENDING WITH 063810173, MANUFACTURED ON SEPTEMBER 21 AND SEPTEMBER 22, 2006, P/NOS. 2863A AND 2863D, INSTALLED AS ORIGINAL EQUIPMENT ON CERTAIN RECREATIONAL VEHICLES. THE OVEN THERMOSTAT CONTROL VALVE CAN ALLOW GAS FLOW TO THE OVEN BURNER WHEN THE OVEN CONTROL KNOB IS PUSHED IN AND NOT FULLY IN THE CORRECT POSITION TO LIGHT THE PILOT. "


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jblauert

Tucson, AZ

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Posted: 12/17/11 07:05pm Link  |  Print  |  Notify Moderator

I did happen to see that recall and my serial number is not within that range, but thanks for the heads up.

After reading about how the thermopile should provide a voltage I went and took another look. Things made a lot more sense when I realized that the knob held the mechanical switch OPEN and then closed the circuit when it is turned on (so I can now understand how a voltage from the thermopile would reach the valve.

I pulled the lead off of the mechanical switch, hooked up a voltmeter, and applied a stove lighter to the thermopile ... I was slightly disappointed when I actually saw a voltage ramp up, because that seemed to indicate that it was working properly and may mean the valve was bad.

So, I hooked everything back up, turned on the gas, purged the line through the stove top and then tried to light the oven pilot. It lit, released the knob ... and IT STAYED ON!!! Now I was very pleasantly surprised ... turned it on and off 3-4 times and it was way easier than it ever was.

Then I thought maybe it was the knob, so I put the oven completely back together (front cover, top, knobs and all). And the oven fired right up again.

This is not the first time that I have taken something apart, found nothing, put it back together, and suddenly it works. I am not going to complain and just cross my fingers and hope that it keeps working while out camping.

Thanks for the info. I have not written before, but spend a lot of time sifting through all the great information here.

Tomorrow I think I am going to tackle the Honda 2000i carb cleaning tutorial I found here.

Ka Ron

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Posted: 12/18/11 03:34pm Link  |  Print  |  Notify Moderator

jblauert wrote:

I did happen to see that recall and my serial number is not within that range, but thanks for the heads up.

After reading about how the thermopile should provide a voltage I went and took another look. Things made a lot more sense when I realized that the knob held the mechanical switch OPEN and then closed the circuit when it is turned on (so I can now understand how a voltage from the thermopile would reach the valve.

I pulled the lead off of the mechanical switch, hooked up a voltmeter, and applied a stove lighter to the thermopile ... I was slightly disappointed when I actually saw a voltage ramp up, because that seemed to indicate that it was working properly and may mean the valve was bad.

So, I hooked everything back up, turned on the gas, purged the line through the stove top and then tried to light the oven pilot. It lit, released the knob ... and IT STAYED ON!!! Now I was very pleasantly surprised ... turned it on and off 3-4 times and it was way easier than it ever was.

Then I thought maybe it was the knob, so I put the oven completely back together (front cover, top, knobs and all). And the oven fired right up again.

This is not the first time that I have taken something apart, found nothing, put it back together, and suddenly it works. I am not going to complain and just cross my fingers and hope that it keeps working while out camping.

Thanks for the info. I have not written before, but spend a lot of time sifting through all the great information here.

Tomorrow I think I am going to tackle the Honda 2000i carb cleaning tutorial I found here.


Could have been a bad contact at the connection you took off. When you put it back together you made prper contact.
Good Job.

jblauert

Tucson, AZ

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Posted: 12/31/11 03:58pm Link  |  Print  |  Notify Moderator

Well, went camping last week and the pilot lit with no problem and then the oven lit. Set the temp and put our food in and found a few minutes later that the oven had gone out completely. Plenty of gas in the tank. Could not get the pilot to relight. So, apparently my "fix" did not work.

Could the thermopile still be bad and causing the problem? Seems odd that it would die after the oven was lit. Not sure if it died after reaching temperatuer and then just shut down or what ... may have to experiment if I can get it relit.

Any other thoughts?

Thanks.

jblauert

Tucson, AZ

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Posted: 10/15/12 12:13am Link  |  Print  |  Notify Moderator

Ugh ... still need to get this fixed.

Does anyone know how much voltage is required to keep the valve open? I noticed tonight that using a lighter I have about 17 mV at the thermopile connector, but only about 8 mV on the other side of the mechanical switch that is closed when the knob is turned on. Wondering if that switch is somehow bad ... BUT ... when I pull off the connection I get 0 resistance across it, so the voltage drop seems odd.

When I used a piece of 12AWG wire between the thermopile connector and the connector to the valve ... everything seemed to be working fine. Pilot stayed on the entire time. The only "danger" with just skipping the mechanical switch is that the pilot stays on when you turn the knob to off. When you blow out the flame, the gas turns off. So, that may be the easiest solution ... just remember to blow out the pilot so the gas does not get used.

A couple odd observations:
- The thermopile connector and the valve connector have continuity with ground. This surprised me ... sound normal?
- When I measured the voltage on the loose thermpile connector I got about 27 mV, but when it was connected to the mechanical switch and the valve was connected to the other side, I got the 17 mV and 8 mV as mentioned above. Not sure why having the switch connected would lower the voltage ... unless it was just due to lower heat of just using the lighter and not the actual pilot.

Curious if anything jumps out at anyone as odd ... or if other suggestions to test come to mind.

I may see if I can find another switch cheap and see if that fixes things. If not, I may just opt to wire the thermopile directly to the valve.

Dusty R

Charlotte Michigan 48813

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Posted: 10/15/12 06:15am Link  |  Print  |  Notify Moderator

A few older gas furnaces used that system. We called them powerpile.
If I remember right.
A powerpile produces 750 ml. volt DC.
A thermocouple produces 250 ml. volt DC.
Try Googling "Powerpile"

Many of the "gas logs" fire places today use a powerpile.



Dusty

* This post was edited 10/15/12 06:35am by Dusty R *

jblauert

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Posted: 10/15/12 10:24pm Link  |  Print  |  Notify Moderator

Looking at the powerpiles online, looks like they are larger and have 2 wires. I think mine only has 1 wire (although there may be a ground wire too I guess).

Last night I got it working and was finding if I wiggled the connector to the manual switch the pilot valve would turn off ... so I started again thinking it could be internal to the switch. At this point it seems to be working, no matter how much I wiggle stuff around, so may have been something loose.

I would like to find a reference to see how much voltage I should be reading from the "sensor" {I see all the parts diagrams call it a thermocouple}. I suppose it could be weak leading to the valve sensitivity, or it could be something in the mechanical switch.

I guess I will keep messing with it and try to use it see if it stops again.

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