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-   -   Pilot light wont stay lit...Circuit problems? (http://www.diychatroom.com/f47/pilot-light-wont-stay-lit-circuit-problems-165617/)

Lavid2002 12-04-2012 10:14 PM

Pilot light wont stay lit...Circuit problems?
 
Hello everyone,


I am working on a ventless gas stove in my living room. We have had it for about a decade now and it works great! Well worked great.

Last year it stopped working because the pilot light assembly wouldn't stay lit. I replaced the thermocouple and the pilot assembly (I had no choice)

It fired right up and ran fine for another year. It has ran for about a month so far this winter but the pilot light has gone out on me twice. It was pretty stubborn to get lit again but I always managed to light it. This time, she's not coming back on. Here are a few more specifics

To light
_Press and hold, If you hold all the way down the electronic sparker lights the pilot. This unit works fine and consistently sparks over and over.

You have to hold the button down for a minute until the thermocouple warms up then you let go of the button and the pilot light should stay lit. Mine does not. I assume it's the thermocouple acting up again. I grabbed my DMM and measured the voltage difference between the two unplugged thermocouple wires (I unplugged them to measure) It starts at 0 and raises consistently to .5~.6 volts in about a minute. I don't have a wiring diagram but this seems to me like this thermocouple is working.

I don't know what I should check next. The pilot if very strong when you hold the button down to light it manually so I don't think we have a problem with the gas lines or anything like that. The electronic system isn't sensing the thermocouple right and it's shutting off the valve once I let go of the button for the pilot. The connections are all very very clean so corrosion is a non issue. I'm almost stumped.

It's a Monnesen stove, like this model.

http://www.google.com/imgres?um=1&hl...r:10,s:0,i:118

Thanks for the help! Sorry for such a detailed description I don't think I could accurately describe the issue without being so descriptive.

Protocol. 12-05-2012 12:33 AM

You will measure a thermocouple in DC voltage and you wil get millivolts. Typically 24-30mV.

The t-couple will also need to be in the flame the first 1/4-3/8 of the end. More or less and you start dropping off in voltage generation.

What kind of safety is on the device? Is the unit powered by electricity or is the safety just gas line and the thermocouple. Sometimes the safety devices themselves fail as well. The only real way to know is together restof the system running.

danpik 12-05-2012 06:42 AM

If the stove is the same as the one in the link ...then you have a milivolt powerpile, not a thermocouple. When you said you measured the voltage from the two wires that confirmed it. Anyway, I assume you got the .5 - .6 v with the pilot lit. powerpiles generaly put out ~750 Milivolts (.75 volts). The gas valves idealy like that amount but have been known to operate on as little as 300Mv. yours should operate at 500-600 with no problem. At this time I would suspect a faulty gas valve. Do you have a schematic for this unit you could post? When you said this "The electronic system isn't sensing the thermocouple right and it's shutting off the valve once I let go of the button for the pilot" it has me wondering. Normaly the powerpile is hooked up directly to the gas valve. One wire to the TP terminal and the other to the TP/TH terminal which then routs power thru the other safety devices and the thermostat (if equipped) and back th the TH terminal

oncall 12-09-2012 04:21 PM

It sounds like you have a combination millivolt gas valve. This could be why you reset.

One thing about powerpyle systems all connections must be clean and tight to limit voltage drop across the gas valve.

Also check to make sure you have a good flame at the pilot assembly and the powerpyle from the top down about 3/8" is in the flame.

If not you might have to clean your pilot assembly.

Hope this helps..


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