Hearthstone Luno - pilot on, main burner on and off randomly

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Dynastyss

Member
Oct 29, 2017
6
Lake Tahoe
Hey there.

I am trying to diagnose a problem from 300 miles which is always hard. We have had a hearthstone luno 8610 for nearly 8 years as the main source of heat in our cabin. It’s natural gas, and usually works beautifully.

Of late it has been finicky, and becoming increasing finicky. In short, the pilot is on, and the main burner doesn’t like to turn over. The only way to consistently get it to turn over is adjust the hi/lo pressure knob on the valve. It will run for 30 minutes to multiple hours then die. Rinse and repeat.

I am trying to get a sense of what I should do or buy before driving up to fix it.

Is the thermopile going out? Is the pilot light not strong enough? Is the valve starting to fail?

Any theories?

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DAKSY

Full Time RVer
Staff member
Dec 2, 2008
9,350
Wherever we're parked
You need to use a Multimeter, set to milliVolts, & read the thermopile output.
Under the pilot, the reading should be in the 550+/- 50mV range.
Under the burner, it should read 220 +/- 20 mV.
The readings should be taken at the TH-TP & TP spade connectors on the
valve's terminal block.
Let us know what you find...
 

Dynastyss

Member
Oct 29, 2017
6
Lake Tahoe
You need to use a Multimeter, set to milliVolts, & read the thermopile output.
Under the pilot, the reading should be in the 550+/- 50mV range.
Under the burner, it should read 220 +/- 20 mV.
The readings should be taken at the TH-TP & TP spade connectors on the
valve's terminal block.
Let us know what you find...
Hey! I totally agree and I should but I was kind of hoping to have myself some working theories and parts before I make the 300 miles to repair it. Sounds like you are thinking of the thermopile issue. If it was weak would playing with the hi/lo regulator be enough to jump start it?

Thanks
 

Fingerlakes Fireplace

Burning Hunk
Jan 9, 2017
188
Upstate NY
It could be an issue with the switch and or wiring connected to the switch. Test the voltage of the thermopile output, and then test the voltage drop across the switch and wiring circuit.
 

Dynastyss

Member
Oct 29, 2017
6
Lake Tahoe
So I drove up the 300 miles to check it out. Brought a new thermopile just in case. Honestly I am not sure what the issue was but it seems to be working ok now?

Tp - 565mv and 225mv when burner is on. Didn’t replace it.

Sit 820 valve - 2.2 ohm

Thermocouple - nice blue flame on the pilot

I opened it up, vacummed out the dust, made sure the burner ports weren’t visibly blocked and took the rough side of a new sponge the pilot assembly parts. Buttoned it up, pilot came on easy, main burner took a little bit to turn over but once it did it has been super responsive.

I can’t tell if it is going to fail again, it is fixed, the snow on the pipe is melted enough that more oxygen is getting in or what. But fingers crossed