Millivolts drop

[T28]

I have a buck stove fireplace that was installed in a recently flipped house that we bought. The fire place appears to be new and has never been lit. The on/off switch was not even installed when I started messing with this thing to get it working. The pilot will light and stay lit but valve will not open to light burners. I checked the millivolt output with a meter and they were extremely low so I ordered and replaced the thermopile unit. I now get good voltage (500+ mv) when the switch that is 6 inches away from valve unit is off. When I turn switch on millivolts drop to 3 mv. What is the cause of this?

 

[DAKSY]

Can you hear a "click" from the valve when you throw the switch?

 

[T28]

No click, complete silence.

 

[T28]

No click, complete silence.

Also, according to the troubleshoot section the millivolts are supposed to be at least 175 on closed circuit.

 

[DAKSY]

Where is the gas valve in this unit? Your pic showing the mV reading
has the multimeter probes in the firebox. Normally, the TP output
is taken at the terminal block on the gas valve, located UNDER the
firebox, & in the valve cavity...
What is the model number of your unit? I want to look at an online manual,
if there is one.

 

[T28]

Where is the gas valve in this unit? Your pic showing the mV reading
has the multimeter probes in the firebox. Normally, the TP output
is taken at the terminal block on the gas valve, located UNDER the
firebox, & in the valve cavity...
What is the model number of your unit? I want to look at an online manual,
if there is one.

The value is inside the box. There is an online manual at buckstove I believe. The fire place is a zcbb model, here are some more photos. Thank you for y

our input.

 

[T28]

The value is inside the box. There is an online manual at buckstove I believe. The fire place is a zcbb model, here are some more photos. Thank you for yView attachment 303338our input.

 

[T28]

this reading is before I replaced the thermopile . I do not have a gas pressure gauge to check the inlet gas pressure. I did replace the regulator to the correct specifications 11W.C.

 

[T28]

View attachment 303340this reading is before I replaced the thermopile . I do not have a gas pressure gauge to check the inlet gas pressure. I did replace the regulator to the correct specifications 11W.C.

I also blew out all the lines with air compressor.

 

[DAKSY]

Ok, you have a Vent-Free (aka House vented unit). The hearth shop I used to work for
wouldn't even TOUCH these units, but I have dealt with a couple on my own.
I would take a look at the rear side of the pilot tube body, near where the actual pilot
flame shoots out. There is a small hole, maybe 3/32"diameter in that body that may
be blocked with dust, dirt or pet dander. Blow it out with a can of compressed air & see
if you can light the burner. That small hole is the Oxygen Depletion Sensor (ODS), & if
it's not clear of any debris, the unit interprets that as an unsafe condition & it will not light.