Gas valve or thermocouple?

Elijah_Borrego21

I have a williams comfort products standalone wall heater and Im having issues with it staying lit. The pilot will run fine and stay lit, but when I switch on the thermostat it will fire up and run for maybe 5ish minutes and then everything goes out even the pilot. I thought my thermocouple was the problem and replaced it but have the same issue with a new one. I then tested voltage with my multimeter and was getting around 500mv with just the pilot, but when the main burner kicked on the voltage began rapidly dropping until it hit around 150-100mv when the gas valve shut off atound 5 minutes after it kicked on. Could my gas valve be the issue? Im at a loss here and I would appreciate any input before I go spend 300$ on a new valve. Thank you!

HomerJSmith

What model? Do you have a wall thermostat? How old a unit? Voltage seem low when operating. Cleanup the pilot assembly and the thermopile connections and see if that will improve the voltage;

Erin Holohan Haskell

@Elijah_Borrego21, welcome to The Wall! I've merged your duplicate posts into one here to prevent confusion.

EdTheHeaterMan

The pilot may be too small. I just answered that query for another here. Dont know the outcome yet. https://forum.heatinghelp.com/discussion/194715/750mv-empire-heater-dv215-voltage-drop-once-main-burner-is-on

But the idea is that the pilot generator only gets power from the pilot and when the main burner is turned on, you need to look at the pilot to see what is happening. Is the pilot getting smaller? Is the pilot getting sucked off the burner and pilot generator as a result of increased air flow (DRAFT) thru the heater?

I don't believe your gas valve is defective. I think your pilot may need attention. Cleaning, new orifice, or some other adjustment.

Elijah_Borrego21

HomerJSmith said:

What model? Do you have a wall thermostat? How old a unit? Voltage seem low when operating. Cleanup the pilot assembly and the thermopile connections and see if that will improve the voltage;

Its a Williams 5001521a.
Not sure on the exact year, but I know its less than 4 years old. Theres a wall thermostat, but its on the other side of the wall, so heat is not interfering with that. Ive tripple checked all my wiring connections as well. I will clean my pilot and see if I can adjust it a little better to get more voltage. 

HomerJSmith

Often a heater has safety devices in the electrical circuit, such as, exhaust spill thermodiscs (blocked vent). The Thermopile current must pass thru these devices and if there is a higher resistance the voltage will drop. Jump these devices and recheck Thermopile voltages. Everything in the Thermopile circuit needs to be checked.
The reason that I mentioned a thermostat is that device is in the electrical circuit, not a heat issue.

mattmia2

Is there a combustion air or gas supply problem? Is the combustion air supply blocked somewhere in the appliance? Is the gas pressure staying constant? Does the flame stay consistent or does it slowly die down as the voltage drops?

Elijah_Borrego21

EdTheHeaterMan I checked my pilot oriface and and adjusted it so It evenly hits the thermocouple, no issues there. Im still having the same issue though. I get constant voltage when just the pilot is on, but as soon as the main burner kicks on the voltage rapidly drops from 300+ mv down to under 100 then it shuts off. The main burner flame is even and so is the pilot the whole time. It seems like maybe the gas valve is drawing more voltage than the thermocouple can produce when open. Is this a sign of an internal short in the gas valve?