Old gas wall heater. Pilot light trouble.

emilyenorris

We have an old Coleman gas wall heater that was in our house when we bought it. We have never had any trouble with it until one day we turned the heat on the thermostat all the way down. That same day when we tried to turn the heat back up, the pilot light had gone out. Now it will not remain lit. We replaced the thermopile thinking we were not getting enough millivolts. That did not help. As long at the gas valve is set to light the pilot and you are holding it in that position, the pilot will stay lit (we have held it there for a few minutes). As soon as you turn it to on, the pilot light goes off. What should be our next step? I have attached a few pictures of our heater.

Thank you

JUGHNE

In a powerpile system there is very little electrical energy available. Any hi resistance connection can cause grief.
Assuming you lack a millivolt meter etc, you could check all electrical connections to be tight.
This includes the t-stat and I would loosen and reset all the screws involved.
You can also jumper the wires at the tstat and try to light. That eliminates that switch in the circuit.
But the pilot should stay lit regardless of tstat action.

The pilot light could be dirty and not producing the flame/heat it should.

Alan (California Radiant) Forbes

If the thermopile is generating enough electricity, then there is something wrong with the combination gas valve.

As I understand it, a thermopile generates 70-100 millivolts when there is a flame heating the probe. That small amount of electricity is enough to pull in an electromagnet which holds opens the pilot valve, allowing you to release the dial which manually holds the pilot valve open. You can then turn the dial to "On" and the heater starts working when there is a call for heat.

Sometimes, that electromagnet stops working and it won't stay open when you release the button. In your case, you say that the flame goes out when you turn the dial to "On". Can't say I've ever seen that, but replacing the gas valve may fix it.

unclejohn

Tim will at some time chime in but until then, is the pilot light strong enough. You should be able too hear it. Did you clean the thermopile? Tighten all connections?

the_donut

Hard to see, but is that a crack in the casing of your gas valve?

unclejohn

The thermopile looks like it is installed cockeyed. Is the flame hitting it?

Tim McElwain

You need to take a complete set of Millivolts. The generator should be putting out at least 650 to 750 millivolts . There are two parts to that gas control. One is the gas valve coil the other is the magnet assembly.The procedure for testing taken from my manual on Powerpile is available here on the wall

Tim McElwain

Go to "Before you ask" then go to "Heating Museum" followed by find "Tim McElwain and then "Procedure for Troubleshooting Powerpile System. If it should prove to be the magnet in the gas valve the entire valve will have to be replaced with a VS820A from Honeywell.

emilyenorris

This is probably a dumb question, but are the millivolt readings taken with the pilot light lit? If so, I will need someone to hold the knob to the light position since it won't stay lit. Wanted to be sure I did it right. Thanks.

JUGHNE

Yes, the millivolts are generated by the pilot light heat applied to the millivolt generator. That power must then go up to your tstat and come back to open the gas valve. That is why the wiring must be pristine. But you have to get the pilot to stay on first.

emilyenorris

I had someone hold the pilot light on to get these readings. #1 with generator disconnected from the valve 600
#2 with a closed circuit everything connected 207
#3 jumping the TH 170
#4 TH readings 38
Then I took a reading at the thermostat wires at the thermostat 560.

As soon as the pilot light switch was released, the pilot went out.