Heatilator gas fireplace has pilot but no flame.

[JimDaugherty]

Thank you for your help in this forum. I have searched the forum and don't see my problem addressed yet. If so, please direct me to the answer already listed.

I have a Heatilator Model ND4236, Serial GA1005589, Mfg. Date 2403 (mid June, 2003?) natural gas fireplace, which was installed in 2003. It has a standing pilot light, which ignites with a piezoelectric (press the red button) starter. The pilot light lights okay. However, it has been harder and harder to get the flame to burn when I turn on the wall switch.

I can do some diagnostics as shown in this YouTube video, “Diagnostic Testing For Gas Pressure and Gas Millivolt Valves.”

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I have a gas furnace and gas water heater; both work fine. The furnace was serviced earlier this week so I doubt that I have a gas pressure problem. I have a RadioShack multi-meter and can check the thermopile. Terminals TH/TP and TP read .672. The video indicates 325 millivolt minimum, readings are generally 400 to 700 millivolts. So thermopile seems okay at .672.

I have clearance problems for the thermocouple testing and I don't have a replacement thermocouple if this is an issue. There is a metal plate attached to the bottom of the fire box with four wing nuts, This plate has the gas control valve, the pilot light, and the starter attached. The gas supply flex pipe appears to have enough flex to allow the detachment of the metal plate to get this assembly out for service on an installed fireplace. Is that how it is done?

The pilot light assembly has three connections. They are in order: a copper color, a silver (aluminum) color and a white fabric covered (one blue and one black dot painted on it) connections. I believe that the silver one is the pilot gas supply. It appears that of the other two, one determines if the pilot is lit to allow the pilot lit supply to stay on, which apparently is working because the pilot stays on. And one determines if the pilot is lit to allow the flame to light. Apparently, this sensor is not working.

I understand that there is a third sensor to determine if the chimney gas is too hot that is located at the top of the firebox, which also turns off the gas supply to the flame. This one could also be defective.

If the connection that determines that the flame is okay to light (the thermocouple?) is likely to be defective, then I will get one and get committed to replacing it. A Heatilator thermocouple appears on ebay for about $30 with shipping and shows as copper color. A thermopile is about $45. A whole Heatilator Direct Vent Fireplace Gas Pilot Assembly is about $80.

I am stuck at this point. What do you suggest?

 

[DAKSY]

When you turn the wall switch on, what is the millivolt reading of the thermopile?
It should drop to about 220mV & & hold steady.
If nothing happens, jump the two screws that are labelled TH & TH-TP (or TP-TH)
with a short piece of wire or a bent paper clip.
What happens then?

 

[JimDaugherty]

Thank you very much for your response. Tonight (after about 20 hours with gas shut off), I lit the pilot light and did other things for about 45 minutes with only the pilot light. At that time, terminals TH/TP and TP read about .672 and were fairly steady. When I turned on the wall switch, the flame ignited immediately, just like it should. The TH/TP and TP readings bounce around .300 to .400, over the course of about minute. Testing again after about 10 minutes of flame on, the reading rises from about .390 to .410 over the course of 30 seconds. I turned the wall switch off and flame goes out. After about 5 minutes of flame out, a check of the terminals TH/TP and TP read about .675 rising to .680 over about 30 seconds. I waited about 15 minutes, turn the wall switch on and have a flame in the firebox. I let it burn about 5 minutes and turn it out for about 30 minutes. Then flame turns on again like it should with the wall switch turned on.

I am happy that the gas fireplace appears to work correctly now but I am frustrated that it isn't reliable. Because the flame worked tonight as it should, I didn't use the jumpers to see what happened.

I will leave the pilot on and see how it works after days of pilot light on. I won't be able to tinker with the fireplace until this Thursday (at the earliest, next Sunday at the latest) due to my day job. If you have additional diagnostics or conclusions, I look forward to hearing from you then. Thank you again.

 

[DAKSY]

Thank you very much for your response. Tonight (after about 20 hours with gas shut off), I lit the pilot light and did other things for about 45 minutes with only the pilot light. At that time, terminals TH/TP and TP read about .672 and were fairly steady. When I turned on the wall switch, the flame ignited immediately, just like it should. The TH/TP and TP readings bounce around .300 to .400, over the course of about minute. Testing again after about 10 minutes of flame on, the reading rises from about .390 to .410 over the course of 30 seconds. I turned the wall switch off and flame goes out. After about 5 minutes of flame out, a check of the terminals TH/TP and TP read about .675 rising to .680 over about 30 seconds. I waited about 15 minutes, turn the wall switch on and have a flame in the firebox. I let it burn about 5 minutes and turn it out for about 30 minutes. Then flame turns on again like it should with the wall switch turned on.

I am happy that the gas fireplace appears to work correctly now but I am frustrated that it isn't reliable. Because the flame worked tonight as it should, I didn't use the jumpers to see what happened.

I will leave the pilot on and see how it works after days of pilot light on. I won't be able to tinker with the fireplace until this Thursday (at the earliest, next Sunday at the latest) due to my day job. If you have additional diagnostics or conclusions, I look forward to hearing from you then. Thank you again.

I would adjust the pilot down about 100mV. I know it's a 750mV Thermopile,
& 672mV isn't way high, but too much pilot flame will eat them up.
I like to keep them around 550mV.
The reason I asked you to jump the terminals was to rule out the wall switch.
Even though it's a millivolt system, the switch can fail, & it can fail during operation.
Sporadic outages can be a sign of a faulty switch.

 

[JimDaugherty]

After having the pilot on for about 26 hours, I flipped the wall switch and the flames appeared immediately. I didn't know how to “adjust the pilot down about 100mV.” The control valve has a stamping “PILOT ADJ.” I went to YouTube and found a video of “How to adjust furnace pilot light,” which has a similar gas control valve.

I took out the cover screw above “PILOT ADJ” and tightened (righty tighty) the inner screw until the pilot light is noticeably smaller. I replaced the cover screw, did a leak check (brush on soapy water and look for bubbles-none noted) and turned the gas supply line off for everything to cool down.

After bout 7-10 minutes, I checked terminals TH/TP and TP read about .350. I turned on the gas, the pilot lighted with one push. I waited about 5 minutes, the terminals TH/TP and TP read about .545 to .548 over the course of about 30 seconds. I flipped the wall switch, the flame turns on again like it should.

I now suspect that the wall switch contacts were not in good shape (after a summer of no activity) and several throws of the wall switch have improved the electrical contact. The fireplace seems okay now. Other than vacuumed the cobwebs out of the firebox and around the controls under it, I have really done nothing. I may not be able to verify my “wall switch” hypothesis until next year. Now I know how to test the wall switch using jumpers.

The nearest Heatilator service location is about 30 miles away. A service call, if available, would have been pricy. Thank you. You have been fabulous help.

 

[DAKSY]

FWIW, you can also test the switch by pulling it from the wall &
removing the wires. Touch the ends together (close the switch).
If the unit comes on it's the switch.
Glad you're up & running.