Only 1/2 of pan burner is lighting

[hrbjr]

I have a Napoleon GD70 LP fireplace. I just replaced the pilot assembly because the pilot kept going out. The whole assembly was rusted so I figure I'd replace it.

After replacing and testing, only 1/2 the burner pan lights up. The entire back row and only the left side (side where gas enters) to the middle. Never extends from middle to the end of the right.

When I turn it off, about 2 seconds after the pilot goes out. This is a brand new pilot assembly.

I vacuumed the entire firebox, and blew out all oriface holes. No change to pan burner.

Suggestions? Thoughts?
Thanks

 

[DAKSY]

Have you verified gas pressure?

 

[hrbjr]

Than

Have you verified gas pressure?

Thanks for replying!

Don’t you need a special gauge for that? Also, I just changed out the pilot assembly so how could that effect the gas pressure?

 

[DAKSY]

Yes, you need a manometer to check inches of Water Column.
I would check it as a matter of course...
If it's low, there may not be enough gas to feed the entire
burner before it's consumed...
The reason your pilot may have been going out could be loose
debris in the gas line which may have traveled to the pilot.

 

[hrbjr]

How do you check the debris at the pilot and clear it?

 

[DAKSY]

Carefully disconnect the pilot tube from the valve & the pilot hood.
Blow thru it with compressed air. Do the same with the pilot orifice
which will drop from the pilot hood.

 

[hrbjr]

I disconnected the pilot tube, blew it out and blew out the pilot orifice. Pilot runs OK until you turn the fireplace out. After about a minute, when you turn off the fire place, the pilot blows out.

 

[DAKSY]

SO the pilot stays lit while the burner is on, but shuts down when the burner is shut off?
Does the pilot look strong? Is it encompassing the top 3/8" to 1/2 of the thermocouple?
Have you tried turning the pilot screw to adjust the pilot?
Have you taken a reading on the pilot with a multimeter?
Have you checked the thermocouple millivolts with a multimeter?

 

[hrbjr]

• #8

SO the pilot stays lit while the burner is on, but shuts down when the burner is shut off? - Correct
Does the pilot look strong? Is it encompassing the top 3/8" to 1/2 of the thermocouple? - Yes
Have you tried turning the pilot screw to adjust the pilot? - No
Have you taken a reading on the pilot with a multimeter? - Do you know what the reading should be?
Have you checked the thermocouple millivolts with a multimeter? - Do you know what the reading should be?

 

[DAKSY]

Reading the pilot at the TP & TP-TH connections should read 220 +/- 20 mV with the burner ON.
It should read 550 +/- 25mV at those same terminals with the burner OFF.
To read the thermocouple, You will need an extra pair of hands.
You need to disconnect the TC from the valve & with one probe on the copper wire
& the other on the very end (the little "button" that goes in the valve), you will need the pilot lit &
the On-Pilot-Off knob depressed to hold the flame. You should get above 28 mV.
If your readings are low, try turning the pilot adjustment screw & see if you can increase
the size of the flames. Your mV readings on the TP should increase.

 

[hrbjr]

I lit the pilot and it stayed running for 2 hours. I did the test with reading and the results are:

With the thermopile open, the reading was 530. With the burner on it was 250. When the burner was turned off the reading went to 460 and then the pilot went out.

Testing the thermocouple, the reading with the pilot lit and button depressed was 21. Turned the pilot higher for bigger flame rendered a reading of 22 and no higher.

 

[DAKSY]

Interesting. I'd say your TC is marginally functional.
I know you just replaced it with the pilot assembly,
but I'd say that's the culprit. Like I indicated earlier,
28+ mV is where it works best.
Unfortunately electrical parts can fail right out of the box...