Gas Fireplace Troubleshooting

[dan3710]

I have a Majestic Natural Gas fireplace (36BDVR) which is approximately 10 years old. It has been operating without any problems until the last week or so. I can light the pilot without any problems but getting the main burner to light and stay lit is the problem. I can get about 320 mv out of the thermopile and when I close the switch the burner comes on then the output gradually drops to about 130 mv where everything cuts off. Any ideas? It seems to me the thermopile is good, would this be indicative of a bad thermocouple?

Other information, blue flame from the pilot touches the thermopile approximately 1/2" from the tip.

I tried a few searches on various sites with no luck so far.

[dan3710]

A few additions to help with troubleshooting:

There is about 3 feet from the thermopile to the control unit, and then an additional 10 feet of wire to the wall switch.

[paul52446m]

Gas Fireplace Troubleshooting

I have a Majestic Natural Gas fireplace (36BDVR) which is approximately 10 years old. It has been operating without any problems until the last week or so. I can light the pilot without any problems but getting the main burner to light and stay lit is the problem. I can get about 320 mv out of the thermopile and when I close the switch the burner comes on then the output gradually drops to about 130 mv where everything cuts off. Any ideas? It seems to me the thermopile is good, would this be indicative of a bad thermocouple?

Other information, blue flame from the pilot touches the thermopile approximately 1/2" from the tip.

I tried a few searches on various sites with no luck so far.

I don't what power pile you have, but if you take off all wires except the two going to the power pile. then test it. If its a 750 MV then you should get 700 or more at this test, with a good pilot and good power pile.
Its real easy to lose power on a mv system so make sure all wires are clean. and tight. You can take the wires off that go to the stat and jump them out at the gas valve and see if you keep your power.. How long is your stat wire?
You could also have a gas valve pulling too much power. Paul

[kalicocat]

dan!

...paul is absolutely on the right track! ...750 mv is optimum, but realistically the unit should 'theoretically' run correctly on 325-375mv...there are a few things that can contribute to the prob, but a couple are usually the culprit, and the other two less common issues...you did mention a thermocouple, correct? is the tip of the couple intact, or is it 'burnt off' & rough @ the tip?...reason being, the couple is what holds the pilot, the pile holds the main; they are in fact two 'independent' systems...when u say the entire 'operation' shuts off, do u mean to say that u must 'start from scratch' and manually relight the pilot again each time u try, and this happens as well?...if the t-Couple looks good, and if the t-Pile is putting out correct voltage (within reason) then it is prolly an entirely 'unconventional' problem of sorts...the simplest would be to replace the pile w/ a new one, but 1st, make sure it is actually 'dead' even though it is apparently putting out the voltages u need 2 operate the unit...its ez...pilot lit, valve to 'on' position, all ready 2 go but dont 'throw the switch'...take a jumper wire (paperclip is much quicker!) and literally jump the connection between TP and TP DIRECTLY on the control valve head (where ur T-stat and/or wallswitch connections attach!), the main should come on & hold steady!...if it does NOT, then the issue is prolly a bad t-Pile (the pilot should still not go out in this situation, though!)...BUT...if it does come on & hold steady, then it is prolly a 'non conventional prob in ur wiring; too much resistance or bad connection, corrosion, whatever...u gotta figure this is LESS than 1volt dc being generated, ran thru teenytiny bell-wire for 10 feet to a switch, THEN thru the switch itself, AND 10 more feet back, THEN operate the coils inside the valve to open the main operator!!! thats ALOT of work for LESS than 1 volt!

if this doesnt reveal something outright, then we can move to the less obvious 'non-conventional' issues!

hope it helps!
-deano

[dan3710]

Sorry, it has been a long week. I just got a chance to look into it a little more. So after taking out all the logs, the tip of both the thermopile and thermocouple are smooth and clean. The pilot light itself starts up no problem and the thermopile puts out approximately 107mv at the start and slowly moves up to 248mv after a minute or so. The pilot is strong but there is aparentally a small leak because a secondary flame intermittantly appeared at the base of the pilot light. Once the voltage got above 250 I was able to throw the switch / jump the terminals and the main burner came on. Once the burner came on the pilot light decreased in size and the thermopile output slowly decreased to 134mv where both the main burner and the pilot went out. The leads from the thermo pile and thermocouple have clean connections and are less than 1 foot in lenght. Thoughts?

[paul52446m]

» Gas Fireplace Troubleshooting

Sorry, it has been a long week. I just got a chance to look into it a little more. So after taking out all the logs, the tip of both the thermopile and thermocouple are smooth and clean. The pilot light itself starts up no problem and the thermopile puts out approximately 107mv at the start and slowly moves up to 248mv after a minute or so. The pilot is strong but there is aparentally a small leak because a secondary flame intermittantly appeared at the base of the pilot light. Once the voltage got above 250 I was able to throw the switch / jump the terminals and the main burner came on. Once the burner came on the pilot light decreased in size and the thermopile output slowly decreased to 134mv where both the main burner and the pilot went out. The leads from the thermo pile and thermocouple have clean connections and are less than 1 foot in lenght. Thoughts?

You have a leak in the pilot line connection so main burner is lighting it off so you lose some of you pilot flame. Take pilot apart, clean out good. tighten all fitting. make sure both power pile and thermocouple are all the way up in place. Like i said before a good sharp blue flame has to go all the way around them. Do you know what power pile you put in there. it should be a 700.
Some of the gas valves take 240 MV to keep the open. Paul

[dan3710]

It is a 700mv pile. So I can see the flame intermittentaly comes out of the oriface beneath the burner, where the air joins the gas before it is lit. Also, this is probably a pretty new guy question, but what is the best way to clean out the pilot? Can I soak it in something or will a wire brush do the trick?

[paul52446m]

Gas Fireplace Troubleshooting

It is a 700mv pile. So I can see the flame intermittentaly comes out of the oriface beneath the burner, where the air joins the gas before it is lit. Also, this is probably a pretty new guy question, but what is the best way to clean out the pilot? Can I soak it in something or will a wire brush do the trick?

If there is a heating supply house around you, you can pick up a broach to clean the orifice. The pilot line unscrews from the pilot . You can blow out the pilot.
The orifice hole is very small and you don't want to make it larger The broach goes from 1/8" down to very small so you can ream out the hole with out drilling it. Paul

[kalicocat]

dan...

ditto the long week...taking classes to find my way back into the workforce as has not been the case lately!

...you say..." Once the burner came on the pilot light decreased in size and the thermopile output slowly decreased to 134mv where both the main burner and the pilot went out. "

did the main burner flame ALSO decrease @ all, or stay 'robust & normal' only the pilot flame decreasing in output?

when the pilot flame decreases, is it progressively 'shrinking' till nothing...or does it jus' get smaller, stay smaller, & slowly lose voltage on the T-couple/T-pile, which eventually cuts out the pilot/main?

If you are in the 'middle' of this 'failure operation', can you unswitch/cut out the main...and does the pilot return to its 'normal' self? pilot remain on, control valve does NOT kill pilot w/ this specific (interrupting of main) action?

[kalicocat]

...pressures?

Dan...not sure where you're @ w/ this one so far, but when you say the pilot decreased when you engaged the main burner is a pretty peculiar thing, NOT common @ all...may be a long shot, but to me that's one of two major issues; one is related directly to pressures (or lack thereof!)...if you are running propane (LP), you may check your 2nd stage regulator (the one on the house where it comes in...1st stage is usually on the tank itself) & have it tested/set up to correct pressures (11-13WC) or possibly replaced...they don't go bad often, but sometimes they fail, especially if they get water in the vent...there is a very remote possibility of blockage itself in the fireplace supply/main/pilot lines, but again, VERY remote...second, the problem may be, as much as i hate to think, the control valve itself has went TU ...and these also fail VERY rarely, but they do fail on occasion as well...curious to know your status/outcome so far!...they are fairly 'simple' devices in operation & theory, but not so easy to diagnose sometimes when inop...very frustrating for sure!