how to get a pilot light to stay lit on a furnace?

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Postby Ratkity » Thu Nov 03, 2011 11:26 am

I have found that the thermacouple can be bent too far away from the pilot in order to stay lit. Some need a little tweaking to be closer to it.

Hugs,
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Postby Ratkity » Thu Nov 03, 2011 2:02 pm

slowcowboy wrote:hey, thanks ratkitty. just a queston though. how far should a termocuple be from a pilot lite?

would like any more suggestions and impot on this topic. just in case this does not cure it.

slow.


Someone with more furnace experience can tell you. I had the same problem with both furnace and propane hot water heater on an old popup and fixed it by bending both the thermocoupler a tiny bit towards the pilot light outlet. It wasn't a lot of bend.

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Postby len19070 » Thu Nov 03, 2011 2:17 pm

Not knowing what unit you have????

IF! you have to push, or turn a Pilot button in to get it lit. And it stays lit while the button is in. But the moment you release the button and it goes out. It may remotely be the thermocouple...But is most likely a Gas valve.

To test this hold a butane lighter on the thermocouple constantly. If it remains on when the button is released, then the thermocouple is out of adjustment.... Adjust it and Make it work!

If this does not work then you need a Gas valve.

Another trick is to remove the thermocouple from the gas valve, clean it at the fitting and reinstall it. (dirt, #1 cause of ALL problems)

The sequence of operation on "Most" furnaces" is....

The Red Man Swims Like Big Green Iguana.

The...thermostat
Red...Relay
Man...Motor
Swims...Sail switch
Like...Limit Switch
Big...Board
Green...Gas Valve
Iguana...Ignitor

Hope this helps.

BTW, check the obvious things too (don't mean to insult you) Gas, 12 volt, big clumps of dirt on the burner....etc

Happy Trails

Len
Last edited by len19070 on Fri Nov 04, 2011 6:17 am, edited 1 time in total.
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Postby aggie79 » Thu Nov 03, 2011 3:49 pm

Hey Slow,

Don't mean to hijack the thread, but I just talked with a guy I went to school with that I haven't heard from in 31 years. He lives on a ranch outside of Thermopolis. We're trying to arrange a trip to meet - maybe in Casper.

Good luck with your heater.

Take care,
Tom
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Postby Mightydog » Thu Nov 03, 2011 4:42 pm

len19070 wrote:dirt, #1 cause of ALL problems


...and many good times!
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Postby TOTAL CARNAGE » Thu Nov 03, 2011 8:23 pm

It can only be the the thermocouple or less likely the gas valve it's self.
The pilot light on older furnaces will burn with the power and thermostat disconnected! The only control on it is the thermocouple.......
It should be like half way into the pilot light flame and should glow red when adjusted right.
If after cleaning, new thermocouple and adjusting it still won't work then the little valve in the block is stuck. That's one thing I don't trust doing myself so I can't tell you just what is in there. I just got a new one.
I have a very old pain in the.........in my motor home and I have to hold that button down for a very long time before the thermocouple is hot enough to keep the pilot lit. Good luck and BE CAREFUL!
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Postby Dale M. » Thu Nov 03, 2011 9:34 pm

Basically all the thermal couples I have seen have actually been IN the pilot light flame...... Problem may be its to far a way there for to cool....

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Postby Moho » Thu Nov 03, 2011 11:38 pm

The thermocouple should be in the flame in order for the two different metals in the thermocouple to produce voltage.

Also make sure the pilot has a strong flame. Carbon can build up in the pilot orifice and make the flame not be strong enough to heat the thermocouple up enough. I have also seen the carbon cause the flame to split and the flame will actually blow on each side of the thremocouple and not directly on it. Usually a couple of sharp taps with a pair of pliers on the pilot is enough to break loose any carbon build up.

Lastly some older unit require you hold down the pilot button on the gas valve for 30 seconds or so.

If all the above fails then most likely the magnet in the gas valve is the problem and the gas valve will need replaced.
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Postby Kevin & Sandy » Fri Nov 04, 2011 1:18 pm

I have a propane radiant heater in my garage. The tip of the thermocouple is in the flame, but it takes some real patience holding the switch down in the "pilot" position because it takes a long time to heat the thermocouple enough. It may be a minute or two, it seems like an hours when you have cold fingers and you are up on a ladder holding the switch.
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TC Tricks

Postby Engineer Guy » Fri Nov 04, 2011 1:40 pm

Some other lil tweaks I've learned when graduating from 'The School Of Hard Knocks' are these:

1. It's somewhat counterintuitive, but there's hotter and cooler parts of a Flame. Ideally, it should be burning 'all blue' and not yellow. All blue indicates the right Air/Gas mixture, and that varies at - ta da - higher elevations like WY. There's usually a small Screw or 'slide' type adjustment to vary Air/Gas to make the Flame 'more ideal' [blue].

Also, slide the Thermocouple [TC] back-and-forth laterally in the lil Holder Clamp to ensure hitting the TC 'sweet spot' internally. I shoot for the halfway point of the TC, or ~2/3rds of way away from the base 'Wire' connecting it to the Gas Valve.

2. One of the hottest parts of a Flame is just above the inner oblong Flame, just below the Flame top. If the TC can be adjusted JUST above that Flame section, the increased heat outputs more milliVoltage, which is what's signaling the Gas Valve to stay open.

3. Where the TC screws into the Gas Valve, there's typically a lil half-dome 'blob' of Solder-looking material on that 'Wire' end. Clean that with a Pencil Eraser, etc., to scuff it clean. REALLY crank down on that lil piece when putting it back together to ensure a good connection is made. Obviously, the correct torque is short of breaking anything!

4. I always hold in the Gas Valve Knob for a minimum of 1 minute after lighting to ensure the TC is outputting max. milliVoltage. You're thus giving it the best chance to 'succeed'.

Part of Troubleshooting is learning what a problem 'isn't'. If you can do these tricks above, and things still don't work as desired, you know to move on with confidence to troubleshoot other possibilities because you know what it's 'not'.

My lil TT Dometic Fridge Flame was acting up at 8,300' in UT. I KNEW all was OK. Anyway, I cleaned up all surfaces with 'Scotch Brite', yadda, yadda yadda. FINALLY, I grasped at Straws and took off a lil Housing Cover around the Flame, and propped open the outside Fridge Hatch with a Twig. Ta da, the Fridge Flame stayed lit. The problem: insufficient Oxygen @ 8,300', causing the Flame to go out after ~1 minute. It was frustrating because the Flame would stay on 'for a while', then 'puff' out audibly.

I vaguely recall that Leadville CO has ~20% less Atmosphere at their ~10,000 elevation, and it popped into my Head that elevation/less Air was the Fridge Flame problem. It had worked that morning at ~6,100', but not at ~8,300' that afternoon.

The concepts above are simplified to get to the point and not beat Theory to death... Another Lifelong trick of mine is to solve a problem and then go back to theorize what was going on, and what fixed a given problem.
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