Shop Furnace pilot light going out

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BobReeves

Member

• Dec 24, 2017

• #1

I'm having an issue with the furnace in my shop and when it's cold I may not go out there for several days at a time. Once in a while the pilot light in the furnace will go out, thermostat is telling the furnace to turn on the heat which turns on the blower but with the pilot out it never warms up the shop enough to turn the furnace off. The result is I find the shop at 30 deg with the furnace fan running when the thermostat is set for 50. Have to keep some heat going to keep the water lines from freezing.

It always lights and stays lit really easy which tells me the thermocouple is probably good. Not real sure why it goes out, seems to be random and not associated with the wind speed. It is an old furnace/shop heater but still works well when the pilot stays lit. Probably should also add it is on a propane tank shared with the house but can't imagine that making any difference

Any ideas on what would cause the pilot to go out, maybe a mouse blowing it out because he is getting too warm.

 

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RBoots

Well-known Member

• Dec 24, 2017

• #1

Sometimes a cracked heat exchanger will put
a pilot out

 

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John730D

Well-known Member

• Dec 24, 2017

• #1

I had the same problem last year. Found spider web in pilot light. Cleaned it out and have not had any problems since.

 

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rrc300 u

Member

• Dec 24, 2017

• #1

Takeout That pilot assembly and blow
it out with compressed air. Especially
on propane they will get dirty, the
oulit will still light but when the
unit has run for a long time the draft
will pull the pilot flame away from
the thermocouple. This will let it
cool off and not make enough
millivolts to keep the pilot valve
open. This the pilot how's out

 

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Determined

Well-known Member

• Dec 24, 2017

• #1

Pilot flame low?
Maybe need clean and adjust.
Thermocouple not expensive and fairly easy to replace, I have had them act like you describe, replacement solved the problem.

 

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ray hofstetter

Well-known Member

• Dec 24, 2017

• #1

Had the same problem, but replaced the
thermocouple and have never had a problem
since. I always thought they just quit
working, never saw one do the intermittent
thing...learned something new.

 

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ed will

Well-known Member

• Dec 24, 2017

• #1

I had that problem with the furnace pilot light in our
r/v. Changed the thermocouple and it was fine. I
think it was about $10. And easy to change. As
others say try cleaning first or adjust the flame to
hit the thermocouple better. It has to generate
enough milliamps to open main gas valve.
Ed Will. Merry Christmas.

 

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da.bees

Well-known Member

• Dec 24, 2017

• #1

If all the shots into dark fail,post back and we can go through test process using a vom.

 

Goose

Well-known Member

• Dec 24, 2017

• #1

You might clean the orifice in the pilot. I had the same problem a couple of years ago in my shop. The pilot flame was plenty strong, but it was yellowish and not hot enough to keep the thermocouple set.

Ran the right size acetylene welder tip cleaning wire through the pilot orifice and it works fine. Flame's blue again, also.

 

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fixerupper

Well-known Member

• Dec 24, 2017

• #1

Like the others said it sounds like the pilot is getting weak.

 

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jCarroll

Well-known Member

Location

mid-Ohio

• Dec 24, 2017

• #1

I had Goose's situation ........
Propane pilot was iffy to keep valve "on"

The orifice at the end of the pilot light gas line had a little CRUD on it.
I cleaned it with an awl and a tiny wire.

Worked OK now for 2 months.

 

O

OldFarmTractor

Member

• Dec 24, 2017

• #1

Let's see, you are ending up with a cold shop.

It might be the thermocouple or the pilot or both.

You are either on a ladder or laying on the ground for this repair.

A NEW thermocouple is $5.32 at Home Depot.

I think I would clean the orifice on the pilot and replace the thermocouple. Why be cold?
Thermocouple Home Depot

 

K

Kansasredneck

Member

• Dec 24, 2017

• #1

1. The gas creates a residue as it burns which can plug the pilot orifice. try using a pin to clean the end.
2. Check that the flame is enough to keep the thermocouple warm. might need to adjust it a little.
3. If the heat exchanger is cracked, that will put out the pilot when the fan kicks in.

 

casecollectorsc

Well-known Member

Location

E central SD.

• Dec 24, 2017

• #1

Need a like button...I clean mine at the beginning of each heating season.

 

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Steve@Advance

Well-known Member

• Dec 24, 2017

• #1

First thing I would check is the heat exchanger.

Watch the pilot and flame as it cycles on. If the pilot or flame blows around, gets drawn up off the
burner, or tries to blow out, chances are there is a crack or hole burned/rusted through the exchanger.

If that has happened, time to retire it! Not only is it a fire hazard, it will leak carbon monoxide into
the room.

If the exchanger checks out, like others have said, be sure there is sufficient heat getting to the
thermocoupler. One word of caution, if you take the pilot assembly out for cleaning, don't enlarge the
pilot jet while cleaning it! The hole is so tiny, running anything through it will result it the pilot
burning too large, wasting gas, overheating the thermocoupler.

I have converted several over to intermittent pilot with this kit. Works well, no more pilot problems.
Intermittent Pilot Kit

 

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jeffcat

Well-known Member

• Dec 24, 2017

• #1

One simple thing is take a look at the flame. It should be a nice
clean blue flame . Maybe 3/4 of an inch long and nicely surround the
end of the thermal couple. You could have a big fuzz bunny in the air
channel. Blow it out with your air chuck. Replace the therman couple
anyhow cause they are cheep and get weak. That should do it.

 

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JD Seller

Well-known Member

• Dec 24, 2017

• #1

I will second or third, LOL cleaning the pilot light orifice and wiping the thermocouple off. I have several wall gas wall heaters. I have to clean them annually or they will do what yours is doing.

 

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B

BobReeves

Member

• Dec 25, 2017

• #1

Thanks a million gang, will grab a new thermocouple tomorrow, doubt I could find one today. I replaced it a couple years ago but one never knows. Will also check the pilot flame as suggested.

The retrofit kit is sure interesting, wasn't aware they existed. I had to replace the gas valve 4 or 5 years ago, wished I had known about that kit back then. Sure something to think about.

(quoted from post at 13:52:18 12/24/17) First thing I would check is the heat exchanger.

Watch the pilot and flame as it cycles on. If the pilot or flame blows around, gets drawn up off the
burner, or tries to blow out, chances are there is a crack or hole burned/rusted through the exchanger.

If that has happened, time to retire it! Not only is it a fire hazard, it will leak carbon monoxide into
the room.

If the exchanger checks out, like others have said, be sure there is sufficient heat getting to the
thermocoupler. One word of caution, if you take the pilot assembly out for cleaning, don't enlarge the
pilot jet while cleaning it! The hole is so tiny, running anything through it will result it the pilot
burning too large, wasting gas, overheating the thermocoupler.

I have converted several over to intermittent pilot with this kit. Works well, no more pilot problems.
Intermittent Pilot Kit

Click to expand...

 

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rubberwrench

Member

• Dec 25, 2017

• #1

check for back draft in chimney when conditions are right. May need power vent or wind block have seen this twice on two different heaters.

 

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BobReeves

Member

• Dec 25, 2017

• #1

Couple more questions...

Could the thermocouple get damaged over time if the pilot is set too high? If so that might be the case, the pilot is two flames each being about 2 inches high. One is pointed at the thermocouple, the other lights the furnace. The base is blue but the top 1/3 is orange.

Also, in looking at the retro fit kit on eBay I see a RobertShaw kit that is somewhat less money. Wondering if it would work as well as the Honeywell?

 

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BobReeves

Member

• Dec 25, 2017

• #1

Never mind question #2 above, found this on the RobertShaw web site. "Caution: Do not use on LP gas applications".

That pretty much eliminated the RS unit.

 

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Leroy

Well-known Member

• Dec 25, 2017

• #1

Not a furnace but a ventless wall heater. Had problems with pilot consatantly going out, even service man could not figure it out. Finally was going to replace the thermo couple and found it was just loose enough it had sliped down just enough the flame was not touching the end of the thermo couple. Was able to jusy loosen screw that holds it on and moved it back to where it was in the pilot and tightened and has been fine for a few years now. Getting cold enough I have to now lite that heater in that part of the house. I think just the draft from the furnace in rest of house was enough to affect the flame and blow it away from the couple.