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Please help with old furnace

tadmintadmin Posts: 3Member
I have an old original Coleman furnace, 1986 vintage, and the pilot light keeps going out, rather randomly.

I've had the local heating company out to look at it twice and they are stumped. It has been fine for the last 10 years, then it started acting up about a year or so ago.

Thermocouple has been replaced twice. Once lit I can remove my thumb immediately from the black button you depress to light the pilot and it stays lit. Always stays lit upon lifting.

Thought for sure might be the roof vent / cap as the pilot seems to dance around some when I hear the wind howl, but I don't think so. Recently we had an extremely gusty day with winds > 20 MPH and it didn't go out. Been lit for almost a week. It was out this morning tho.

From my own observations it seems to go out as the thermostat calls for heat, but not always. I asked heating guy to check the pilot light gas pressure, and I watched him do it. He said it was fine. If I recall correctly it was 14 inches of mercury.

So weird.

Any chance the problem could be the main gas valve (that the thermocouple screws into)?

When the furnace kicks on it made a howling noise for a short while (30 seconds to a minute roughly). There is a rod that the heating company says controls the air intake. He made an adjustment to that, watching the flame thru the burn window to what he thought was a good quality blue flame, and that howling went away. I actually think the pilot goes out more now than before, but actually its so random (it can go for days, but sometimes I'll wake up to a cold house after lighting it the previous day) its hard to say for sure. It stayed lit all summer long this year, didn't need to light it.

I live in a 1986 mobile home, and can't afford the cost to replace the heating. I'm quite the do it yourself kindof person and thought about trying to retrofit an electronic igniter to replace the pilot, but aside from the safety concerns it would be tough on such an old system.

Any input on things to check or suggestions are welcome.



  • HVACNUTHVACNUT Posts: 2,047Member
    If nobody did a combustion test, checked for a cracked heat exchanger and carbon monoxide, then it's time to call a different heating contractor.
    Do you have a carbon monoxide alarm?
  • ratioratio Posts: 1,936Member
    HVACNUT said:

    If nobody did a combustion test, checked for a cracked heat exchanger and carbon monoxide, then it's time to call a different heating contractor.

    Do you have a carbon monoxide alarm?

    At over 30 years old, it's lived twice the lifetime I generally see. At the very least, you must have it examined carefully & tested with a modern digital combustion analyzer to see if it has faults that will release deadly carbon monoxide into your house.

    I know you don't want to hear this, but it's time to budget for a new one. Even if this one is still safe to operate, it's running on borrowed time.

    Do get a CO alarm, & understand that if it sounds you've already been poisoned & should call the fire department.

  • IronmanIronman Posts: 4,970Member
    It’s more than likely that you have a cracked heat exchanger and when the blower kicks on, it’s blowing out the pilot. That’s a very serious condition which could cause CO poisoning for you and your family.

    As others have noted, the furnace is at twice it’s life expectancy and replacement is maybe your only reasonable course of action.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Solid_Fuel_ManSolid_Fuel_Man Posts: 1,458Member
    Not to mention a newer unit will save you gas in the long run. So that savings may help justify the cost.
    Master electrician specialising in boiler and burner controls, multiple fuel systems, radiant system controls, building controls, and universal refrigeration tech.
  • tadmintadmin Posts: 3Member
    @hvacnut, you make a very good point about evaluating combustion. I'll check and see if my local company can do that.

    @ratio, sure it's old, but not only can't afford it, I'm also opposed to the very prevalent consumerism, product churning pushed by corporations and most businesses these days. I like the adage, if it's not broke don't "fix" it.

    I have 2 carbon monoxide detectors, and a wood stove as well, so I don't feel I'm taking undue risks.

    In terms of replacement (assuming combustion is good and no leaks) that saying is apropos. The pilot issue may be an indication of some other fault that may be serious enough to warrant replacement, but if so I would simply opt to use the wood stove exclusively for primary heat, and perhaps install a small ventless propane heater to keep the pipes from freezing when I travel.

    Thank you everyone for your comments, I'm very grateful for them all.
  • DZoroDZoro Posts: 752Member
    That was all good advise, and would be wise to do as advised.
    Do not install a ventless heater, under no circumstances, even when gone I wouldn't have one running in a home.
    Most gas companies will shut you down if found on inspection.
    Wall vented ones are only a few dollars more.

  • nibsnibs Posts: 215Member
    Have found that the pilot jet can partially plug up, if you can get at it, try taking it out & soaking it in acetone or other powerful solvent, blow it out and see if that helps. I have some very fine drill bits bought so that I could make my own pilot for a custom burner, I have used them to clean the pilot, pushing in by hand, as a broach, not a drill bit do not try drilling, you will wreck the tip.
  • tadmintadmin Posts: 3Member
    @DZoro, thx for that info. There are tons of people around here that use the ventless heaters. Still many models available new in stores.

    Nevertheless, I too would prefer something vented, and if I go that route will research to find a suitable vented model.

    @nibs, that is a great suggestion. I have a range of extremely small bits for drilling circuit boards and cleaning carb orafices. Worth a check.

    Should the pilot burn yellow or blue? It burns yellow now.
  • Jamie HallJamie Hall Posts: 10,293Member
    Quite true. There are lots of people who use ventless heaters. That doesn't make them safe. I know of no code, not any manufacturer, which allows the use of a ventless heater in a living space. Low level CO poisoning is no joke.

    To which end, may I add that you may have a CO detector -- but does it alarm at a low level? Many CO detectors don't do anything until the level reaches around 100 ppm. In my humble opinion -- backed by OSHA -- that's too high. The OSHA limit for general exposure is 50 ppm. If you have one that alarms at of above 100, regard it this way: if it sounds off, it's past time to evacuate the premises and call the fire department...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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