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Furnace Acting Weird


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OK, this is odd, at least to me. It's been cold so the furnace has been running at night. Two nights ago I woke up because it was getting chilly. The furnace fan was running but no heat.

Obviously the sparker either wasn't firing, or the gas valve had gone bad. So, I got out my little Coleman catalytic heater, fired it up, and went back to sleep, figuring I would troubleshoot in the morning.

When I got up I made some coffee and decided to start the furnace again to see if I could get an idea of what was happening. Fan started and a few seconds later, CLICK goes the sparker and the damn thing fires right up and starts putting out heat, like it never had a problem. I take the facia off, turn it on and off a few times, observe that the piezo-type sparker is working and that its getting LP, and wonder WTF? It's firing up like it never had a problem.

Fast forward to last night. I turned on the furnace, went to sleep, and again, I wake up in the middle of the night because its chilly and the furnace is just blowing cold air. I get up, shut it off, turn it back on, and everything kicks on and I have heat. Again, WTF?

Anybody have any idea? I first thought it would be a breaker to the piezo tripping, but I would have to reset it, unless it has an internal of some type, which I doubt. Only other thing I can figure is maybe a draft disrupts the lighting of the burner, maybe because it was windy outside? That doesn't make a whole lot of sense either though. It has to be the gas valve sticking or something, right?

Anybody run across this before?

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Either that or the sail switch isn't quite making it.

Check outside, look up inside the intake and exhaust and make sure they are not partially blocked with leaves or bugs.

Normally, the furnace makes one attempt to light, if it fails, the blower keeps running.

John Mc

88 Dolphin 4 Auto

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My guess igniter board. They will only try once then give up and blow cold air. Dinosaur boards, good stuff they try 3 times and they have an optional board that will turn the fan off if it doesn't light. In the fact it started for you later with out doing any thing else kind of leads to a spark failure.

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Either that or the sail switch isn't quite making it.

Check outside, look up inside the intake and exhaust and make sure they are not partially blocked with leaves or bugs.

Normally, the furnace makes one attempt to light, if it fails, the blower keeps running.

John Mc

88 Dolphin 4 Auto

After further perusal of the boards, I saw that this seems to be a semi-common problem. Most of them prescribe cleaning the intake/exhaust, like you said. Sounds like this weekend's project to me, Thanks John.

My guess igniter board. They will only try once then give up and blow cold air. Dinosaur boards, good stuff they try 3 times and they have an optional board that will turn the fan off if it doesn't light. In the fact it started for you later with out doing any thing else kind of leads to a spark failure.

So, if that's the case, can I retrofit the dino-board to my unit? I suppose a little more info, like what model furnace I have would make it easier to answer, so I'll get that once daylight finally shows up. Thanks Maineah.

Cold weather will make a low battery even lower in power. When it warms up you get some of that power back. I remember from other discussions that when the battery is low the fan blows but the burner won't light. You might want to check your battery and see if it is in prime condition at bed time.

I actually thought this might be the case when it first happened. I checked the battery though and she's stronger than rent. Apparently the alternator on the vehicle can charge house batteries a lot faster than my old Class B could. With my old unit, If my batteries were dead, it would sometimes take four hours or so of driving to charge her up.

It seems the house battery on the Toy can fully charge after just a five or ten minute drive to the store. I wonder if the solenoid-type battery isolator has something to do with that. I had one of those blue-box, solid state isos on my old one and I didn't like that thing at all. It failed me more than once. Thanks Karin.

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Yes they make boards for stuff that is obsolete. There are a couple of things you'll need to know when ordering so have a look on line with your module numbers in hand. Mine did the same thing most of the time it lit but when you needed it the most it didn't. Dinosaur makes very nice boards for several applications including generator boards it's really quality stuff. I don't know why but a furnace with no fire makes a really good A/C!

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Yes they make boards for stuff that is obsolete. There are a couple of things you'll need to know when ordering so have a look on line with your module numbers in hand. Mine did the same thing most of the time it lit but when you needed it the most it didn't. Dinosaur makes very nice boards for several applications including generator boards it's really quality stuff. I don't know why but a furnace with no fire makes a really good A/C!

Did yours work after a reboot (turning it off/on)? That's what mine does. I just have to flick the switch back and forth and next time it cycles on I have heat.

I have a busy morning but when I get settled I'm going to take the whole thing apart and clean all the contacts, as well as the intake and exhaust. I have a feeling that might do it, since the furnace gave me no problems last night. It seems to be an intermittent thing, which probably means a loose or dirty connection somewhere. If not I'll look into this board thing. Thanks man.

One more thing: Do these suburban stats have an anticipator on them? My unit seems to cycle on and off just a bit too much. I used to know how to set one, but that was like a million years ago.

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Yes they do have an anticipator but it is no where as wide as it should be some thing like 2.5 degrees. The MH loses too much heat and they cycle often I agree with that, you set it down and it still cools off just as fast and the trend starts all over again. Yes If I started the heater again it fired right up 95% of the time the only time it didn't was when I needed it the most. Then you have to get up find the inside temp around -5 and the damn heater is blowing a winter nor'easter right on your feet.

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Well that makes sense, since this thing has about as much insulation as a chicken egg. I cleaned out the intake/exhaust today, and we shall see if that fixes the problem. It will be warm tonight so it may be a day or two until I figure out if that did the trick.

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VERY common problem. Mine does EXACT same thing. recommend cleaning intakes and use some parts cleaner on the sparker as well as clean burn chamber. and anything else that has dust bunnies. It will still have the problem even after all this just less.

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An older fan motor and a small drop in the 12v will cause this. The fan isn't running fast enough to trip the sail switch. Trouble by cycling the thermostat a couple of time and make sure it doesn't light. Then start the truck engine and see what happens, the 14v from the truck will turn the fan faster.

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An older fan motor and a small drop in the 12v will cause this. The fan isn't running fast enough to trip the sail switch. Trouble by cycling the thermostat a couple of time and make sure it doesn't light. Then start the truck engine and see what happens, the 14v from the truck will turn the fan faster.

You know, I have noticed a drag on the furnace blower when I turn on a light or something else, which makes me wonder if one or the other are pulling too many amps. This is happening on shore power, so unless I'm getting less than 30a off the post, something may be wrong. Of course this could be completely normal and I don't know that. I don't ever remember this happening in my old unit, so I just don't know.

As far as the sail switch goes, this blower, when running at full power, blows hard and loud. If anything it would be a sticky switch, but it would have to be really sticky, since this thing puts out a lot of wind, whether its cold or hot.

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Mine will end up blowing cold if the battery goes down even a little. I run the engine to top off the battery before going to bed and use very few lights. I am switching to LED's asap.

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Well, everything seems to check out. Maybe it is the battery. There is only a deep-cell 12v in the compartment, obviously a replacement. It's strong, but I probably need to get some 6v units lined up in there.

I'm on shore power for the time being, so I'll just make a note to check it next time I boondock.

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If its the low motor rpm thing, you shouldn't have any problems on shore power

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