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BryannasTreasureBox · 01-19-2005, 08:06 AM

Greetings,

I own a 1984 30' Winnebago Chieftain. Last winter I was having intermittant problems with the furnace, and had it and the thermostat replaced new. This winter the same problem, the furnace blows but doesn't click to light. This is intermittant and seems to be related to the outside temperature. When the outside temp is less than 20 the furnace blows only cold air. When the inside temp is less than 45, the furnace blows cold even when the thermostat is switched to 'off'. Yesterday the outside temp was 55-60 and the furnace ran fine.

Thinking it was a propane pressure problem, I switched to a new full 40# propane tank. I have a hose extension running to a portable tank. The stove, fridge, and oven all burn fine at these temperatures and hooking up the new tank didn't change anything. We are hooked up to 110 via an adapter, plugged into a standard electric outlet in the garage.

I'm on an Energy Assistance Program for low income and they contracted to have the new furnace installed last year. It was a general handyman type. He didn't do any diagnosing, just recommended replacement of the 20 year old furnace and the EAP paid for it. (I kept it for spare parts.)

A friend thinks there might be water vapor in the propane lines and it freezes. If so, how do I fix that?

The furnace say 'Suburban' and the installation paperwork I have says DynaTrail, instructions for models nt-24sp, nt-30sp, nt-34sp. I couldn't find a model number printed on the furnace itself. did find a dead mouse though, ugh.

We are in Arlington, WA. About an hour and a half NE of Seattle. I need the brakes fixed before I'm mobile again, so any repairs have to be onsite. (I'm leaking brake fluid, even when parked.)

My toddler and I are full-timers and depend on the furnace to keep us warm. We need a workable solution.

Thanks,
Bryanna and Carlin

BryannasTreasureBox · 01-19-2005, 08:06 AM

Greetings,

I own a 1984 30' Winnebago Chieftain. Last winter I was having intermittant problems with the furnace, and had it and the thermostat replaced new. This winter the same problem, the furnace blows but doesn't click to light. This is intermittant and seems to be related to the outside temperature. When the outside temp is less than 20 the furnace blows only cold air. When the inside temp is less than 45, the furnace blows cold even when the thermostat is switched to 'off'. Yesterday the outside temp was 55-60 and the furnace ran fine.

Thinking it was a propane pressure problem, I switched to a new full 40# propane tank. I have a hose extension running to a portable tank. The stove, fridge, and oven all burn fine at these temperatures and hooking up the new tank didn't change anything. We are hooked up to 110 via an adapter, plugged into a standard electric outlet in the garage.

I'm on an Energy Assistance Program for low income and they contracted to have the new furnace installed last year. It was a general handyman type. He didn't do any diagnosing, just recommended replacement of the 20 year old furnace and the EAP paid for it. (I kept it for spare parts.)

A friend thinks there might be water vapor in the propane lines and it freezes. If so, how do I fix that?

The furnace say 'Suburban' and the installation paperwork I have says DynaTrail, instructions for models nt-24sp, nt-30sp, nt-34sp. I couldn't find a model number printed on the furnace itself. did find a dead mouse though, ugh.

We are in Arlington, WA. About an hour and a half NE of Seattle. I need the brakes fixed before I'm mobile again, so any repairs have to be onsite. (I'm leaking brake fluid, even when parked.)

My toddler and I are full-timers and depend on the furnace to keep us warm. We need a workable solution.

Thanks,
Bryanna and Carlin

Gary RVRoamer · 01-19-2005, 03:00 PM

A strange problem indeed and obviously an urgent one at this time of year!

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR> When the outside temp is less than 20 the furnace blows only cold air. <HR></BLOCKQUOTE>

If a DSI furnace doesn't light, the fan usually keeps running (depends on furnace model and how it was wired). I'm assuming this is a DSI (direct spark ignition model rather than one with a pilot light, right? Your old one may have had a pilot light, but the new one is probably electronic ignition.

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR> When the inside temp is less than 45, the furnace blows cold even when the thermostat is switched to 'off'. <HR></BLOCKQUOTE>

Ah, how is that again? The furnace runs when the thermostat is OFF? Sounds like an installation screw-up to me. 'Off' isn't really off. What is the temperature setting on the t-stat when this happens? It is probably above 45 and thus calling for heat, which apparently has triggered the furnace to start. Does this also happen at 50? 60? And you said it blows cold air, so that means the furnace doesn't light in these conditions either? Please clarify the symptoms a bit more on this part of the problem and maybe we can figure it out.

Your surmise that there is a line bloackage that freezes up sounds like a good one. Both water and oil can get into the line and casue this sort of problem. Since other appliances continue to work, it sounds as though the blockage is fairly close to the furnace. The usual fix is to disconnect the line at both ends and blow it out with compressed air. However, a good pair of lungs is sometimes sufficient to huff & puff it out (don't inhale the propane though!). And if you can get the line oriented right with no low spots, it might even drain out on its own if left a couple hours.

BryannasTreasureBox · 01-19-2005, 06:40 PM

Both the old and the new are electronic ignition.

The thermostat has a lever to set the desired temperature 50-90. All the way to the left is 'off'. When the inside temp drops below say 45, the blower starts without the thermostat telling it to. I watched without the cover and the mercury bubble does not complete the circuit, but there is plenty of cold air.

When everything is warm inside and out, then the furnace works just fine. Today we had a high of 58, and the snow is gone. The furnace runs fine. I don't get it...

So how do I blow out the hose? My neighbor has the tools and an aircompressor. Where do I find the propane connection at the furnace? fThen disconnect from the auxilliary tank, aim the airhose at the propane hose and let 'er rip? Anything else?

Thanks,
Bryanna

RV Wizard · 01-20-2005, 01:44 AM

To get the thermostat to the off you may have to push a little harder to the left untill the lever actually clicks over into a notch. Have the pressure regulator checked under load by a trained lp gas technician and diagnose if there is a possiblity of contamination of the line &/or regulator. Keep us posted as to the results.

BryannasTreasureBox · 01-20-2005, 10:02 AM

yep, even when the thermostat lever is clicked over to 'off', the furnace fan runs. but only when it's cold inside, like under 45. It shouldn't but it does.

I will call my EAP program and see if they have an LP tech that can come out.

Thanks,
Bryanna, who's not very handy but willing to learn.

BirdRacer · 01-20-2005, 12:21 PM

I would suspect moisture freezing in the lines also, and I think your Thermostat is wired incorrectly.

Kirk · 01-21-2005, 12:23 AM

None of these theories would explain why the blower runs when the furnace is turned off? And it is the old mercury type theromstat? I thought that they had stopped making those?

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR> when the thermostat lever is clicked over to 'off', the furnace fan runs. but only when it's cold inside, <HR></BLOCKQUOTE>

This inspite of the fact that it worked for a year? Are you sure that your not putting us all on? I have seen this post on several different forums. Why does this seem like a hoax to me? I'd be happy to help if possible but if this is really legitimate, then you need a lot more help than what we can do via the net!

RV Wizard · 01-21-2005, 01:45 AM

I think that the thermostat is bad. To double test this theory remove the wires on the thermostat. The blower should not come on at any temperature. The other problems are going to have to be trouble shot for repair.

Gary RVRoamer · 01-22-2005, 07:12 AM

As RV Wizard suggests, disconnecting the t-stat is the first step towards isolating the unexpected fan start-up problem.

It is possible that a wire is being pinched or a circuit board is shorting when things contract as the temperature falls. That might explain those starts and other strangeresults when it gets real cold.

As for cleaning out the lines, disconnect both ends (make sure propane tank valve is OFF!) and jury-rig some method of hooking an air line to the propane tubing. You don't need (or want) real high pressure, so it doesn't need to be a tight seal. You may be able to simply hold the end of an air chuck against the tube opening, if the air chuck is shaped right. There is no way I can tell you where the lines are on your rig - you just have to find it somewhere on the back of the furnace and trace it to wherever it joins the main LP feed line in your rig. Sometimes it is simple and sometimes not.