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Old 10-04-2012, 08:55 AM   #1
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1981 31' Excella II
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Furnace Won't Start

My furnance won't start. It was working pretty good last winter although it would sometimes not want to start when cold. We are going camping this weekend and it is supposed to get a little chilly so I thought I would see if it still works. I put a new control board in it last year.

The fan comes on when the thermostat is pushed up. You can hear the valve go clunk and the ignitor sparks and I can see the spark through the view glass. The stove works so there is no air in the line. I am guessing there is an orfice that is clogged. I only see a couple of sheet metal screws at the front of the opening. How many hidden screws are there? Looks like I am going to have to remove the unit to clean it according to this manual. Mine is an NT30.

http://www.vintagetrailersupply.com/...and%2034sp.pdf

Perry
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Old 10-04-2012, 06:40 PM   #2
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Ok I have taken the thing out and cleaned the orfice and checked the solenoid for opening and closing. A 9V radio battery works great for checking the solenoid. All you have to do is put the battery across the terminals on the solenoid and it will click and you should be able to blow through it at that point. I put it back in and it does exactly what it should be doing. I know the solenoid is opening because when I have a burner lit on the stove the pressure drops when I hear is click and then it starts sparking. What bothers me is the stove burner almost goes out when the solenoid in the furnace opens. I think I may have a low pressure problem. It maybe the pressure it too low for the furnace to light. I have noticed the stove burners being kinda low. I may take my gas grill regulator and hook into the system and see if that cures the problem. I suppose the burner log could have crap in it and that is preventing it from lighting. There is a selector valve that I guess is suppose to select which tank is being used. It does not seem to matter which position it is on, nothing changes messing with that. It has an arrow that you can point to the right or left. It works in either position with just one tank on. I don't know if that silly thing is messed up or not. I could just put a T in there and get rid of it. I messed with the regulator and nothing changes when I screw the adjuster in which should raise the pressure.

Perry
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Old 10-04-2012, 07:04 PM   #3
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If I understand what you are talking about, the selector is an automatic change over feature that dual tank regulators ofter have. Is their a clear plastic tube associated with it that shows either a green or red cylinder?

This is how they function. With both tanks full and their top valves open, the gas will flow from the tank that the arrow is pointing toward. If that tank runs empty the flow will automatically switch to the full tank. The indicator will show a red section. Once the arrow is turned toward the full tank, the indicator will show all green again. The idea is to take the now empty tank and fill it and reinstall it, and wait for the other to go empty, and reset the process. If you have low pressure with both tanks full, I would say it is time to replace the regulator.

If this doesn't not resemble what you have then forget you read it.

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Old 10-04-2012, 07:11 PM   #4
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Maybe there is not enough pressure to make the selector work or the selector is messed up restricting flow.

Perry
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Old 10-04-2012, 08:33 PM   #5
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Maybe there is not enough pressure to make the selector work or the selector is messed up restricting flow.

Perry
Either one could be true. I have had auto switching regulators on three trailers counting the Airstream. I replaced the regulators once each on the other two. I had one trailer 7 years and and the other 8 years. I don't remember all the details about how long the regulators lasted before they messed up. One was not providing enough pressure and one refused to let gas flow from one of the tanks. I don't know any way to test them other than swapping with a known good one. Perhaps someone who knows more about them than I do will chime in.

Ken
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Old 10-05-2012, 06:25 AM   #6
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I am going to see is the water heater has enough pressure to start and run. I think the furnance is a gas hog of all the appliances.

Perry
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Old 10-05-2012, 07:04 AM   #7
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Propane System Checks.

Perry,
Sounds like you need a complete checkout of your propane system. Start at the regulator and work your way back to the appliances. It could be the regulator, plugged/clogged lines, leaks etc.
Attached Good Sam magazine has a great article from the RV Doctor about propane system troubleshooting and maintenance. It starts on the PDF page 23. Good luck.

RV Doctor Propane.pdf
RV doctor Propane2.pdf
RV Doctor3.pdf
RV Doctor4.pdf
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Old 10-05-2012, 07:14 AM   #8
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Thanks for the links TOP. I will do a Propane Delivery System R&R after our trip this weekend. I think we will be fine in Alabama right now with resistance heating. I also need to work on upgrading the trailer to 50A 220V or at least 30A of that 50A. Then we can run all the space heaters we want. I expect two space heaters on high will run you out of there with the outside temps above 30F. We don't plan on winter camping much. Usually we go to FL and camp in the winter.

I will do a full R&R on the furnance as well. One more thing to rebuild. Is there ever an end?

Perry
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Old 10-05-2012, 07:30 AM   #9
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Just had the same problem on my 92 LY motorhome a couple days ago. I couldn't fire up the furnaces or the water heater. Every time I tried the stove went out. If I ran the stove I could see the flames get lower as I added burners. Turned out to be a bad regulator. Replaced it and all is well. It's possible that you have a clogged line, but my bet is the regulator. At less then $30 to change out it's a cheap fix. The symptom of being bad when it gets cold makes sense too. The oil used to give propane its smell accumulates over time and get thicker when cold. Any accumulated oil in the regulator can really gunk things up over time.
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Old 10-05-2012, 01:45 PM   #10
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The bottom line is accurate

Quote:
Originally Posted by 92landyacht View Post
... The oil used to give propane its smell accumulates over time and get thicker when cold. Any accumulated oil in the regulator can really gunk things up over time.
Mercaptan, the smell added to propane is an organic compound as opposed to an oil. It, in itself, will not gum up anything as it is too volatile to stay condensed.

Oil is used to pressure-verify gas cylinders & as a part of some gas pumping systems. 92landyacht is right about oil fouling the reg. The source of the oil, though, could be lotsa things.

Perry:
* One 1500 watt heater is all we need unless the temperature drops below 40 degF.

* The pilot light jet on my Overlander's original furnace gets clogged every 3.2 years. It is taken apart & blown out when that happens.

* A 30-amp service will comfortably run two 1500 watt space heaters as long the fridge is on gas, and the heaters are each plugged in to the separate circuits your Airstream came with.

Stay warm,

Tom
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Old 10-05-2012, 02:11 PM   #11
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As pointed out in TOP's links, a manometer is needed to be sure you have good gas flow; they aren't that expensive, or you could make one, I suppose.

I didn't notice anyone listing pests (mud-daubers, wasps what have you) that can and will gather in furnaces. But you would have seen that when you disassembled the furnace, I suppose? It's hard to miss ...
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Old 10-05-2012, 02:36 PM   #12
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As pointed out in TOP's links, a manometer is needed to be sure you have good gas flow..
Perry,

I know you've seen seen all those Heise gauges rotting on the T-Stand's first floor. But if you need help with assembling a manometer, I am here to help..

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Old 10-05-2012, 02:49 PM   #13
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I think the key here is the drop in stove flame as the furnace tries to fire. Since the two appliances behavior are related I would go upstream first.

That leads to things like main gas supply pipe, Regulator, POL valve. When I had my problem I first disconnected the regulator outlet. I then disconnected a gas line going to the fridge and checked for any obstruction by blowing air back towards the regulator. I used compressed air to ensure that anything in the lines was blown out. Once I knew that I had no line blockages I disconnected the inlet to the regulator. I then checked for good high-pressure gas flow coming from the POL valve. Keep in mind that the POL valve will shut down flow if the gas flow is too high so open it slowly just to check you have good flow. If I had good flow there, then the regulator had to be the source of the problem. Since the inlet and outlet are disconnected it just a mater of replacing it and connecting all the lines back up.

I am assuming that you've checked that the LP tank is not empty.

On a side note: when I reconnected everything I purged the air from the line by allowing the gas to flow for a few seconds with the POL valve slightly open. It was also a great way to verify my newly installed LP/CO detector was working.
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Old 10-05-2012, 08:05 PM   #14
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I expect there are problems with the furnace and the gas reg. There was a ton of junk in the burner, mud dobbers, rats, rust etc. It may be burner is full of debris.
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