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HiHoAgRV · 11-19-2008, 07:04 AM

Quote:

Originally Posted by HowieE

...The main gas valve on the heater will only come on after there is PROOF OF PILOT. If there is air in the line the pilot valve is too small to bleed off the air in the time allowed for proof of pilot and the cycle will just time out.

Lazy person reply here...
Both my Airstream and SOB suffer form this problem and my method is to get the stove top lit to purge the main gas line. This usually takes a few minutes of holding the firestick ove the burner before she fires up. I can then turn on the heater and if it doesn't fire, I cycle the thermostat to "off", wait 5 seconds the go back to "on". It may take a few tries but she always fires up.
This process can be done with a single had, freeing the other to hold a beverage

HowieE · 11-19-2008, 08:14 AM

Quote:

Originally Posted by HiHoAgRV

Lazy person reply here...
Both my Airstream and SOB suffer form this problem and my method is to get the stove top lit to purge the main gas line. This usually takes a few minutes of holding the firestick ove the burner before she fires up. I can then turn on the heater and if it doesn't fire, I cycle the thermostat to "off", wait 5 seconds the go back to "on". It may take a few tries but she always fires up.
This process can be done with a single had, freeing the other to hold a beverage

Yes this will work. But the average individual does not have the patience to go through several cycles and purge the line using the pilot valve and will yield to the service tech who will do just that and charge them for a circuit board.

Maxom · 11-19-2008, 04:59 PM

OK, now I am the dummy here. I worked for two hours trying to get the Surburban in the '72 Sovereign to fire up. MAnaged to get gas to the pilot, opened the little bottlecap pilot door and stuc in a match like the manuel said. It didn't say the bottle opening would spew flame like a little rocket. Despite having no hair on that hand now, I'm otherwise unhurt. Now I see a note here about the voltage. I didn't even have the power on, so the durned thing was not going to work no matter what. Oh well at least I have the forum here to fall back on; as long as I don't burn my fingers too much to type.

The things we learn about Airstreams after we buy them would be worth knowing before.

bryanl · 11-19-2008, 05:21 PM

Quote:

didn't say the bottle opening would spew flame like a little rocket

This is one reason why the blower is supposed to come on a few seconds before primary ignition. The sail switch is the indicator that the blower is indeed working. A part of the blower runs fresh air through the combustion chamber and it needs to be clear of residual gases before attempting to start up the furnace. On shutdown, the gas valve turns off the main burner and the blower continues for a while to make sure all combustible gases have cleared.

The question is why you got singed. A pilot should not do that even if you held down the thermocouple over ride for quite a while. The gas valve for the primary burner should not open unless the sail switch indicates proper blower operation and a time delay. The thermocouple is the primary safety for gas shutdown if no heat is being produced.

The auto ignition things work a bit differently as they have a sensor to determine if the burner took off and will shut down the gas valve if they don't detect flame after ignition. This is often an ion sensing thing looking for the flame's plasma.

You need to see if you have a leaky gas valve or something. An extra enthusiastic pilot lighting exercise is a warning about a potentially explosive situation.

Maxom · 11-19-2008, 09:40 PM

Thanks Bryan. Actually I have not yet gone back to try anything else, but I think I will try one more time to make sure there is 12VDC going to the thing before I try again. The furnace looks to be in good physical shape, and while I was convinced that the push button spark igniter was not working, I saw that it was after taking cap off and looking into the pilot hole. So it gets spark and it gets gas, sort of. I am still thinking the flash I got was from trying so long to get the pilot to light. And I am hoping that by giving the rest of the system a fighting chance with electricity, it will give me the same result as did the oven and stovetop; both of which work great.

This is a '72 that I bought for $500 on a bet, since it had been sitting on a lot untouched since 1983. The owner of the trailer was not the owner of the lot and there was some bad blood going on there. And the owner lost the key, "a while ago", and had never went back into the camper. I bought it, hauled it home and managed to pick the lock. Inside I found a time capsule from 1983. This was a sort of summer place for the owner's family, and when they left they had every intention of coming back like the next weekend. They left everything. Even the change bowl by the sink, with silver dollars in it. I inherited such odd things as a complete set of the old Spiro-Graph toy, board games, a drawer full of vintage maps, fishing tackle; including some old lures still in the boxes, and all types of kitchen gear, toys, bedding and even clothing. None of that fit. Oh, and of course I will replace the funky green carpeting. Probably use new laminate flooring for that.

When I bought the trailer I intended to gut it and do a remodel. But when I got inside and started cleaning up, I found that the inside was in remarkable shape. About all I now intend to change out is any appliances that don't work and can't be easily fixed, and all the foam cushions in the upholstered areas. Who knew those just turn hard over time and break instead of giving?

bryanl · 11-19-2008, 10:48 PM

Quote:

Inside I found a time capsule from 1983

what a story, what a find!

The furnace should be OK. I never found the spark igniter on those to be worth much and found a propane lighter much more convenient. Do check the outside vents for any obstructions. When the blower motor went, I found a auto ignite newer furnace surplus for under $400 and left the pilot lighting behind.

Also, I have heard you need a window on the opposite side of the trailer cracked open to facilitate pilot lighting. Sounds weird but it seems to have made a difference for some.

Maxom · 11-20-2008, 04:02 PM

Brian,
I poked around some more on the furnace. Tried a few more times to do the pilot light, and got it to burn for a few seconds at a time. It looked like a clean pilot flame but it just wouldn't stay lit. Read back through some of the info here and in the manual. Oh yea, forgot to tell you that one of the things I inherited in the trailer was a full shop service manual, along with the owner's manuals for the trailer and all the appliances, etc. The service manual is a wealth of information. It is for the whole line of '73 Airstreams, and mine is a '72. But It can't find any differences between the two.
One of the furnace issues that seemed out of place was the idea that when you turn the thermostat up off the bottom peg, the fan should come on. After making sure I had 12 VAC going to the thing, I tried that and got a click but no fan. I was not yet convinced to try to take the furnace out of its cabinet so decided to look around some more before going that far. The easiest next thing to take off was the outside vent cover. Took that off and found a major problem, and was glad the thing didn't light. The intake side, or the bottom tube, had what looked like a green filter in it. Looking closer I decided it was not a filter but something more like moss. I started poking at that and it came apart to easy to be something that was supposed to be in there. OK, I got a longer probe, which turns out to be a great use for the aluminum rod handle that is for the awning wheels.
Started digging and got out a mass of fiber, moss, insect carcasses, wasp nests and other gunk. The whole wad of stuff was about a coffee mug full. I could then see the fan motor and what I thought was a shaft to the blower, and some more gunk. I decided to see what happened if I turned the thermostat up again. Wow! the fan came on; although it was noisy. I let it run a bit, shut it off and then went back out to examine the fan inside the vent hole. What I could see now looks like the fan itself is totally clogged up with mud dabber nest. That would account for it being out of balance and noisy.
Now I plan to figure out how to get the furnace our of the cabinet. The manual talks about cutting a hole in the shelf to get to a latch that allows you to open the furnace cover. There is already a small hole there that looks like probably someone has been in there before. But I tripped the latch and nothing happened; so far. I'll keep probing gently and get the thing out so I can get it on the work bench. I'm betting a good cleaning and it will all work fine.

bryanl · 11-20-2008, 04:44 PM

Quote:

It looked like a clean pilot flame but it just wouldn't stay lit.

on a pilot based device, that is usually a thermocouple problem

Quote:

What I could see now looks like the fan itself is totally clogged up with mud dabber nest.

wasps and spiders seem to like the perfume they put in propane. It is always a good idea to check the furnace and water heater before firing them up each season.

Quote:

Now I plan to figure out how to get the furnace our of the cabinet.

That can be an interesting challenge. It is often a puzzle and there always seems to be some hidden screw or gotcha' to figure out. good luck. You are probably right that it won't take much to get it back into prime working order - once you can get it on the bench!

Maxom · 11-21-2008, 05:20 AM

I have a question for everyone on this issue. If there is the need to open the gas line to purge the air in order to get gas to flow to the furnace, is there a reason not to just put a tee in the line above or below the furnace hand valve and then put a purge valve on that tee? It could just be another valve like the hand valve, and either run a purge line outside or just let it vent at the valve. Anyone ever try this? I figure if I have to take the furnace out to service it anyway, this would be an easy modification to make at that time.

**azflycaster** · 11-21-2008, 05:34 AM

You can purge most of the air from the lines by simply lighting the stove. I would not complicate things by adding any additional valves.

Jim in Pima · 11-21-2008, 06:57 AM

Just removed the old furnace from my 75 sovereign, not bad, take off the outside vent cover, you will see another plate with two wcrews into the furnace..remove them, now remove the inner front cover, the latch on mine had a screw way up top, that I got out with a stubby screw driver, take itoff. you shoudl have 4 wires hooked up to the unit, unhook them, mark what went to what.
Lower right corner on face of furnace Ihad a bolt, remove it.
On mine the gas line was on the right, had to slide it part way out of the steel case to get at it, make sure your gas is off, unhook the gas line, use a wrench not pliers. At this point it should slide out with a bit of swearing. Give it a good cleaning. once out you can hook it up to a battery and see that the electric part runs ok.
get the polarity right, tie the blue wires together and it should run. I would also pull the burner tube and clean it with a wire brush.

HowieE · 11-21-2008, 07:51 AM

Quote:

Originally Posted by Maxom

I have a question for everyone on this issue. If there is the need to open the gas line to purge the air in order to get gas to flow to the furnace, is there a reason not to just put a tee in the line above or below the furnace hand valve and then put a purge valve on that tee? It could just be another valve like the hand valve, and either run a purge line outside or just let it vent at the valve. Anyone ever try this? I figure if I have to take the furnace out to service it anyway, this would be an easy modification to make at that time.

An interesting question and one I most admit I have thought of after have to open the gas line several times. However I think it is not worth the risk. If anything ever happened and the insurance company found that valve that would be the end.

As I mentioned above I think the air enters the lines during tank refilling when the line pressure has been reduced. I must admit I have removed both tanks more than once to have them filled. I will try not to do this again and see if the problem ever occurs again.

Historically I have had the problem first thing in the spring because I remove the tanks during the winter and both gas lines are just sealed with electrical tape to keep the bugs out. This last occurrence I had removed both tanks at a Fly J and had the problem the next time I used the heater.

Jim in Pima · 11-22-2008, 06:57 AM

Something to note.
I have rehabbed about 20 campers over the years, and a point that has not been brought up. Before I fire up any of the appliances I take them out, clean them, lube them and bench test them. This saves me a bundle by not damaging units that have been off for years. Furnaces and Fridges are sure to have bees nests and spider webs and dirt. Its a pain but if you can remove the AC covers, take a hose and really washout the outside, cannot believe the dirt that comes out of the fins etc. Alittle lube on the motor, clean the fan blades, see that they are straight. Flush the holding tanks and water system, black water tanks can be really filled up, I fill it up and put a septic tank chemical in them.

Pacerized · 12-03-2008, 05:36 PM

Well 2 full months after I started this thread I was finally able to put the time into the furnace that I needed to today. With the hours I work, kids, and trying to work on the house before the worst of winter set in I just had to put the airstream on the back burner. I started by testing the gas via igniting the chamber with a long lighter. I doubt if I would have been able to get the gas fitting off without breaking it, but testing this way worked and I was getting gas. I checked for power at the limit switch and had it so I bypassed the switch to see if the furnace would ignite. It started right up using the old starter. I put the switch back on and it started again. I put everything back together and tested it several times in which it started each time. I'm not sure if I had a bad connection at the limit switch or not before but it seems that was my problem. I'll check on the price of a new switch and if it's inexpensive I'll order one tomorrow.

Thanks to everyone for the advise.

Charlie

Aage · 09-11-2009, 08:21 AM

I'm also having the "pilot won't stay lit" problem, and after reading this thread and pondering the Service Manual, I'm just about ready to take mine out and have a look inside. By the way, when it runs, it runs very well; quiet and plenty of heat.

My problem appears to happen when the furnace is off, since it usually occurs after the furnace has cycled off and on several times in the night. I know when it's happened because the furnace's blower doesn't shut off.

However, I did take the exterior vent cap off to check out if something was blocking air (or exhaust) flow and found that I could not see what the "vacuum intake cup" as the manual calls it. Here's a picture of a side view from the manual:

Now, maybe my eyesight isn't perfect, but I would figure that cup should be obvious from the outside. When I looked into the opening, I thought that I could see the "squirrel cage" of the blower. I intend to check that again when I'm back next week.

ANother mystery: the manual claims that drafts shouldn't be able to blow out the pilot since the chamber's air intake and exhaust are at the same atmospheric pressure, but I DO sometimes feel a draft in the bottle-cap opening when it's windy outside. A bad gasket somewhere?

It's starting to get cold at night here, so any and all suggestions and advice would be appreciated.

Jim in Pima · 09-12-2009, 08:13 AM

HI
done a few of these furnaces, sounds like a original Suburban. Two items to check, #1 crud on the pilot light so flame is too low. #2 Bad thermocouple, or just aloose connection. If you can reach the pilot with a "tooth brush" give it a good scrub, then blow some air at it. I ended up replacing mine as the heat exchanger rusted through..that is fatal.

Aage · 09-12-2009, 10:27 AM

Thanks for the ideas, Jim.

Can you tell me where I could get a new thermocouple? Marksrv.com has some parts ofr my furnace, but I can't find anyplace wtih a thermocouple for it for sale (Suburban NT32).

flashbackk · 09-12-2009, 12:36 PM

This is going to be my next project when i get time. I want to pull my sub and give it a good cleaning. Andy has a thread somewhere about carbon buildup inside the chamber and gently tapping it loose with a hammer.. I suspect that that is my greatest problem. The smaller volume of the chamber with all the carbon buildup.