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Old 10-17-2014, 07:59 PM   #1
trueweb
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Another furnace question

Something is up with the furnace on my 2008 Raptor 299MP. It runs for 30 seconds or so then cuts off. It will do this continuously. Pretty sure the gas is never making it. I don't hear the ignitor and I don't smell gas.

My conclusion is the sail switch or the circuit board is bad since it's never getting to the ignition step.

The question is: How the heck do I get the thing out??? It's under the fridge. The circuit board appears to be completely encompassed with no access panel and I have no idea where the sail switch would be located. Are they heavy? Is it just the two screws I can see at the front of the area under the fridge?

Any tips or links to videos or photos of people doing this job would be appreciated. Thanks!
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Old 10-18-2014, 06:57 AM   #2
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Found a youtube video that describes what I have. It is just the two screws in the front holding it in, crazy!



It is now out and out of the steel box as well and on my workbench so I have access to all the internals now. Still have no idea what I'm looking at though.

Sail switch appears to be working, will test it with a multimeter momentarily. I think I'm going to try to acquire a 12V power supply so I can try running it out of the RV for testing. Anyone know what size would be required to do this? Perhaps something from Radio Shack...

Thanks!
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Old 10-18-2014, 07:45 AM   #3
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trueweb, Howdy;

I went through the same thing last year. Only
difference is I called a service tech.
They came to where I'm set-up (I full-time), and
when the furnace was out and sitting on the picnic
table we just hooked it up to a battery with some
jumper cables (actually some standard gauge automotive
wire), to use so he could troubleshoot it. Turned out
to be the the circuit board.
With the furnace out and on the bench you should be able
to see the green light that will flash and indicate a trouble code.
Dig out the owner's pamphlet to see what they (codes), are.

hankaye
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Old 10-18-2014, 07:51 AM   #4
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Quote:
Originally Posted by trueweb View Post
Found a youtube video that describes what I have. It is just the two screws in the front holding it in, crazy!



It is now out and out of the steel box as well and on my workbench so I have access to all the internals now. Still have no idea what I'm looking at though.

Sail switch appears to be working, will test it with a multimeter momentarily. I think I'm going to try to acquire a 12V power supply so I can try running it out of the RV for testing. Anyone know what size would be required to do this? Perhaps something from Radio Shack...

Thanks!
Rather than buy a 12VDC power supply, just take the battery out of your RV, build a power cable (so to speak) from a set of jumper cables and some extra ROMEX you have laying around, hook up the furnace and see what it's doing. Don't connect propane to it, just use the battery to make sure the sail switch and the ignition circuit are operational. After that, it's pretty much only the "flame detector circuit" remaining that could be faulty. Incidentally, all of those are controlled by the control board. I've seen them fail right from the factory and some last for decades, like TV's or Washing Machines, you really can't tell in the store which one is the most durable, so you more or less have to just test it, replace anything that doesn't work to get it operational again.
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Old 10-18-2014, 07:53 AM   #5
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Check the size 12volt fuse at the panel for the furnance . Then go to auto parts store and buy an inline fuse holder and fuse and use your 12 battery. On my tt there was a small piece of debris blocking the gas orifice.
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Old 10-18-2014, 09:28 AM   #6
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In the process of troubleshooting, now nothing works. There is 12V getting to the furnace, but now the ac doesn't work when I set it to cool and the fan doesn't start on the furnace, ugh...
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Old 10-18-2014, 10:03 AM   #7
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It sounds like you disconnected one of the thermostat wires either at the thermostat, at the A/C or in the furnace. As long as the fuses are intact and the 120VAC circuit breaker for the A/C is functional, there's only wires between the units that could be the problem. It's very unlikely that the thermostat, A/C AND furnace would all malfunction at the same time. You've got a wiring problem, possibly from "tinkering". Make sure it's all connected properly and nothing got pulled loose and retry.
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Old 10-18-2014, 12:16 PM   #8
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Close JRTJH, blew the fuse in the thermostat somehow. Cease panic may now commence.

Back to troubleshooting the furnace, although it's looking like I'll need to call in the pros on this one.
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Old 10-18-2014, 01:12 PM   #9
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Good to know it's working "like it was broken before the broken part broke more".... Hmmmmm <scratching my head over that comment> LOL

Have you checked the ignitor points to make sure they are clean and not carboned up? Years ago I had a low battery, tried to operate the furnace and it failed. Recharged the battery and it still wouldn't ignite. Come to find out, when the battery was low, the propane "sludge" ( guess) fouled the igniter and it wouldn't spark even with proper voltage. Cleaned the tip of the igniter and all was good.

Did you ever find the trouble code light? what blink signals did you get?
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Old 10-18-2014, 03:16 PM   #10
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There is no light or there is a bad control board. It's a Suburban NT30SP. I cannot see anything that looks like an LED on the control board. I downloaded the repair manual and have some steps to try now, I searched the PDF for LED or Light and came up with nothing.

I'm starting with checking voltage across the control board, sail switch and limit switch. The limit switch is confusing me. It seems to also be some sort of "button".

I will also check the ignitor, it's in an easy place to get to.

Thanks!!!

Quote:
Originally Posted by JRTJH View Post
Good to know it's working "like it was broken before the broken part broke more".... Hmmmmm <scratching my head over that comment> LOL

Have you checked the ignitor points to make sure they are clean and not carboned up? Years ago I had a low battery, tried to operate the furnace and it failed. Recharged the battery and it still wouldn't ignite. Come to find out, when the battery was low, the propane "sludge" ( guess) fouled the igniter and it wouldn't spark even with proper voltage. Cleaned the tip of the igniter and all was good.

Did you ever find the trouble code light? what blink signals did you get?
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Old 10-18-2014, 03:34 PM   #11
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Page 28 in this link should give you all you need.
http://trekin.digital-digs.net/Share...ice_Manual.pdf

If you do determine it's the control board, you might want to look at Dinosaur Electronics after market boards. The have a much better reputation than factory replacement boards and in most cases are cheaper to boot.

http://www.dinosaurelectronics.com/Ignitor_boards.htm
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Old 10-18-2014, 04:15 PM   #12
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Thanks!

Yes, that is the page I printed. I am on step:

"After 15 seconds the module creates spark and opens valve"

This is not happening, so I have to test the board for power and the switches next.
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Old 10-19-2014, 03:33 PM   #13
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It sounds like a manual reset limit switch. When those trip, the blower will run and the burner will not function.
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Old 10-19-2014, 03:39 PM   #14
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It sounds like a manual reset limit switch. When those trip, the blower will run and the burner will not function.
scott, I believe you nailed it. During testing I discovered a few things. For example, the sail switch is oddly close to grounds and when you try to test voltage on it you will inevitably short something and blow the fuse in the thermostat. OK, glad that's behind me. Decided to just test for continuity by activating it manually, yup all is good.

The limit switch was sensitive. I couldn't quite get it to behave consistently. However, when I was testing for 12V across the limit switch during startup suddenly the ignitor started firing. Whoa!? So I tried again without the leads touching both sides of the limit switch, nothing... tried again with the leads touching... ignition! Well, it attempted, the gas was not connected.

Seems like my multimeter was enough to trigger the board into starting the ignition process. A new switch is on the way. We will see if that fixes it.
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Old 10-24-2014, 04:08 AM   #15
trueweb
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HEAT!!!!!

It's working. It was the limit switch. Replaced it with a $10 part from Amazon. Tested without gas attached and the igniter attempted to light 3 times before it shut down. I put it all back in the steel case (pain in the butt), cleaned up the area underneath the fridge (I think this is where they put all the extra screws leftover from the build). Slid the furnace back in place and used some foam strips to seal the floor vent, hope it's heat resistant. Connected the gas, turned on the propane, fired up the range (saw this tip on some other posts), started the heat. It ran through one ignition cycle and lit up at the beginning of the second ignition cycle. Heated the cabin up in no time.

Thanks everyone for all your help!!!
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Old 10-24-2014, 05:08 AM   #16
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Amazon limit switch - $10
Avoiding an RV Tech service call - saved $100
Satisfaction of solving and fixing it yourself - priceless!

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Old 10-24-2014, 06:57 AM   #17
trueweb
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Quote:
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Amazon limit switch - $10
Avoiding an RV Tech service call - saved $100
Satisfaction of solving and fixing it yourself - priceless!

Exactly! Knowing more about your rig is also helps. Every time I fix something on my own I feel more confident about fixing it in the future. I'm also not so worried about it breaking while I'm on the road. There are still so many things I'm not familiar with that scare me, but the list of things I have a basic grasp of is definitely growing. I also get to put things back together the way I would do it, not the way someone that appeared not to give a crap did it at the factory.
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Old 10-25-2014, 09:27 PM   #18
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Congrats. It started out as "Fix it until it's really broke", but got rapidly better from there!
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Old 10-26-2014, 05:25 AM   #19
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Glad its working!! Guess being an HVAC service tech for 25 years has its perks!!
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Old 11-01-2014, 12:25 PM   #20
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My 06 raptor doing same thing curious if its same thing. Furnace us under my entertainment system inside camper.

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pickwick lake is home though.
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