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front furnace malfunction

January 29, 2013, 09:55:06 am

I have always gotten great help her so here goes the new one. My front furnace in my 1989 Grandvilla is giving me problems. I am only trying to cut my troubleshooting curve short. I can have a furnace person some out, but like some of the other forums states, "Why have an expert come and give me the answer right away when I have everyone here?" It worked fine for some time. Then it began to run a little bit longer and more often than the rear furnace and in this longer running times it would "sputter" through the firing cycle every once in a while. Then this "sputtering" kept getting worse and longer. Finally, last night. I turned the thermostat from being at work to 70 degrees. (Yes, I would turn it down to 50 degrees while I am away) While waiting for it to warm up the furnace in the rear cycled perfect, but this time the front furnace did not even get the "sputtering" with the cycling. The blower would only run with no heat ever coming out. I would hear no part of the firing cycle at all. I know I have propane because the rear furnace works fine. This is what I know so far. If anyone can help me narrow it down to the part(s) I need then it will save me time and that illusive commodity -  money. It is nice because I live near Montpelier, Indiana. Ickes RV surplus and supply has all kinda parts for RVs. I am typically shocked at how inexpensive their RV parts are. I have called multiple furnace people already and they don't even want to look at an RV furnace. Why, I do not know. Thanks ahead of time for all your help.

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Re: front furnace malfunction

Reply #1 – January 29, 2013, 11:02:36 am

It may be the circuit board? Take the circuit board from the rear furnace and install it in the front furnace and see if it works then.
Not an original idea from me, read it on this forum.

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Re: front furnace malfunction

Reply #2 – January 29, 2013, 01:45:33 pm

If swapping boards fails to pinpoint your problem, you might check your burner assy.  The screen on my burner was cracked on my furnace and failed to get a proper flame.  The thermocouple would shut off the gas supply when the proper flame was not sensed within the correct time frame. You have to disconnect the LP supply line to remove the assembly for inspection.  Shut off the main tank before removing the supply line.  Not a difficult repair.  (Hydro-flame)

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Re: front furnace malfunction

Reply #3 – January 29, 2013, 09:13:12 pm

It sounds like a bad burner, you can check with Gary O as he just repaired a hydra flame furnace yesterday and can give you many pointers about it

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Re: front furnace malfunction

Reply #4 – January 30, 2013, 02:20:40 pm

Find the Heater 12v Fuse, remove and push it back in several times, sometimes the contacts get cruddy, same with the Thermostatic use a piece of paper placed between the contacts, scrub the paper back and forth to clean them.  Next verify you have 12v+ to the positive wire, 10 or 11v will not do it. Next remove the sparker assembly, scrape the electrodes with a pocket knife reset the gap to about 1/4in.  Finally if those tricks don't work it's the circut board, or the Sail Switch.  When replacing the board be sure to use a Gorilla Board.  Sail Switch, call a RV Guy, furnace needs to come out, it's a project.

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Re: front furnace malfunction

Reply #5 – February 01, 2013, 05:00:52 pm

I had a HVAC guy come out. The little white circuit breaker was not fully sticking out, but it was blown. I would have not believed it if I wasn't holding the volt meter. Then when it began to work and make heat, it was still sputtering. He gently tapped on the gas line and the sputter got less. He did this three more times and smooth. He looked at me and just said, "Bad gas" change your provider. Many deliver moisture with the gas, he said. Not good. He said if it happens again, do this and you should have no problems. Being a low of 3 degrees the last two nights, I got it fixed just in time. Three days ago it was over 60 degrees. Welcome to Northern Indiana. Thanks everyone.

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Re: front furnace malfunction

Reply #6 – February 01, 2013, 06:46:19 pm

On this subject, 
Is there a way to access the furnace motor short of rtemoving the whole furnavce from the coach ?
On startup  in the  morening mine SQUALLS, I suspect that the motor is trying to seize up and if I could get to it that I could lube it in some way.
Gary B

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Re: front furnace malfunction

Reply #7 – February 01, 2013, 09:22:43 pm

Gary bad news, it's got to come out. First make a trip to hardware store or Home Depot get a electric motor oiler, it's a small plastic bottle with a piece of plactic tube that pulls out about 12" for getting into tight places. Caution when removing any under counter unit be really careful and look for sharp edges and sheet metal screws that might get hung up when pulling the unit out.  Cover the Kitchen table with several sheets of cardboard, then use it as a table.  Remove the top sheet metal cover of the furnace marking screw lengths. Now the fun starts, you need to remove the Squirrel Cage Fans in order to lube both bearings of the motor. Mark fan locations on shaft before removal with a scribe or felt tip pen. Assemble, lube should be good for 3 or 4 years.
Might be easier to call the RV Guy.

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Re: front furnace malfunction

Reply #8 – February 01, 2013, 09:33:46 pm

Gary,
  I have taken mine apart completely down to the heat exchanger through the door in the unit. Not the easiest thing to do but possible. I think Gary O has also. He was the one who told me it was possible.

Mark Z

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Re: front furnace malfunction

Reply #9 – February 01, 2013, 11:37:07 pm

It's not necessary to pull the whole unit to lube the motor, but you do have to pull the motor (access through the outside door).  Main thing to get is a set of long T-handle Allen wrenches.  You probably won't have to replace the motor.  Lubing it with a good electric motor oil (NOT 3-in-One!) usually does the trick.

Here's the writeup from Barry Brideau's site:

Atwood Furnace Motor Replacement

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The motor is clamped inside a steel collar, that is attached to a steel vertical partition. There is only a single machine screw that clamps the collar together, over the motor. The motor has a shaft coming out of each end, in which two fan cages are attached. There are two wires connected to the motor, where it enters the collar. These are the 12v power supply and a ground wire at the collar. Look for these wires and you will see the collar screw.
To begin, make a rough sketch of the wiring, and disconnect the power.
To get the motor out, you need to lift up the black plastic shroud, which has the majority of the wiring attached to it. Most of the wires can remain connected at this point. First remove the printed circuit board assembly to make some room to work. This is on the left side, attached with a wing nut and it will slide out towards you with a bit of jiggling. There are four self tapping screws holding the shroud in place; after removing them gently lift the shroud towards you and upwards. You may have to disconnect a few spade connectors to make this possible. Be careful, the rather delicate sail switch is attached to the back of the shroud. You can use a piece of string to hold the shroud out of the way.
You will need to loosen the small fan cage, on the gas valve side of the vertical partition, to pull the motor out. Use a long allen wrench to loosen the grub screw, attaching it to the shaft. If you encounter any rust on the shaft, preventing the fan cage from sliding off, use a small file to remove the rust and a bit of oil. Rotate the fan on the shaft and you should be able to work it loose.
You may find it easier to remove the burner assembly and exhaust pipe to make more working room, but it is not necessary. If you want to do this, the exhaust pipe pulls straight out towards you, after you loosen a wing nut, but you will probably have to jiggle it, if has been in there long. The burner assembly is another matter, there are three self tapping screws and you will have to disconnect the propane fitting. It can be done but takes time and more jiggling.
Put it all back together, in the reverse order, with the new motor.
And you will be all set.
© Barry Brideau 2008-2013

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Re: front furnace malfunction

Reply #10 – February 01, 2013, 11:47:14 pm

We changed our furnace motor ourselves, from outside door opening.

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Re: front furnace malfunction

Reply #11 – February 02, 2013, 11:40:42 am

Thanks all, Gary O also gave me some good tips, Think I will wait til we get back home to tear into it.  I knew there must be a way short of pulling entire furnace.
Gary B

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Re: front furnace malfunction

Reply #12 – February 02, 2013, 12:03:46 pm

Gary, I had the same problem and it was simply realigning the motor. The fan was rubbing on the sheet metal. Loosen the fan screws a bit and try moving the motor around while it is squealing. IF it stops you know that is the problem and then it is just a matter of find a happy place for the motor and tightening the screws back down.

Fortunately I have found most problems with my coach have been simple. I used to dive head long into repairs but have since learned to try the easiest things first. Hard to believe if you have know me for a long time, but true.

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