The circuit board is probably the most easily replaced item on my furnace. I should remove it and clean the connections just to see if that helps.

 

Can you tell me exactly what your furnace does or does not do?

Steve

 

On my furnace, there was debris is the combustion chamber. Spider web maybe? Cleaned up and problem solved. I might need to cover the exhaust when not in use.

 

On Suburban furnaces that is one of the first things to check. It is perhaps the most common problem and, in my opinion all Suburbans require one of the screens sold online and at RV suppliers. It is a pain in the butt to use a crowsfoot to detach the burner tube from the gas valve and when you lift the plate on top of the combustion chamber, you will tear the little gasket underneath and need a replacement (Do not do this step before checking the gas valve solenoids for continuity).

On the other hand, given the difference in design that is much less common problem in Atwoods. Each model is given to its own set of issues.

You can often hear this problem when the furnace first fires as the flame sounds like it is stuttering, for lack of a better term because the debris inside deflects the spray pattern over the ignitor. One very simple thing to try is to take your trusty shop vac and put the hose right up against the exhaust port. You would be surprised how often that is all it takes to get things working again. This part is really important. Do not have the furnace running and trying to fire while the vacuum is on!

As with any appliance, the first steps are to verify propane and voltage and then, before buying parts, make sure do the obvious in terms of checking connections, insuring there is nothing foreign in the system, etc. It seldom takes more than a few minutes to pull a furnace, if you do not have an outside access door.

Steve

 

Steve I have a suburban that is not lighting (goes click click click no flame stove works awesome) I have been reading these threads. I plan to start a thread when I go to look at it. Can you point to a general troubleshooting diagram or description. It would be a good thing for all of us to print out and keep on hand. I am thinking something similar to what came with my house furnace. All my camper came with was if if it does not light call dealer I am assuming i need to take it apart and clean. Mine is under the stove and you need to unhook the lp and remove the furnace to see anything but 1 sensor.

 

I will try to find something online. I have the tech manuals, but they are too darn long.

For a starter in your case, do not take anything apart or even pull the furnace. Use your shop vac like I just described above. May not do anything, but if you are lucky will fix the problem.

Once you can hear it clicking, you know you are all the way through the board and the board should be doing two things, powering the igniter and sending power to the valve. When you take the furnace out, plug the gas line so you can still use your propane system for everything.

Once you get the furnace out take a battery booster and hook the red and yellow leads to it (red +, yellow -). Then twist the blue leads together and the furnace will start and cycle.

If you have a smart board with the light codes, it will give you a good idea where to start.

Steve

 

Here's why I keep asking about both tanks:

I went back a re-read the original complaint. It gives an indication that the furnace worked fine on one tank (let's call it the left tank), but failed on the other tank (right tank).

Break the system down to components: Left tank, right tank, left pigtail, right pigtail, regulator, gas line, gas valve, furnace.

What can be eliminated as bad from the above list? The furnace worked on the left tank. That eliminates left tank, left pigtail, gas line, gas valve and furnace.

If both tanks were full and the tanks swapped, you could eliminate the right tank as being bad if it works in the left position. That leaves regulator and right pigtail.

We all know the new tanks have a safety valve to prevent explosive decompression in case of an accident, but what is not common knowledge is that there is also a valve in the pigtail. If the pigtail valve is defective, it can allow enough gas to run the stove (low demand) or do an inital light-off of the furnace because of the pressure built up behind the gas valve at the furnace, but not run the furnace because there isn't enough gas getting through the pigtail valve (high demand).

If it were the regulator, it is in the switching mechanism and not the regulator mechanism because it works on the left tank originally.

The only way it could be any other component in the system is if there were a catastrophic failure at the time when the switchover occurred - not likely.

So, my philosophy is cheap, easy stuff first. The pigtail is cheaper than a regulator and easier to replace.

 

AWESOME THANK YOU I have a good feeling the vacuum will do it as it was not working once on a trip then fixed itself after going down the road. Assuming debris bounced around.

This is priceless. I unhooked the gas before and went to pull the furnace out to try and figure it out. I discovered to even see anything you need to unhook the wires and remove the furnace. Having no clue what the wires were and how to make it run on the workbench I stopped. sending reps

 

Here is a suburban rv furnace service manual.

 

Here was the initial complaint:

It was cold last week when I was up in the mountains. The coldest day was 8° F and the furnace worked fine. But a few nights later in slightly warmer temperatures it failed to start. The blower would come on, I could hear the gas light for a few seconds and then the gas would stop.


I don't see anything about running on one tank and not the other, but if you wanted to test your hypothesis, why not simply switch tanks side to side?

Steve

 

Now you gotta have a meter and know how to use it, if you push ahead. It is always best to take notes and a picture anything you take things apart. Sometimes factories break away from convention so even if you have the manuals, things are not always installed correctly out of the gate.

Here is a link to a great many service manuals Service Documents and Manuals.

Now here is something I want to emphasize. Having a manual is not enough. You still have to understand what it says and to do things in the order the manual says and in some cases understand wiring diagrams. And above all else, please remember, diagnosis is crucial.

I can obtain the service manuals for my truck's engine, but I do not have much motor experience so I only go so far. Same with everything. Propane makes one heck of an explosion!!

Steve

 

You missed the rest of the initial post then, where he said:

"I don't recall if this happened on the first or second 30 lb propane tank but it seemed to work good for the first few days which would have been the first tank."

And I made the following recommendation:
"If both tanks were full and the tanks swapped, you could eliminate the right tank as being bad if it works in the left position."

 

No sense in arguing. We see this situation differently and the nature of the problem differently. Always room to disagree.

Steve

 

I was a bit groggy when I woke up and it was 50 degrees inside the trailer, so my recollection of the exact circumstances isn't completely clear. As I recall, I manually switched to the second tank at one point. That makes me think that the auto switch thingy didn't work like it was supposed to. Maybe that was the first failure because I came back inside after manually switching the regulator, turned on the stovetop to bleed air out of the system and verify that propane was flowing (low flame was observed at that time) and the furnace did catch.

The second time it failed I think I was already on the second tank (that was still quite full). I had to crank on the generator and run the space heaters in that case. Later that day the furnace was working fine.

I'll have to start keeping a diary of these types of problems so the details aren't quite so fuzzy.

 

Intermittent is just very difficult or even impossible to trace. Until you can reproduce the problem reliably, you may never know the answer and probably should not even waste your time. More than one time I got burned making multiple trips to fix a problem I never saw. The easy stuff is always easy (and not very interesting to work on). The hard stuff in another story. But that is what makes it fun!

Steve