Furnace-Air in gas line purge.

[Randallt-KEY]

Hi folks, still here after 15 months and still loving my camper. I fired up my furnace a few weeks ago when it got a little chilly. I only ran it a couple of times over two days. Maybe ten minutes max each time. And then it stopped igniting, even though the fan started. It felt like one of my two propane tanks was low, so I switched it out to a full one so that both tanks are now full. But that didn’t help. The Dometic Trouble Shoot suggests I have air in the gas lines and I should use a downstream appliance like my stove top to remove the air. But the furnace is at the end of the stream and that didn’t seem to help. Water heater and stove top are fine. I am also curious about my regulator, it always has a red flag, tanks full or not. Always has.

Thanks for your thoughts, happy travels, Randall

 

[LHaven]

The regulator gauge is probably toast. Your furnace's sail switch may be the culprit. If it gets sticky, or eats pet hair, it will fail to signal to the furnace that the fan is up to speed, and the ignition sequence will abort. The diagnostic is to listen for the snap-snap-snap of the igniter after the fan is up to speed. If you don't hear it, the sail switch is the best culprit. If you do hear it, your sail switch is OK and you start looking for fuel feed issues.

Given that you can get easy access to your furnace (if you have no outdoor hatch for it access can be a pain), removing and cleaning or replacing the sail switch is relatively easy.

 

[Randallt-KEY]

Thanks for that, I’ll give it a try with listening for the clicking. Unfortunately, there is no outside access. It has easy inside access under the fridge but pulling it out of the space might be a bit much, I’ll see.

 

[LHaven]

You have the same issue I had. The good news is, having seen my mobile Tech remove it once, I realize that it's nowhere near as difficult a job as I was fearing. I thought it was going to be numerous hose clamps in a really confined space. But the ducting tubes just slide easily off the unit and recess into the floor, allowing an easy slide-out of the furnace by just removing the four anchoring screws. And there's a lot more elbow room to work than I imagined.

 

[Randallt-KEY]

Great news, the duct work was my biggest worry. Will I need to remove the exhaust port outside?

 

[LHaven]

It's a slip fit of an exhaust tube inside what feels like a large O ring. You have to aim properly to reinsert it, but there's enough elbow room for you to actually feel around the back of the unit while you do it. It might be sticky from the factory the first time you pull it out, so you might need to disassemble the exhaust port once, but we haven't had to do it since then.

 

[Randallt-KEY]

Thanks! It’ll be a few days but I’ll let you know.

 

[Randallt-KEY]

Hi there, a repairmen came out and said the sail switch problem was common with that model. He filed the closure edge to allow the sail to move freely. It worked for about three weeks but Sunday morning the furnace would not come on after I let my propane tanks run to empty. Is there a workaround for this problem? Thank you!

 

[LHaven]

Hi there, a repairmen came out and said the sail switch problem was common with that model. He filed the closure edge to allow the sail to move freely. It worked for about three weeks but Sunday morning the furnace would not come on after I let my propane tanks run to empty. Is there a workaround for this problem? Thank you!

Fill the tanks! No, all kidding aside...

Did you purge the air out of the line by running your cooktop until it ignited? Then depending on the order of your appliances from front to back, the furnace may come on immediately or may need a couple more false starts before the gas gets there.

 

[flybouy]

If you opened the LP tanks too rapidly the "safety valve" throttles the flow down because it "sees" that as a leak. Those valves must be opened very slowly. I would first try closing the tank valves, loosen the pigtail connector at the tank and let the pressure bleed off. Then tighten the pig tail on the tanks and slowly open the tank valves. Repeate the gas line bleeding buy turning on all the stove burners and light them. After all burners are on with a good, steady blue flame then try the furnace again.

 

[Randallt-KEY]

Hi LHaven and flybouy, I have heat! Thanks for the advice!

 

[Randallt-KEY]

OK, maybe not. The furnace fired up after I dis and re connected the tank and slowly opened the valve. Turned on my stove top and after 4 tries the furnace lit. After it ran for about 10 minutes and the camper got warm, it shut off as expected. About twenty five minutes later after it started getting cool outside and the fan kicked in, but the furnace didn’t. I’ve tried to light it many times with the stovetop on and have done the system bleed idea twice more. Thoughts?

 

[LHaven]

You need to listen to the diagnostic sounds. Your fan will start up and run for about 10 seconds. Then you should hear snap-snap-snap as the ignitor tries to light the propane. Then you should hear a whoosh as the propane lights.

If you don't hear the snaps, it indicates the sail switch is not detecting the fan being up to speed. If you hear the snaps but not the whoosh, it means the sail switch is OK but propane isn't being delivered to your heater for some reason.

 

[Randallt-KEY]

No clicking, no whoosh. I tried disconnecting the propane tank and reconnecting and then tried opening the tank valve super slow. I lit my cook stove and sure enough, on the fourth try, I heard clicking and the whoosh and then the furnace started. I was so happy that I wrote that notice that I had heat. It ran until it switched off once the camper got warm. After about twenty minutes, the fan kicked in, but this time I was back to no clicking and no ignition. I repeated the process a few times but it is still failing.

 

[LHaven]

For no ignitor snapping, the most probable (though not only) culprit is the sail switch. I know you just had yours serviced, but sometimes the switch itself is just hinky. I ran through three of them in quick succession right off the dealer lot under warranty. The first one got hopelessly fouled by the sawdust and styro debris that Keystone routinely leaves in areas that "nobody is going to see anyway." The second one was apparently fragile right out of the box.

 

[Randallt-KEY]

Ok, thanks. I watched their show repair guy pul the furnace out and he showed my where the switch was (bottom near the rear?), but I didn’t see how the gas line fits or the electrical connection is made. But I’m willing to give it a try.