2004 Skyline Nomad Park Furnace

[Aquafuzz]

Just picked up an 04 Nomad park model that has been used only during the summer months and the furnace has not been turned on for 7 years.

There is no 12vdc system in this camper. There is a 110vac cord coming from the furnace and a couple of wires running to the thermostat. The propane valve at the furnace has been turned off this whole time as far as I know.

Is there a startup procedure to a checklist to go over before firing it off?

Is there anything to check as far as the ignition system to ensure it’s sparking?

Anything to check with the blower system?

Just trying not to blow myself up.

 

[Kirk]

Brand and model of the furnace would help to answer your questions. In an RV the furnace is 12V & propane but most manufacturers also make a 120V version that is often found in the same service manuals. Also with the make/model there is a good chance we can find an operators manual that you can download.

 

[Lou Schneider]

Yes, verify the furnace make and model before you plug it in! If you can't do that, I'd take the power to a 12 volt battery and see if the blower runs a few seconds after you turn on the thermostat or short the thermostat wires (same thing).

If the blower doesn't run, plug it into 120 volts and try it again.

Shortly after you get the fan running you should hear the click of the gas valve and the sparker trying to ignite the flame. Shut it down again, turn on the propane valve and check for leaks.

The start-up sequence is the thermostat calls for power, the fan starts and when it comes up to speed it trips an airflow switch. If the sail switch successfully closes the furnace then turns on the gas and starts sparking to ignite it. If the sail switch doesn't close or the flame fails to ignite the fan will continue running a minute or so to get rid of any accumulated gas fumes. Or it will continue running until the thermostat turns off.

 

[Aquafuzz]

Brand and model of the furnace would help to answer your questions. In an RV the furnace is 12V & propane but most manufacturers also make a 120V version that is often found in the same service manuals. Also with the make/model there is a good chance we can find an operators manual that you can download.

Thanks, I'll be back at the camper in a few weeks and I will dig up a Brand and Model and report back.

 

[Aquafuzz]

Yes, verify the furnace make and model before you plug it in! If you can't do that, I'd take the power to a 12 volt battery and see if the blower runs a few seconds after you turn on the thermostat or short the thermostat wires (same thing).

If the blower doesn't run, plug it into 120 volts and try it again.

Shortly after you get the fan running you should hear the click of the gas valve and the sparker trying to ignite the flame. Shut it down again, turn on the propane valve and check for leaks.

The start-up sequence is the thermostat calls for power, the fan starts and when it comes up to speed it trips an airflow switch. If the sail switch successfully closes the furnace then turns on the gas and starts sparking to ignite it. If the sail switch doesn't close or the flame fails to ignite the fan will continue running a minute or so to get rid of any accumulated gas fumes. Or it will continue running until the thermostat turns off.

Thanks for the basics. Ive used similar systems that ran on diesel and were 12vdc only systems. Just wasnt sure the operation was the same, sound real close. I'll be back at the camper in a few weeks and I will dig up a Brand and Model and report back.

 

[Aquafuzz]

Brand and model of the furnace would help to answer your questions. In an RV the furnace is 12V & propane but most manufacturers also make a 120V version that is often found in the same service manuals. Also with the make/model there is a good chance we can find an operators manual that you can download.

The model is an Atwood 8940-111-ACLC furnace. There are two blue wires that ran to my thermostat and a 110 plug. One blue wire was connected to a red wire labeled RH at the thermostat and the other was connected to white wire to the thermostat.

I have the furnace out and at home and want to bench test, what do I connect to the blue wires?

 

[Kirk]

I looked up your furnace and yours is a 120V-alternating current model as that is what the AC means in the model. The LC means that it comes set for burning propane but could be converter to natural gas, which the LP models can not. If you download this service manual from Bryant RV Service, you will find that on page 7 there is an explanation for the model designators. (8940-111-ACLC)

what do I connect to the blue wires?

The two blue wires normally would attach to a mechanical thermostat and to call for heat the two contacts close. In bench testing, if you have the furnace connected to 120V power, shorting the two together will act as the thermostat closing and the blower should start to run and then after a delay the gas valve will open and the ignition probe will spark. You can confirm this by looking on page 12 of the service manual once downloaded.

 

[Aquafuzz]

Thank you everyone for the help. After cleaning out some mud-dobbers and a few other insects, checking all the wiring, checking the gas valve solenoids and finally the igniters, I put some gas to the system and got heat!

 

[Gary RV_Wizard]

Thanks for the feedback - good to learn if our advice was correct.

 

[Aquafuzz]

So interesting thing. When bench testing I used the same lines and regulator but not the tanks. I used my tank from the grill.
During testing it would fire right off. Now that the furnace is in place when it fires it’s like it sputters 3 times and finally it catches and heats.

Any ideas?

 

[Kirk]

I would let it run for a while before trying again just to be sure that there isn't any air in the lines. Then try it with your other tank to see if it gets well.

 

[Aquafuzz]

I would let it run for a while before trying again just to be sure that there isn't any air in the lines. Then try it with your other tank to see if it gets well.

I thought it was Erin the line at first as well, so I let it cycle throughout the night and it continue to do that little sputter thing before it catches. After doing a little bit of digging on a couple other threads I believe it has to do with the temperature and the low pressure issue when the cylinders are cold. When I was testing it was almost 80° and the tank was in full sun. Now that I’m at the location where the heaters installed it hasn’t gotten above 50 lows in the low 40s and no direct sun.

 

[Kirk]

Now that I’m at the location where the heaters installed it hasn’t gotten above 50 lows in the low 40s and no direct sun.

Liquid propane will boil at -44°F so unless the tank is very nearly empty, that should have no effect. When a tank is near empty that will have an effect on the supply pressure and volume. It almost sounds like it was picking up a little bit of moisture somewhere...... Is it possible that the location of the furnace plays some part?

 

[Aquafuzz]

Liquid propane will boil at -44°F so unless the tank is very nearly empty, that should have no effect. When a tank is near empty that will have an effect on the supply pressure and volume. It almost sounds like it was picking up a little bit of moisture somewhere...... Is it possible that the location of the furnace plays some part?

Both tanks are at about 3/4 full.

The propane stove seems to work fine.

How would it pick up moisture?

Explain more about location. Not that I can move it but I’d like to know your thoughts.

I rechecked the igniter gap and opened it up bit, close to a 1/4” and it seemed to help a bit. Now it only stumbles twice verse 3 or 4 times.

Just seems odd that when I had the unit out and connected to grill tank it fires right off.

 

[Kirk]

Just seems odd

I agree with that. Frankly, I am grasping at straws to come up with a theory of what might cause the problem. Sometimes propane can have some oil residue in it to a point that houses with propane appliances have an oil trip just before the connection to each appliance as a part of code. I wouldn't expect that to be happening and have never heard of it, but.....

Did you clean the burner area and the burner head?

 

[Aquafuzz]

I have not cleaned the burner area other than to blow it off with compressed air and wipe it down. There is some surface corrosion, but nothing is be concerned about. Again cleaned the burner head the same way.

Might have to bring my grill bottle with me next time I go up and try that. Maybe something with the bottles. My guess is the stove is more forgiving than the furnace.

 

[Kirk]

Might have to bring my grill bottle with me next time I go up and try that. Maybe something with the bottles. My guess is the stove is more forgiving than the furnace.

I'd say that is good thinking. At least then you would know if the bottles are the problem. I'm hoping that proves to be the cause, but will keep looking for other possibilities.

 

[ChasA]

Get a manometer and check the gas pressure. I had a persistent problem with my furnace. The mobile tech I called tested the pressure and found it to be 8" of water column. Every other propane appliance worked perfectly, but the furnace didn't like it.