Furnace Will not light

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caspian2

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Was wondering if anyone experienced similar situation and has any input before if get too far into trouble shooting.
Have a 2020 Jayco 5th wheel with DOMETIC DF series Furnace. When the temperature gets to the tight level on the thermostat, the furnace blower turns on fine, but the furnace does not light/kick in, so no heat. Blower runs for a while and then stops.
I have checked thermostat and LP line/supply and all Ok (all other LP appliances working fine).
Thanks
 
Before you spend any money, open up the outside access to the furnace and unplug and plug in all the blade connectors and the edge connector for the circuit board. Those blade connections get corrosion on them and won't conduct power.
If some of the blade connectors feel loose, squeeze the female half gently with a pair of pliers to tighten them up a little.
 
Our 2018 MH was giving us equivalent issues. Kevin first checked connections - all good. He then replaced the sail switch - easy to do and cheap. Didn’t help. Next step was to replace the igniter after checking voltages and such. A knee replacement came before that happened, so we had a shop replace it. Perfect now. Propane furnaces are simple creatures compared to some of the alternatives. Parts and instruction videos are easy to come by.
 
UTTransplant said:
Our 2018 MH was giving us equivalent issues. Kevin first checked connections - all good. He then replaced the sail switch - easy to do and cheap. Didn’t help. Next step was to replace the igniter after checking voltages and such. A knee replacement came before that happened, so we had a shop replace it. Perfect now. Propane furnaces are simple creatures compared to some of the alternatives. Parts and instruction videos are easy to come by.
Click to expand...
Thanks for all the input. Will star trouble shooting with the connectors and sail switch. As others had said above, looks like sail switch is a potential. Igniter will be the next one.

Thanks and will let you guys know.
 
I've written an article on Atwood/Deomtic Furnace Troubleshooting (Suburban is nearly identical). If you under stand the process it goes thru to light and make heat, it's usually clear where the problem lies. It's in the site Resource Library at RVForum - Furnace Troubleshooting

You will get all kinds of well-meaning suggestions but don't start throwing parts at it. Do the diagnosis first.

As Pedro says, if you listen closely you will hear if the igniter is clicking. If it does, the furnace has power and the sail switch activated. If not, start diagnosis at the sail switch to see if it engaged properly or not. Low battery voltage is the #1 cause for the sail failing to engage. If the igniter clicks (sparks) but the burner doesn't light, then the problem is almost surely in the combustion air supply & exhaust tubes, e.g. rust flakes or insect nests. Propane is very fussy about the air/fuel mix needed to ignite.
 
caspian2 said:
When the temperature gets to the tight level on the thermostat, the furnace blower turns on fine, but the furnace does not light/kick in, so no heat. Blower runs for a while and then stops.
Click to expand...
That indicates that for some reason, no heat was detected.
Arch Hoagland said:
Have you checked the sail switch?
Click to expand...
This is a definite possibility. The sail switch is a safety device that must detect enough air movement for safe combustion or it doesn't close and prevents the gas valve from opening and the ignitor doesn't fire.
Pedro Dog said:
do you hear the igniter clicking? If you do, then it's not the sail switch.
Click to expand...
A very good trouble shooting technique. If you do hear it attempt to light, next check the exhaust to see if it is at all warm. Either a failure of the propane to ignite or if it does ignite but the probe fails to detect that heat can cause the symptom that you have. Either of those can be caused by a bad ignition probe as it supplies the spark and also detects the heat from the burning propane.
Gary RV_Wizard said:
don't start throwing parts at it. Do the diagnosis first.
Click to expand...
You can spend a lot on parts without any change if you do that.
 
I guess the main problem was access and getting to the furnace, as there is no access door on the outside. Based on initial trouble shooting ,with all the good input provided above (LP and voltage OK, did not hear any clicking for the ignition or smell any gas), I will go ahead and replace the sail switch. Part will be here late today. I had to disconnect bunch of items so I can move the furnace and get access to the back to remove the sail switch.
Will keep you posted.
 
Hope that solves your problem, but it's just a shot in the dark. A sail switch is easy to test, and the switch itself rarely fails. It's also easy to override (push the lever) or bypass (just jumper around the switch). When the sail switch doesn't close, it's usually an air flow problem and the switch itself is "working as designed". Or maybe a wire connection problem, where the switch closed but the controller doesn't see it. Sometimes the act of removing & replacing fixes the problem, so maybe you will get lucky.
 
Sail switch replacement worked. As I said, changing the switch was easy, just gettin to the unit and removing/replacing it was most of the work.
Thanks for all the good input!!
 
caspian2 said:
Was wondering if anyone experienced similar situation and has any input before if get too far into trouble shooting.
Have a 2020 Jayco 5th wheel with DOMETIC DF series Furnace. When the temperature gets to the tight level on the thermostat, the furnace blower turns on fine, but the furnace does not light/kick in, so no heat. Blower runs for a while and then stops.
I have checked thermostat and LP line/supply and all Ok (all other LP appliances working fine).
Thanks My furnace has had a leaking collector box which has gone a very long time undetected. Mainly because of me being too cheap to have it inspected regularly. Anyways, the corrosion caused the blower to stop working, and the heat exchanger is rusted. Basically, I need a new furnace. I'm going to get some second opinions, but does anyone have advice on dealing with furnace companies, or know what a reasonable cost of replacement and furnace installation process? Sounds like it could be around $4500. Is that normal?
Click to expand...
My furnace has had a leaking collector box which has gone a very long time undetected. Mainly because of me being too cheap to have it inspected regularly. Anyways, the corrosion caused the blower to stop working, and the heat exchanger is rusted. Basically, I need a new furnace. I'm going to get some second opinions, but does anyone have advice on dealing with furnace companies, or know what a reasonable cost of replacement is? Sounds like it could be around $4500. Is that normal?

Thanks!
 
You are not sayin' what brand or model of furnace, or what size is required, or if it has easy access from the outside, or even if this is for a RV. :-/
I did a quick look on the 'net and you could get a furnace for under $2k.... but many variables.
Can you change it yourself? Save some $$$...
 
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