RV heater troubleshooting

The built-in propane heater in my camper has me stumped. It tries to start when the thermostat is pushed up, but just never lights. Hoping someone here has an idea to try before I start buying parts or a new core.

The heater is an NT-20SEQ. Everything checks out: thermostat sets it going, blower runs, sail switch moves and seems to click, igniter sparks (visually confirmed), I can smell propane at the outlet when it's trying to light. It just never lights. I've cleaned it, checked for blockage at the gas port, tried gas line purge tricks (run the fridge and the burners for a bit to ensure no air 8n the lines), but nada.

Could it be the control module? My brain tells me "it has air, fuel, and spark", but is there something in the module that could be preventing it from lighting off? It never gets a flame at all.

A new core is $400, a new control module is $100.

I'm baffled...

I have put a dinosaur control module in every appliance in my RV.   They have fixed nearly every issue (my fridge needs an "eyebrow" switch that's finacky).   My furnace seemed to be doing the same thing as yours.   It would try to start but never seemed to get actual flame.   I replaced the board and it worked.  I believe it was the solenoid gas valve wasn't getting enough signal to open from the OEM board that apparently had an issue. 

I can't guarantee that it will work.   But I'd probably go there next.

Second on the Dinosaur board.  I had the same problem on mine and the board cured it.  The down side - at least for mine - is that they put the stupid control board in a place that requires the furnace to be removed from the RV. 

wae said:

Second on the Dinosaur board.  I had the same problem on mine and the board cured it.  The down side - at least for mine - is that they put the stupid control board in a place that requires the furnace to be removed from the RV. 

Thanks for the tips nocones and wae. Checking on sources for the Dinosaur board.

I'm in the same situation that the whole unit has to come out to get to the module, but it's not too terrible.

In reply to CLH :

I bought mine from Amazon 

Something like this one you have to go to the dinosaur website to get the exact right model for yours or they have a "universal" one if they don't make a specific one.  

https://www.dinosaurelectronics.com/index.htm

Mine is an Atwood and thankfully the board is removable behind the removable exterior furnace cover.  

I've bought one from Amazon but I needed one same-day once because we were getting ready to leave when suddenly one of the appliances took a dump on me.  I was able to get one from the parts counter of one of the local RV places, so they are stocked locally in some places at least.  I think all I have are the universal ones, but it's been too long to remember.

Ordered on Amazon. Fan50PlusPins was the right one according to multiple sources I came across (PDX RV has all the parts diagrams and x-ref stuff online). Thanks for the pointers. Fingers crossed!

Well...got the new board today, did the installation, triple checked everything, and still no dice. I guess it's either debris in the line or a faulty gas valve. I can smell gas at the exhaust port outside when it's trying to light, but clearly it's not enough gas to light up. Spark is good - can see it very well through the viewport and checked all the gaps. Dang it.

Edit to add: I did confirm the LED on the ignition board when testing. LED was green when thermostat moved to start the cycle, then was red when supplying power to the gas valve solenoid, as it should. So at least according to the board, all components are good at least up to the gas valve.

Chiming in late. 

Are you able to get a BBQ Lighter in to the burner? Is a larger heat source able to achieve ignition? 

Gas smell doesn't mean ample fuel flow. 

I'd be testing gas valve next

Swapped out the gas valve with a new one, and still no joy :-(

I'm pretty well stumped at this point. As a last chance option, I may go get a full propane cylinder just to see if the problem is low pressure from the current one that's about 1/3 to 1/2 full. The fridge and stove both work, so I really don't think that's it, but maybe...

So the new board is definitely clicking open the gas valve and firing the spark?  I'd think that even a low gas cylinder would eventually get you a little bit of a poof from the accumulated gas.  I'd second trying to get a secondary flame source in there to see what it would do.

The mystery continues. At this point I've pretty much decided that we just won't have propane heat in the camper.

Confirmed that a fresh bottle doesn't help. Still doesn't light. Fridge, burners, and water heater all fire right up. I disconnected the lines, blew them out with air, and verified no blockages.

As a last grasp at straws, I sprung for a replacement core through HD. It was ~$400 with mil discount, and was returnable, so low risk. I wasn't sure whether I wanted it to work or not work. If it worked, it would be a $400 fix. If it didn't work, it would mean it's got to be something with the camper gas system.

Well my friends...it didn't work.

The *only* thing I can see that's maybe something that would contribute to the issue is that where the gas line comes in under the fridge, it has a sizable radius bend in it, maybe 6-7" radius, looping up, over, and then back flat into the furnace valve. I would think the gas pressure would push any trapped air in there through, but maybe not?

I'll keep trying it every now and then to see if it ever fires up, but I've otherwise given up.

Do all the other propane appliances work right?

NY Nick said:

Do all the other propane appliances work right?

Everything else works perfectly.