6 replies to this topic

[PNWtraveler]

2008 Hawk w/ Suburban NT-16SE Furnace

 

No issues with the furnace last winter, getting the rig prepped for winter camping and now the furnace will not put out hot air, the fan will run for about 30 seconds.

 

2 burner stove gas works 3 way fridge works on gas

 

I’ve done my tests with the truck engine running, being plugged into shore power and with only the battery, still the same results.

 

First issue - the Thermostat is not starting the fan for the furnace.  I plan to replace the original thermostat which should resolve this issue.  To workaround that issue I’ve removed one of the wires from its screw and touched it to the other wire and the fan kicks on. I'm assuming once that fan has kicked on the thermostat wouldn't be the cause of the below issue.

 

After about 30 seconds of the fan running the fan turns off without heat ever starting.

 

Found the small reset switch and switched that off for 10 seconds multiple times with no luck.

 

I removed the Electrode and it does not spark.

I removed the door to access the burner and did not smell any gas inside.

 

I’ve removed the furnace cover on the interior of the Hawk and located the Sail Switch in the back left corner of the furnace case and did the best job I could with a can of air to blow any dust away from the switch. When the fan starts up the switch does appear to move freely to engage, however I don’t know how I can tell if it’s fully engaged and hitting the place it needs to to start the propane.  

 

From reading other posts on other forums I think the Sail Switch is still the culprit unless I’m missing something else to test?

 

Is there a way to access the Sail Switch without disconnecting the entire unit and pulling it out of the cabinet? The furnace cabinet is surrounded by the rest of the wood cabinet so pulling the entire furnace seems like the next step?

 

Per the Parts list if I were to replace the Sail Switch it’s #230933 which has no been replaced by #525028

https://www.rvupgradestore.com/Suburban-Furnace-Sail-Switch-for-NT-12-16-20-S-SE-p/41-1321.htm

 

Thank you for any ideas on what else to test before pulling the furnace out.

 

 

[PokyBro]

In my experience, the sail switch can appear to function correctly, and even seem to be closed by plenty of air movement by fan, but still not complete the circuit so the solenoid will kick on the propane burner within the furnace. Sometimes they’re just defective. As cheap as sail switches are, I’d give it a try. I have an Atwood furnace I bought off Craigslist in new condition, but had this problem. Changed the sail switch and never reoccurred.

 

The furnace circuit board needs to know there is sufficient fan speed to safely ignite the burner so the flue won’t overheat. Without the signal, the burner won’t ignite.

 

Side note, I had a digital thermostat fail recently fail (threw an error code), and caused my system to not turn on. I went back to a old style manual thermostat, and will probably keep it that way.

 

Good luck!

[bajaphile]

Can you reach it with a bent coat hanger or something? If you can wiggle it around a bit first, then try to turn on the furnace, it might be enough for it to kick on. Also you can try parking on an incline so it can open up easier. Make sure you're fully charged up or even have the truck running so the fan is operating at max power. 

 

After replacing mine and still dealing with issues (it would only work when it was warm out, as the sail switch just didn't kick over enough when it was cold), I just added a small piece of metallic tape to the sail and now its worked 100% of the time since. 

[PNWtraveler]

Thank you for the advice.

 

I attempted to pull the sail switch all the way to confirm there is contact and the furnace will not kick on.  I've ordered a new sail switch in hopes that replacing it will fix the issue.

 

If anyone has experience with pulling out the furnace if they have any advice or anything important to note that would be very helpful before I dig into this once the new switch arrives.

 

Thanks

[Old Crow]

re: Furnace removal.... You may have already seen this but I'll go ahead and attach it here for future readers of the thread.  Furnace removal instructions are on page 6 of the Suburban RV Furnaces Service and Training Manual (2015 edition)

 

NT-12/16/20SE/SEQ

1. Turn off gas and power, then disconnect gas and power supply at the furnace. Label wires as necessary.

2. Remove the vent cap assembly by removing applicable screws.

3. Remove the cabinet front two (2) screws.

4. Remove the (2) two tie down screws securing the chamber to the cabinet.

5. Remove the furnace from the cabinet by pulling chamber outward completely to gain access to all controls and applicable parts.

6. To re-install, reverse this procedure.

7. Rewire applicable wires and perform a leak test on all fittings. Perform a drop pressure test.

 

Also-- I can't tell if you are hearing sparking attempts during starting attempts.  If you are hearing those, the problem is unlikely to be the the sail switch.  (Note- I see you say you removed the electrode and it doesn't spark.  Perhaps I'm misunderstanding that comment.)

 

Also from the service manual-- a troubleshooting flowchart and Sequence of Operations list from pages 29 and 30...  (There are multiple flowcharts and SOO lists in the manual. These say they're for the time-delay models and the parts list for the NT16SE shows it has a time-delay relay so I'm assuming these are the right ones...)

 

. 

 

Also- more technical documentation here

 

[PNWtraveler]

Thank you very much Old Crow.  

 

This will be very helpful!

[Old Crow]

The RV Works guy (Darren Koepp) just put up an interesting video about troubleshooting an apparent sail-switch problem with a Suburban NT-20SQ.  That furnace should be very similar to the NT-16SE in this thread.