Suburban Heater Problem

[EZinColo]

Howdy,
New member - just signed up. We have a 1998 GS Conquest 21' with a Suburban propane heater. On our last two trips to the mountains the heater didn't go on. The fan starts when activated by the thermostat but then stops after about 10 seconds. I'm assuming the burner isn't lighting?
We live in Colorado and the heater works in our driveway at home (5280 ft altitude) but these past two trips were up to ~10,000 ft. The repair shop we use said they've heard of altitude being a possible cause but they couldn't replicate the problem (they're at same altitude we are).

Has anyone heard of altitude problems and a solution? or any other suggestions about how to troubleshoot this?

Thanks for your help.
Eric

[THenne1713]

YES, have read several similar complaints, not much you can do that I have read? If you can get GEN to run OK at that altitude, *which might also be a challenge?), you might consider electric heat, but recall GEN Power rated also degrades w/ altitude, so more limits do apply

[EZinColo]

Thanks for the reply THenne1713!
We don’t have any problems with generator, it works all the time, everywhere. Hadn’t thought about electric heater (not ready to give up on this, ya know)
We just got back from a trip to Steamboat Springs, altitude ~8000 ft. The heater worked the second night there but NOT the first night - at the same campsite).
I’m gonna check some other RV user web sites, not just Gulf Stream, since they all use propane heaters.

Thanks again for your input. I’ll be sure to post my progress with this.

Eric

[RY469]

When the furnace gets told to turn on by the thermostat, the fan comes on (as yours does) then the "sail switch" has to be made by the fans airflow. If made, the gas will ignite, etc . . . If the sail switch does not activate, the furnace will shut off (as yours does). The sail switch is a little micro switch mounted on the air tube, with a metal "sail" on the arm inside the air tube that pivots. You can see it if you pull the cover off the outside of the heater. Make sure you have no blockages in your air ducts (wasp nests etc). Then check your sail switch. Maybe the airflow is restricted enough that the thinner air makes a difference? Hopefully this points you in the right direction.

[EZinColo]

Master Chief,

I'll check that out next week.
This has gotta be something there's a fix for since the mountains are a popular RV destination 👍
Being the son of a career Marine, I seem to have been getting help from the Navy my whole life (staring with a Navy Dr at Camp LeJeune a LONG time ago)
Thanks for continuing that tradition. 😉

I'll keep you posted on this issue.

All the best,
Eric Slack

[EZinColo]

Hello Chief
Got a a chance to dig into this again and I’m not seeing the sail switch you mentioned. The top tube in the phots is the outside air intake to the furnace - nothing blocking that. The bottom tube is much longer. I shined a light into it and tried to get a shot. Tough to see in the picture it’s clear as far as I can see. The cold air return is removed in the other pic - nothing to see there but the back of the unit.

Am I missing something?

Thanks
Eric

[Chuck v]

Lots of videos on-line showing this -- here is a typical one:
https://www.google.com/url?sa=t&rct=...l&opi=89978449


Chuck

[RY469]

Your middle image shows a black square switch (with white sticker on it) that has a black and a red wire attached. Look at bottom side, you will see metal arm that goes into the air duct of the fan. There's an enlarged portion of the metal arm inside there called the "sail." If you push up on the arm, you will hear the click of on-off of this micro-switch. SO, all that said, you can ensure the switch is made when the furnace is trying to start (fan starts running). Either visually or by human intervention. Then the igniter should click and the spark should occur in the burner. Just be mindful you are dealing with explosive propane if you choose the later (human intervention). Does this help?

[THenne1713]

The IGNITER is also the THERMOCOUPLE (on the refrig, maybe same on furnace?) and without that signal, it will turn gas solenoid back off also. Even a spider web can divert the flame, but low battery, sail switch, poor connections= low voltage at furnace, LPG regulator malfunction, tank valve not fully open, (several DW have paid RV Techs $100+?) to find tank valve was just cracked open when they were told differently by DH ?)

[EZinColo]

Thanks for the replies Chief and THenne1713,

I've ordered a new sail switch, should be here in a day or so. I toggled mine and it *might* have felt a little stiff - but for $6 or so, I'll replace and go from there.
I'm still a little suspicious how thinner air (8500 ft vs 5280 at my home) could affect how that switch operates.
I'll let you know how it goes.

Appreciate your help,
Eric

[EZinColo]

I put the new sail switch in and it DOES move more smoothly then the old one. We’ll have to wait until we go back up in the mountains to see if it works at altitude. I’ll post and update at that time.
Thanks for the help
Eric