1977 60017 DuoTherm Furnace is making my brain implode

Zed · 10-08-2022, 04:05 PM

Hey all!
Total newbie here. I've spent a pile of time in the forum and on the interwebs but haven't been able to find a solution to my problem. I'm hoping you can help me out.

I'm the brand new owner of a 1979 Sunline. I *believe it's a 17 1/2 SB but all the markings and plates were painted over or removed so it's been a bunch of guesswork.

I've been trying to get the furnace (1977 - 60017) to work but the pilot light keeps going out when I try to switch to the ON position. From my SCOC searches, it seems it might be the thermocouple? But I honestly have no idea.

1. How can I tell if it's the thermocouple? What tests do I need to run to diagnose this?
2. If it is the thermocouple (or I need to clean the thermocouple and pilot), how the heck do I access those parts?
3. There's a little brass screw on the assembly that's labelled vent. What position does this need to be in? It's currently tight closed.
4. Same question for the pilot adj...

Whew. Thanks in advance. I'm up to my eyeballs in questions right now.

johnmanna · 10-09-2022, 09:14 AM

It sounds like there could be air in the line .Also could be a spider webb blocling the orfice.TRU TO VACUME THE AREA .they make a speal tool to ream it with but sometimes vacumiing will work Atherwise you will need to repace it

Zed · 10-09-2022, 11:10 AM

Thanks @Johnmanna!
That's a good suggestion.
How do I access the parts to vacuum them? (or ream them if I decide to go that direction)

Tinstaafl · 10-09-2022, 12:08 PM

If you light the pilot, keep the button pressed for 15-30 seconds to ensure the thermocouple's heated up, and then let go of the button without doing anything else, does the flame stay lit? If it does, the thermocouple is working properly.

Zed · 10-10-2022, 05:00 PM

Thanks @tinstaafl.
I've already done this numerous times - increasing the amount of time I've held the button down - up to nearly 2 minutes. This is why I think it might be the thermocouple.

Ultimately, I can get the pilot lit but it doesn't stay lit for long after I let go of the button.

Quote:

Originally Posted by Tinstaafl

If you light the pilot, keep the button pressed for 15-30 seconds to ensure the thermocouple's heated up, and then let go of the button without doing anything else, does the flame stay lit? If it does, the thermocouple is working properly.

Tinstaafl · 10-10-2022, 05:27 PM

I think you're thinking right. As long as the pilot flame is hitting the tip of the thermocouple decently (if you can see the pilot, you should be able to see the thermocouple), it should be putting out enough voltage to hold the valve open.

That's about 25-30 millivolts, just in case you or someone you know is nerd-savvy enough to put a meter on it and measure its output. But truth be told, I've seldom bothered with doing that. If it's obvious it's getting good heat but not doing its job, 90% of the time a replacement will fix the problem. They're cheap enough that it's NBD to give it a shot. The other 10% would be a malfunctioning valve--that's pretty rare.

Obviously, that needs to be corrected before you even bother with turning the main burner on to see if/how that works.

Your challenge will be to locate a replacement thermocouple with the appropriate form factor. Here's hoping that Google is your friend.

Zed · 10-11-2022, 07:51 AM

Yay, this is great information @Tinstaafl, thank you!
So - the big question then is how the heck do I get the thermocouple out of this beast? Whether that's to vacuum or ream it or replace it?
In Google I trust...

Quote:

Originally Posted by Tinstaafl

I think you're thinking right. As long as the pilot flame is hitting the tip of the thermocouple decently (if you can see the pilot, you should be able to see the thermocouple), it should be putting out enough voltage to hold the valve open.

That's about 25-30 millivolts, just in case you or someone you know is nerd-savvy enough to put a meter on it and measure its output. But truth be told, I've seldom bothered with doing that. If it's obvious it's getting good heat but not doing its job, 90% of the time a replacement will fix the problem. They're cheap enough that it's NBD to give it a shot. The other 10% would be a malfunctioning valve--that's pretty rare.

Obviously, that needs to be corrected before you even bother with turning the main burner on to see if/how that works.

Your challenge will be to locate a replacement thermocouple with the appropriate form factor. Here's hoping that Google is your friend.

Tinstaafl · 10-11-2022, 08:41 AM

I've never met an assembly I couldn't tear apart.

If you can positively identify the make and model, you may be able to find a parts breakdown for it in our Files section (or elsewhere on the internet). That can help quite a bit with seeing how things are assembled.

Failing that, just possibly if you can ID exactly what model your camper is, one of the old-timers here might know what furnace it used. The Files section also contains a boatload of Sunline brochures from over the years; looking through them for your layout can help with that.

Good luck!

Zed · 10-11-2022, 08:46 AM

LMAO that's awesome.
All the info is on the plate. I'll look for a parts breakdown and see what I can do.
Thanks for your help. No doubt, I'll be back.

Quote:

Originally Posted by Tinstaafl

I've never met an assembly I couldn't tear apart.

If you can positively identify the make and model, you may be able to find a parts breakdown for it in our Files section (or elsewhere on the internet). That can help quite a bit with seeing how things are assembled.

Failing that, just possibly if you can ID exactly what model your camper is, one of the old-timers here might know what furnace it used. The Files section also contains a boatload of Sunline brochures from over the years; looking through them for your layout can help with that.

Good luck!