Suburban furnace problem

[Maxfane]

Hi all, I have a 1975 Excella 500 with its original suburban furnace in place. It goes through all the processes of lighting as it should but fails to stay lit!
Hear comes out of the vents and after around a minute I can hear a click and the flame goes out, the fan stays on but just gets cooler until all the heat has gone. I have cleaned out the burner, reset it as in the service manual and still no joy.
The room stat seems to be ok, anyone got any ideas! Thanks

[Condoluminum]

There is story in current Blue Beret about clamping 12V electrical connectors being loose and causing similar failures.. You might open up panel below and see if any of the wire junction connectors have any looseness in them.. Look especially at any "T" wire junctions.. Apparently in article Atwood furnace had wrong size connectors (too large for wire diameter/gauge). though could have been wrong size supplied at Airstream during assembly.. They are called IDC push-on connectors, and story is on page 26 of November 2013 Blue Beret.. You may be able to view it online at WBCCI, or I could scan it if needed.. Usually shut off of heat linked to either low gas pressure or electrical circuit breaks to propane valve, which shuts it off and then eventually shuts down furnace... In the article, shutdown was intermittent, and usually more prevalent when it was coldest...

[Aage]

Sail switch? Thermocouple?

But really, time to face it: your furnace has reached a ripe old age and may well need replacing. These things rust out internally and become very dangerous.

You'll sleep a lot better if you put a new one in...

[Inland RV Center, In]

Originally Posted by Aage

Sail switch? Thermocouple?

But really, time to face it: your furnace has reached a ripe old age and may well need replacing. These things rust out internally and become very dangerous.

You'll sleep a lot better if you put a new one in...

6
I ten to the 6th power, ( 10 ) second that.

Andy

[Mike Leary]

Originally Posted by Inland RV Center, In

6
I ten to the 6th power, ( 10 ) second that.

Andy

We just did the same thing after spending too much time and money having "techs" pull it and screw around with it. Sure is nice to hear a brand new fresh furnace come on in the morning!

[Lumatic]

Would you use a 38 year old appliance that burns propane and makes carbon monoxide in your house with your family?

[TG Twinkie]

I am sure there are many people out there that are still using the original oven and cook top.
There are many people out there with 30 to 40 year old furnaces running in there homes.
Doesn't mean it's OK, but it happens.
I would never sleep in any trailer, no matter what age it is, without a window open when the furnace is on.

[Maxfane]

Many thanks all, the problem I have is my trailer is based in the uk and it is not easy to find someone to look at my existing furnace or to acquire parts. Maybe a new furnace is the way forward.
What is the easiest and best furnace to fit as a replacement?
I had enough of a fight getting the old one out to clean it up, due to rust on the runners.
Thanks Max

[pattydoug]

Originally Posted by Lumatic

Would you use a 38 year old appliance that burns propane and makes carbon monoxide in your house with your family?

Yes. If proper periodic maintenance is performed and inspected each year, older units can be, and many times are, as safe, if not more so, than new ones.

The problem with this one is most likely a $16 limit switch that is failing and is a simple repair, or even a loose connection on the control board. If the burner, and the combustion chamber are intact there is no reason to dump a good furnace. RV furnaces are basically the same as they were 40 years ago.

We replaced the one in our '86 Avion this last spring because the combustion chamber had significant rust, effecting the integrity of the chamber. The new, direct replacement, for all purposes, looks and operates just like the old, 27 year old unit, except it is slightly lighter.

We also have the original Swedish made Dometic fridge, and there are NO RECALLS on it, as there are on all the new ones. I feel safer with this old 1303, than I would with a new one.

[inTransit]

I had the same problem and it was the gas valve solenoid that went bad. If you have an older NT-22 or NT-32 the parts typically have to come from salvaged units. I upgraded but Ill never scare or insist to anyone they have to upgrade an appliance. If the furnace has had all recalls performed and been cleaned and inspected by a professional technician, it is not unreasonable to expect continued life from it.

Ill tell you I bought a much newer heater and aside from the bad part they were hardly distinguishable. Other than the modifications to my trailer I had to make to accommodate that new furnace of course.

[Lumatic]

It has been my experience that finding a tech who is willing to work on a 30+ year old furnace is like getting milk from a boar hog. ( I tried) Even if you can find a service person who is knowledgeable and willing by the time you pay for the repair you have spent a good chunk of what a new furnace will cost. Palomino RV sells NT 30 and NT 35 for about $400.

So the question is are you expert enough to be confident in your abilities to diaganose an DIY?

[featherbedder]

My sub. furnace was not old but A.S. had recall because of safety prob. Prob. is I pur. new from A.S. dealer never informed by A.S. of recall Also registered with A.S. Several years after recall I replaced because carbon monoxide in trailer [this was reason for recall] I only found out about recall from friend that used to wrk at A.S. fact. when I called they said couldn't help me, so much for cust. serv.

[blkmagikca]

I had a similar problem with my furnace. When I was having it serviced at JC, the tech actually measured the pressure of the propane (most gas technicians will have this equipment) and found it to be very low. As I recall it should be "11 inches of water", and mine was around 8. All that the tech needed to do was to adjust the output pressure of the regulator and it has worked flawlessly since then.