Furnace - Burner troubleshooting

[balrgn]

1974, original furnace. Manual Light. The burner stays partially lit with the pilot on. This causes the furnace to cycle every 10 minutes or so due to combustion chamber temps.
New Regulator, full propane tank. All other gas appliances work with no issues.
Suspect a bad diaphragm in the inlet valve?

[PizzaChop]

I sort of feel stupid for suggesting it, as I know you've got a lot more experience restoring than I have, but have you considered replacing it?

A 34 year old furnace has probably served it's useful life some time ago, and the burner chamber probably has some thin spots from corrosion on the inside which you can't see.

I put a new NT 30 in my '73 Sovereign (and '72 Overlander) and it wasn't too difficult (as obviously you know) and the peace of mind is worth it all. It automatically lights when you move the thermostat (pretty cool compared to the original).

I mean, it's not like you couldn't make the original operational, but why waste your time, effort, and $$ when you'll still have a 34 year old furnace?

[HiHoAgRV]

When the furnace cycles on, does the stove level drop? I had a similar issue when I upgraded to the new style tanks. The hose nipple didn't fully push open the valve in the new tank. It was enough to light but after a minute it acted like a Freon orifice and froze up. By the time I got to the tank it had defrosted and the heater would relight. The only way I figured it out was when I noticed it would only do it on one of the tanks, the other was fine.

[balrgn]

HW heater and stove show no signs of loss of fuel with he furnace on. Good point tho, I will look at that again.

I have not as of yet pulled the panel off to see more of the area in there. From what I can see the chamber looks to be in very good shape. I just hate swapping out an entire unit if the solenoids valve is the only thing that needs to be rebuilt.

However I do have a new furnace web site book marked in my favorites if I decide to swap it out

[ticki2]

My vote is the solenoid valve , could be depris caught in it or just faulty . For safety reasons it must shut down completely ( which you already know ) . Might have a used one if you'ld like to try it , let me know .

[balrgn]

Originally Posted by ticki2

My vote is the solenoid valve , could be depris caught in it or just faulty . For safety reasons it must shut down completely ( which you already know ) . Might have a used one if you'ld like to try it , let me know .

Can you bring it this wekend, I'll bring some seal for the bottom of your door

[lewster]

Originally Posted by balrgn

HW heater and stove show no signs of loss of fuel with he furnace on. Good point tho, I will look at that again.

I have not as of yet pulled the panel off to see more of the area in there. From what I can see the chamber looks to be in very good shape. I just hate swapping out an entire unit if the solenoids valve is the only thing that needs to be rebuilt.

However I do have a new furnace web site book marked in my favorites if I decide to swap it out

Sounds like a gas supply problem to me. Either the solenoids are no longer opening the valves sufficiently to provide the required flow of LP, you have a blockage in the valves themselves, you have a blockage in the brass orifice that controls the flow of LP to the burner tube, or the internal regulator in the gas valve is not properly set. It should read 11" water guage with a manometer.

The last suggestion happens very frequently, but I would definitely check all of the above if saving your vintage furnace is your priority. Have fun!

[ticki2]

Originally Posted by balrgn

Can you bring it this wekend, I'll bring some seal for the bottom of your door

Will do .

[balrgn]

Still on the fence for the Repair vrs Replace.

Thanks for the part Tiki2

Are the new styles, auto igniting, a direct wiring replacement from one with a manual light?

[lewster]

Originally Posted by balrgn

Still on the fence for the Repair vrs Replace.

Thanks for the part Tiki2

Are the new styles, auto igniting, a direct wiring replacement from one with a manual light?

The DSI ignition furnaces need 4 wires: 2 thermostat (which you have now) and a +12VDC and -12VDC. Power to the igniter board is supplied by the 12VDC (which you need on any furnace) which in turn controls the blower, ignition and the gas valve. The t/stat is the on/off control.

It should just wire right in!

[Fyrzowt]

Lew,
I appreciate your helpful posts such as this. You always seem willing to lend assistance without the "attitude" that we sometimes see elsewhere.
Thanks!
Dave

[balrgn]

Originally Posted by Fyrzowt

Lew,
I appreciate your helpful posts such as this. You always seem willing to lend assistance without the "attitude" that we sometimes see elsewhere.
Thanks!
Dave

Me TOO!

New one on order, the more I thought about it the safer it is to just go new.

I'll keep ya posted on the install

[PizzaChop]

Don't be a hero, just go ahead and replace it. (You'll be so glad you did!)

[Lumatic]

Your furnace other than not having a circuit board has the same basic parts as newer furnaces. The parts are limited but the permutations of possible combinations responsible for the problem are geometrically progressive (and could croak you) including: dirt, mud daubers in combustion chamber, leaks in the combustion chamber, thermocouple, anti sail switch, and time limit switch (not an inclusive list).

You will also have a lot of trouble finding anyone to work on them, both because most techs don't know about the oldies and if they do are prohibited by their liability policies. If you do find someone, a lot of parts are difficult if not impossible to find.

I fiddled with mine for a while and gave up and got a new one. It was an educational experience, I'm glad I did, and I know a lot more about what makes a furnace tick. But, I could have save a lot of time by not messing with it, biting the bullet and replacing it.

[lewster]

Thanks guys!

I have a sticker on the back window of my service van that reads "Attitude is Everything". I certainly believe that to be true!

It's always my pleasure to add something of substance to a thread when I can (and sometimes just for a little humor also ).

[balrgn]

Got the old one one, I did bite the bullet.

Already kinda glad I did, It has been take out in the past, the quality of the reinstallation leaves a bit to be desired. I found no mounting screws to hold it in place, only the 2 to keep it fastened at the exhaust. Wires were twisted back together, not all with wire nuts.

Other than that it was a 15 minute task to remove. This will give me a chance to straighten things up under there


Thanks for the encouragement!

[bobandcarla]

Originally Posted by balrgn

Got the old one one, I did bite the bullet.

Already kinda glad I did, It has been take out in the past, the quality of the reinstallation leaves a bit to be desired. I found no mounting screws to hold it in place, only the 2 to keep it fastened at the exhaust. Wires were twisted back together, not all with wire nuts.

Other than that it was a 15 minute task to remove. This will give me a chance to straighten things up under there


Thanks for the encouragement!

Twisted together? Kinda makes you wonder how some people think. I mean, your sleeping back there and the furnace is running and what if something happens? Yikes!!!
I'm glad you pulled it out, Bro. We can't afford to have something happen to you guy's!

[balrgn]

New Furnace was delivered today. The foot print is completely different. So, I have some fabricating to do. The unit will need to be mounted 90º, intake/exhaust mounting will require a plate mounted on the outside to take up from the original hole mismatch.

Put temp power and fuel to it, it started right up, quiet with good flow of heat!!!

[PizzaChop]

The foot print is completely different. So, I have some fabricating to do. The unit will need to be mounted 90º, intake/exhaust mounting will require a plate mounted on the outside to take up from the original hole mismatch.

Did you go with the NT-30?

[balrgn]

Hydro Flame 8012