Furnace not turning on

[Cort]

One tank ran dry, so I moved to the other tank—the furnace did not turn on. Then I filled the empty tank—the furnace will still not turn on. The pointer is pointing to the full tanks (both are full now) and I've moved the thermostat from on to off several times. 

 

Any ideas?

 

(By the way, I searched for "Furnace does not turn on", "Gas does not turn on and no heat and got posts on axles and other things). 

[Rolind]

Will the range light? After changing out tanks or after prolonged storage, we sometimes have enough air in the lines that the furnace has a difficult time lighting or won’t light at all. I will usually then light the range briefly to at least purge the air from the lines to the range top. Usually the furnace will then light.

[Ronbrink]

If a tank valve is opened too quickly the flow of gas can be shut down. Turn the valve slowly at first, but only enough for gas to begin to flow; then wait several seconds before turning the valve fully open. It is always good practice to purge the lines as @Rolind suggests in the manner described.

Edited Wednesday at 12:56 PM by Ronbrink

[Cort]

2 hours ago, Rolind said:

Will the range light? After changing out tanks or after prolonged storage, we sometimes have enough air in the lines that the furnace has a difficult time lighting or won’t light at all. I will usually then light the range briefly to at least purge the air from the lines to the range top. Usually the furnace will then light.

Thanks! At first the range would not light but after a couple of trys it did. The furnace appeared to click on briefly (the fan came on - cold air) and then stopped. 

[Cort]

1 hour ago, Ronbrink said:

If a tank valve is opened too quickly the flow of gas can be shut down. Turn the valve slowly at first, but only enough for gas to begin to flow; then wait several seconds before turning the valve fully open. It is always good practice to purge the lines as @Rolind suggests in the manner described.

Thanks for the tip! 🙂

[jd1923]

5 hours ago, Rolind said:

I will usually then light the range briefly to at least purge the air from the lines

Agreed, this should be standard operating procedure. My wife does this by habit every time she asks me to turn the gas on. Then we switch fridge to LP and the hot water heater on LP (when boondocking).

I've never had to turn the gas on slowly, did not realize there is an internal safety valve.

Did you check the fuse in the 12V fuse panel?

[Galileo]

I had a similar issue a few days ago. 

Ran out one tank, furnace stopped lighting. (It quit trying after two or three failures to light.) I shut off the empty tank, turned on the full tank, and flipped the tank selector to the full one. Indicator turned green. Furnace lit right off.

Next morning, no heat again. Checked the tank. Indicator on selector was red. Flipped it back and forth, no joy. Closed the full tank valve and reopened it. Voila! Indicator green, all is right with the world. Just weird though.

BTW - I never turn both tanks on. I operate off of one until it’s dry. Then switch. I just don’t want the automatic switchover to do its thing and ME not realize I’m eating up my reserves!

Only had to do the purging of air using the cooktop once. I think the Truma WH instructions mention that fix for a non-lighting condition. 

[Ronbrink]

59 minutes ago, jd1923 said:

I've never had to turn the gas on slowly, did not realize there is an internal safety valve.

Yeah, opening the cylinder valve too fast can trigger a safety feature inside the tank; specifically an ‘excess flow valve’, at least as best I understand it.

[Ronbrink]

1 hour ago, Galileo said:

Only had to do the purging of air using the cooktop once.

I installed GasStop valves on each tank, which has an integral purging feature. Also great for use with gas grills, fire pits, etc., when auxiliary lines are connected to a spare tank or directly to one of the Oliver tanks

[Geronimo John]

1 hour ago, jd1923 said:

I've never had to turn the gas on slowly, did not realize there is an internal safety valve.

When a tank is empty likely an appliance was on.  When the propane gas stops flowing, the line pressure is equalized to atmospheric.  With connection of a fuller tank, and opening the valve there is a surge of flow.   The OPD thinks there is a line rupture (Too high flow) and cuts off the flow. 

Until now, I had always thought I had to disconnect the hose from the tank to reset the OPD.  Apparently not according to AI.  AI says just turn off the valve.  Here is more AI thoughts.  (LOL that sounds weird.... AI Thoughts???):

• Safety feature:

  The OPD is designed to protect against dangerous situations like rapid gas release, which could occur if the tank valve is opened too quickly or if there is a sudden high demand for propane. 

   
• How it works:

  When the flow rate exceeds a predetermined limit, the OPD valve within the tank automatically closes, restricting the gas flow. 

   
• What to do if this happens:

  If your propane tank stops flowing gas due to high demand, simply turn off the tank valve for a few seconds and then slowly open it again to reset the OPD. 

Other potential reasons for low gas flow from a propane tank:

• Low tank level: As the propane level in the tank decreases, the pressure also drops, leading to reduced gas flow. 
   
• Faulty regulator: A malfunctioning regulator on the tank can also limit the gas flow. 
   
• Cold weather: In cold temperatures, the vaporization rate of propane can be reduced, causing lower gas pressure. 
   
• Improper connection: A loose or damaged hose connection to the tank can restrict gas flow. 

GJ

[Rolind]

Some heaters, maybe all have a feature that will stop further attempts    to ignite after a certain number of failed attempts.  Our is three.  If this happens it can often be reset by turning the heat off and then back on.

[Galileo]

2 hours ago, Geronimo John said:

AI says just turn off the valve.  Here is more AI thoughts.  (LOL that sounds weird.... AI Thoughts???):

I don’t trust AI interpretations. Seems like everybody is trying to ram AI down your throat. Google returns an AI “synopsis” ahead of actual search hits, Yahoo Mail was summarizing my emails. I shut that off. Fully half the time it was getting it wrong - often exactly wrong.

AI just grabs web content. That could be from sponsored sites, or crowdsourced sites that may or may not even be correct. 

I tend to skip right over the AI summary, blow past the sponsored sites, and scroll down to a source that at least sounds objective and reliable.

 

(I had to turn off the valve, AND remove and reattach the POL connector to get the tank selector to show green. )

[Cort]

6 hours ago, Galileo said:

I had a similar issue a few days ago. 

Ran out one tank, furnace stopped lighting. (It quit trying after two or three failures to light.) I shut off the empty tank, turned on the full tank, and flipped the tank selector to the full one. Indicator turned green. Furnace lit right off.

Next morning, no heat again. Checked the tank. Indicator on selector was red. Flipped it back and forth, no joy. Closed the full tank valve and reopened it. Voila! Indicator green, all is right with the world. Just weird though.

BTW - I never turn both tanks on. I operate off of one until it’s dry. Then switch. I just don’t want the automatic switchover to do its thing and ME not realize I’m eating up my reserves!

Only had to do the purging of air using the cooktop once. I think the Truma WH instructions mention that fix for a non-lighting condition. 

Thanks Galileo and everyone - I learned a lot :). The indicator switch turned out to be the clue - I just had to keep closing and opening the tank valve until it showed green - and now I know to open slowly and am prepared for the next time 🙂 

Edited Wednesday at 11:44 PM by Cort

[Geronimo John]

On 3/5/2025 at 11:46 AM, Galileo said:

(I had to turn off the valve, AND remove and reattach the POL connector to get the tank selector to show green. )

Me too.  My point exactly.....

On 3/5/2025 at 9:07 AM, Geronimo John said:

Until now, I had always thought I had to disconnect the hose from the tank to reset the OPD.  Apparently not according to AI.  AI says just turn off the valve. 

For the last 59   27 years we share the same procedure.  Off, Disconnect, Reconnect, On, Bleed line.  But I did not want to contradict another owner as I have no idea how his regulator works.  But AI says........

CRAZY HORSE Fact Check:  REVISED:  OPV's were only introduced in 1998.  

Edited Friday at 04:26 PM by Geronimo John
CRAZY HORSE Fact Check

[Galileo]

I didn’t know that the “recent” change to LP tanks (whatever you call that overfill prevention device - when the shape of the valve knobs changed, and propane places stopped rifling the I’d ones)  did anything except prevent it from being filled to more that XX percent of full by volume to allow for expansion. 
 

I think the POL (“Press-to-lite”) coupler/valve is what did the shutoff if there’s too much flow. I could easily be wrong, but I remember even “old” tanks would shut off with high-flow devices. (I have a 140,000 BTU “King Kooker” burner that was good at this.)

[jd1923]

On 3/5/2025 at 2:46 PM, Galileo said:

I don’t trust AI interpretations...

(I had to turn off the valve, AND remove and reattach the POL connector to get the tank selector to show green. )

Yep, AI will only allow the young to be lazier than how they've been brought up!
Teaching my class this week, one new student logged into the Zoom meeting with an AI interpreter of some kind. I'm willing to bet, that she by counting on technology, will learn and retain far less than the average student! Give me a break! "Just Say No" when anything pops up on your screen!

I've never noticed anything colored green on the tank selector. Am I missing something or perhaps our older hull is different. I turn it left until the first tank is empty or near empty as shown on our Mopeka sensor, then I switch to the RH tank. Never noticed a color, or maybe I'm colorblind!

[Galileo]

On 3/7/2025 at 2:24 PM, jd1923 said:

 

I've never noticed anything colored green on the tank selector. Am I missing something or perhaps our older hull is different. I turn it left until the first tank is empty or near empty as shown on our Mopeka sensor, then I switch to the RH tank. Never noticed a color, or maybe I'm colorblind!

Sorry if I’m using the wrong term or if my not including a picture is making it less obvious.

Whatever that Thingamabob that connects the two tanks together and has a little lever that swings left and right is called. Ours has a little indicator that shows 2 green “sectors” if the tank is supplying gas. I think it shows red if no gas (but it might show black - I’m 400 miles from the trailer at the moment).

Anyway, it’s the contraption that is supposed to automatically switch tanks when the primary one runs out of gas. I never use that function as I don’t wanna end up with both tanks empty because it switched and didn’t tell me. 

If the little indicator is dirty, or you are just viewing through the round access port of the front of the propane enclosure, you may never see the indicator. (So you may not want to deviate yourself colorblind just yet!)

[topgun2]

6 hours ago, Galileo said:

Thingamabob

= Regulator.

7 hours ago, Galileo said:

has a little lever that swings left and right

if you mean to NOT have the automatic change over feature of this Regulator engaged then this "little lever" should point to the tank that you would like to use.  When that tank is empty then simply move the "little lever" such that it points to the other tank.

Bill