No Heat From Furnace

[langeraf]

Not getting any heat from the furnace. It turns on for 5 min and runs/blows, but the air does not warm and then it shuts off. It seems like perhaps it is not igniting. Any ideas?

[Old car]

Is your propane on? We turned on our furnace one time but forgot to open the valve on the propane tank. Ran a couple of minutes and kicked off.

[LadyWindrider]

Hate to say this, but do a search on here for furnace. Plenty of threads with furnace problems, trouble shooting info, explanations of how it works, what has to happen when,
And yes, you will need the propane on, and light the stove to make sure it is working, before you try the furnace.

Since you didn't say how old the unit is, is it still under warranty?

[TURBS]

Do you hear a clicking sound right when it comes on?

[Herk7769]

This problem has a few causes:

In order of easy to check and fix to hardest:

1) No propane to furnace - make sure the stove burners all run at the same time at full blast. If not: close the tank valves; wait 2 minutes; then crack the primary (selected) tank slowly taking a slow 20 count from CLOSED to full OPEN. No kidding here; count and turn SLOW.

2) LOW DC VOLTAGE in camper - This will cause the blower to run too slow to press on the sail switch with air flow which must be closed to apply power to the gas solenoid valve, letting the burner light. - Measure the DC voltage at the battery. It must be above 11.8 volts to spin the fan fast enough to close a functioning sail switch. Find and fix the cause of the low voltage.

3) LOW DC VOLTAGE at the Furnace - This will cause the blower to run too slow to press on the sail switch with air flow which must be closed to apply power to the gas solenoid valve, letting the burner light. - Measure the DC voltage at the main board. It must be above 11.8 volts to spin the fan fast enough to close a functioning sail switch. Find and fix the cause of the low voltage.

4) Fan running too slow; voltage good - This will cause the blower to run too slow to press on the sail switch with air flow which must be closed to apply power to the gas solenoid valve, letting the burner light. - Find the cause of the slow running fan.

A) Mud Dauber Nest or DIRT in the fan itself - CLEAN FAN.

B) Bad motor - Replace Motor - This is difficult but can be done by a handy person. NOTE - THIS SHOULD BE LAST

5) Bad Gas Solenoid - Replace Solenoid - This is difficult but can be done by a handy person. WITH THE GAS SHUT OFF - It can be checked by applying 12 VDC to the solenoid directly and see if it clicks and you smell the gas that was trapped in the line.

6) Clogged gas nozzle - Replace nozzle - Examine the gas nozzle. You will need to remove the shroud. If obviously clogged buff gently with steel wool or replace. NEVER insert anything inside the hole (this will enlarge it and cause an unsafe condition).This is difficult but can be done by a handy person.

7) Bad Control Board - Replace Control Board - If, when the furnace is calling for heat, the fan is running like a champ and you smell gas but it does not light; replace the control board. Dinosaur Electronics Home. High quality circuit boards for RV appliances.

8) Bad Sail Switch - Replace Sail Switch - Pretty hard even for a handy man.

[Superchief]

I have had this issue twice, once last year and jus the other day. Both times the furnace "locked out" electrically from trying so many times. When it would not start last year, I took it to the dealer. Wouldn't you know that it started for them as soon as I got there. They checked it out anyway and found nothing. They said it must have reset it self. Okay...... The other day, it also would not put out heat. Remembering last year, I unplugged the entire motor home and let it sit for about 30 minutes, thinking this would give it enough time to reset itself. As soon as I plugged it back in, it started the first time with heat. I was plugged into a 30 amp system at the time.

[Herk7769]

Originally Posted by Superchief

I have had this issue twice, once last year and just the other day. Both times the furnace "locked out" electrically from trying so many times. When it would not start last year, I took it to the dealer. Wouldn't you know that it started for them as soon as I got there. They checked it out anyway and found nothing. They said it must have reset it self. Okay...... The other day, it also would not put out heat. Remembering last year, I unplugged the entire motor home and let it sit for about 30 minutes, thinking this would give it enough time to reset itself. As soon as I plugged it back in, it started the first time with heat. I was plugged into a 30 amp system at the time.

In the troubleshooting guide I posted, on the page that talks about the control board, it says that to reset the board just turn the thermostat off and turn it back on again or pull the 12VDC fuse in the panel.

Letting it "sit for 30 minutes" sounds like air in the propane line to me.

Now the water heater has a rubber covered reset button.

[TURBS]

Sounds like air to me too!

[Superchief]

Last year when I had the issue, I tried starting it over a period of many days. I tired the turn on the stove trick, turn on the gas to the refrigerator trick, run the thermostat up and down trick, and every other trick that I could find, nothing worked. I tried this at least 50 times over that period. Not until I unplugged it and took it to the dealer did it work, and the first time they tried. I was glad, but beside myself. Okay this year, I had no problem starting it early in the season. Went on a 2 week trip south, never used it and when I came back north, there was a freeze warning where I live. Figured it was time to run the furnace for a couple of nights. As noted before it would not put out hot air, when the fan started. Went through the stove, refrigerator, and thermostat routine, still no heat. Only when I unplugged the Motor Home for 30 minutes and tried again, did I get heat. This has worked so far for me and thought it might be a quick fix for someone else. I can tell you it was frustrating last year when I tried it so many time over so many days without success, and then to have it start on the first try by the dealer staff.

[Herk7769]

Intermittent problems are always the hardest to troubleshoot.

You might want to do a "precautionary" replacement of the possible fail items; one at a time or all at once for the internal stuff.

It will be cheaper in the long run than paying a tech to troubleshoot it for a couple of hours at the shop bill rate, quote you the part at twice times its cost, then install it, again at the shop bill rate. You most likely could still save enough money to get a fancy new digital thermostat too.

Sail Switch
Propane solenoid
control board

Dinosaur Electronics Home. High quality circuit boards for RV appliances.

RV Furnaces, Heaters and Parts - PPL Motor Homes

[langeraf]

Many thanks for the inputs. I have a 2010 BH model. I have tried the routine that Superchief did with no luck. I am going to unplug for 30 min and then try it. Did you also close the battery cutoffs to shutdown the whole coach or just unplug?

[Superchief]

Just unplugged

[Herk7769]

<Sigh>, there is nothing 120 VAC in the furnace.
It is all 12VDC.

Unplugging without disconnecting the battery does nothing.
Just pull the 12VDC furnace fuse.

[Superchief]

I may have also turned off the disconnect switch, don't remember exactly. Doesn't hurt to do that also. Good luck !!!!

[Superchief]

Langeraf,

Just wondering how you made out with getting the furnace to heat?

[langeraf]

The 30 min reset did not work. Haven't had time to try anything else. Although I did just recently fill up with propane so I'm wondering if it is air in the line. The stove and fridge are working fine on propane.

thanks for the help.