Attempting to fix propane furnace.

[joem789]

Hi there.

This is my first post on the forums.

Our TT is a 2003 KZ SPORTSMEN 32'. It has a propane furnace underneath the norcold fridge. Its all the way back against the back wall. A metal box. I am fairly saavy with doing repairs on most things. But i like to do my homework first.

Our furnace has worked fine and over the last year the heat output hasnt been as strong. But it worked. Suddenly the other day it didnt kick on. So i turned it off and back on to cause it to kick on. I waited a few seconds for the loud click (when it lights). It clicked. A couple seconds later i heard the dreaded second click you hear when its outta propane. But we have propane. Stove works fine. Although the stove flames are all blue. But strong.

So i am not certain on where to begin. Id like to know what causes the furnace to act as if there is no propane supply. Thanks.

[WinnieView]

Is the fridge running on propane? What about if you turn off all other propane devices and just try the furnace?

[steve52]

When your furnace starts, the fan comes on. If there is sufficient air flow, it will then try to ignite. If it doesn't ignite, it stops.

You are hearing the click, so it is trying to light.

Furnace needs 12v DC. Are you plugged in to shore power? Is your battery charged?

What brand/model is the furnace?

[twinboat]

A stove doesn't use near as much propane as a furnace.

Confirm enough propane in the tank.

[777 Driver]

If you can provide manufacturer and model of the furnace, it's easier for others to offer specific assistance. One other common problem is a fault in the flame sensor. The logic most furnaces use calls first for a blower to start followed by a commsnd for the burner to ignite. Shortly after the burner light command, a flame sensor checks to make sure that the burner did ignite. IF the flame sensor doesn't sense a flame, it will command the gas valve in the furnace to close. You don't want gas flowing unless the burner is lit. Sometimes, even though the burner does light, the flame sensor malfunctions and turns off the gas. Often, it only takes cleaning or repositioning the flame sensor to get it working properly.

Do be careful, though, because there is real fire or carbon monoxide hazard from a malfunctioning furnace.

Welcome to the forum.

Take care,
Stu

[grindstone01]

I had the same furnace issue including the second click symptom a couple of years ago and it turned out to be the igniter gap was too large (the igniter tip probably eroded with use). I bent the tip of the igniter and it worked good. I had to remove the furnace to get to the igniter which only involved a couple of screws and the gas line.

[Old-Biscuit]

Thermostat closes....CLICK
Furnace Fan comes on....runs 30-90 seconds to purge combustion chamber and get up to full speed/air flow
Sail switch closes and DC goes to circuit board
Circuit Board then energizes the gas valve and Spark electrode
Ignitor lights off main flame
Main Flame generates a 'flame signal' which is used to PROVE flame is lit


No main flame/no signal....circuit board shuts down DC to gas valve so raw unlit fuel doesn't accumulate


Could be low airflow (sail switch not closing/sticky)
Could be low DC Voltage

Could be dirty/loose connections
Could be bad ground circuit
Could be spark electrode...soot/carbon/gap/bad high voltage wire/cracked ceramic insulator
Could be spider webs....yes spider webs. They can interfere with the fuel/air mixing properly (propane pressure is on 0.4 psi)


Could be circuit board


First is a good cleaning---burner slots, spark electrode, connectors
Spark gap---1/8" to 3/16"

Second is use a voltmeter and trace the DC circuit (gas valve only has DC applied for 6-8 seconds during trial for ignition)




Brand /Model for wiring diagram

[Pepper2]

I have never worked in the confined area of a RV furnace so what I suggest may be difficult.
Make sure your fan is clean. If not, you will not have enough air flow to trip the sail switch.
Check the continuity of the sail switch. No continuity, then the switch is bad.
In the furnace's I've worked on you could bend the sail on the sail switch slightly so it grabbed more air flow in order for the furnace to light. If this works, replace with a new sail switch.

[KM Rolling]

Originally Posted by Old-Biscuit

Thermostat closes....CLICK
Furnace Fan comes on....runs 30-90 seconds to purge combustion chamber and get up to full speed/air flow
Sail switch closes and DC goes to circuit board
Circuit Board then energizes the gas valve and Spark electrode
Ignitor lights off main flame
Main Flame generates a 'flame signal' which is used to PROVE flame is lit


No main flame/no signal....circuit board shuts down DC to gas valve so raw unlit fuel doesn't accumulate


Could be low airflow (sail switch not closing/sticky)
Could be low DC Voltage

Could be dirty/loose connections
Could be bad ground circuit
Could be spark electrode...soot/carbon/gap/bad high voltage wire/cracked ceramic insulator
Could be spider webs....yes spider webs. They can interfere with the fuel/air mixing properly (propane pressure is on 0.4 psi)


Could be circuit board


First is a good cleaning---burner slots, spark electrode, connectors
Spark gap---1/8" to 3/16"

Second is use a voltmeter and trace the DC circuit (gas valve only has DC applied for 6-8 seconds during trial for ignition)




Brand /Model for wiring diagram

Good info above!

I had a similar problem as the OP. After eliminating almost all other possibilities, concluded it was the circuit board. Replaced it with a dino board and all has been functioning great since then.

[EodCmdr]

Woke up this morning to same problem. $130 later, RV tech hit reset switch on furnace and all is good. At least I know where the reset is now.

[joem789]

Thanks for all the advice.

I don't know the brand or model. Will have to dig out the papers for the camper. We're plugged into shore power. And the furnace has never been cleaned. It acts the way it does when propane runs out. Starts when it should. Tries to light when it should. But clicks off like propane is empty.

By what's been posted i reckon I'm gonna have to just try and disconnect and pull out the box to check things out. I'd love to leave it alone and rely on supplemental heating. But we're winter camping and the furnace helps keep things thawed while we're away.

I'll pick a day when i can tackle this and report back here. Thanks a lot!

[AbdRahim]

Where is the reset switch?

[bmchoug]

Originally Posted by joem789

Thanks for all the advice.

I don't know the brand or model. Will have to dig out the papers for the camper. We're plugged into shore power. And the furnace has never been cleaned. It acts the way it does when propane runs out. Starts when it should. Tries to light when it should. But clicks off like propane is empty.

By what's been posted i reckon I'm gonna have to just try and disconnect and pull out the box to check things out. I'd love to leave it alone and rely on supplemental heating. But we're winter camping and the furnace helps keep things thawed while we're away.

I'll pick a day when i can tackle this and report back here. Thanks a lot!

Try Shutting off your propane tanks and disconnecting them. Wait 30 seconds and re connect. then very, very slowly open the gas valves. If you open the tanks too quickly, it will activate the excess flow valves. This will allow just enough propane through to light the stove but not the furnace.

[joem789]

Hi again

Well. When i removed the grill i realized its been a few years since I cleaned under the fridge. The furnace box was covered in dirt. I got it all cleaned up. Took the front panel off the box to get a look inside, which basically was clean. I fired up the furnace with the panel off. Effectively bypassing the floor vents. Air blew oit the box. Heater worked fine. Warmed up. So i would assume it was either a semi blocked return air, or floor vents.

So the furnace worked all day and early this morning afyer i kicked on, i heard a rumble. Then it acted the way ot did before. Wont stay lit. I forgot to mention yhe same rumble happened the first time it stopped heating. Couldthis just be a regulator issue? I did mention the stove burners are blue. And sometimes the oven burner will struggle. Does a bad regulator slow the gas flow?