Community Forums

weissb · 01-25-2025, 01:59 PM

Hi there,

My furnace's electrode will not produce a spark. Initial indication of the issue was: upon turning on the thermostat, the furnace powers up the fan, furnace releases propane, furnace attempts to ignite the propane with the electrode, and fails. It goes through 3 attempts then goes into ignition lockout. It is in a '96 Elkhorn truck camper, furnace is an Atwood 7920-ii Hydroflame.

I took the furnace out and gave it a thorough cleaning - had dust bunnies all around sail switch and a few dead bugs in the burner head/around the propane orifice.

Tried again after cleaning and still had the same issue. Determined issue was likely the electrode and went from there. While purchasing a new electrode I also purchased and changed the sail switch and high-limit temp switch; still no fix.

At this point I noticed the circuit board was not giving the proper 3-blink error code after going into lockout. It would also make a strange ticking sound during the period where the high-voltage line to the electrode would be receiving power. I replaced the circuit board with a new one, and now the ticking sound is gone and the board displays the proper 3-blink error code after "ignition lockout mode".

Through testing with a multimeter, there is 12V everywhere it should be/when it should be there (relay, high-limit switch, circuit board connections, propane solenoids).

I have read every post I could find on several forums and talked to a couple RV techs on the phone, and everyone suggests that this issue is either circuit board or electrode, which I have replaced both of.

My only guess at this point is that the circuit board arrived DOA. My assumption now is that the issue was always the circuit board, and the new one is defective also (I bought a $50 cheapy board). I have now ordered a Dinosaur Board and sent up a couple prayers.

No heat in the winter in Canada is less than ideal! Any help would be appreciated.

terrylane · 01-25-2025, 02:15 PM

"I am having issues getting my furnace's electrode to spark. Initial symptom was the furnace powering up the fan, attempting to ignite, and failing."

Hard to understand what you are saying.
Can you report the exact steps that you are seeing.
"Issues" and "failing" are not useful descriptors for troubleshooting.

weissb · 01-25-2025, 02:27 PM

Quote:

Originally Posted by terrylane

"I am having issues getting my furnace's electrode to spark. Initial symptom was the furnace powering up the fan, attempting to ignite, and failing."

Hard to understand what you are saying.
Can you report the exact steps that you are seeing.
"Issues" and "failing" are not useful descriptors for troubleshooting.

Current process of the furnace after all troubleshooting so far:
-Turn on thermostat, fan receives power, fan starts to run.
-After the fan runs for about 20 seconds I can hear and smell the propane valves opening.
-DO NOT hear or see the electrode sparking.
-Furnace goes through 3 cycles of releasing propane then attempting to spark electrode.
-After 3 attempts, it goes into "ignition lockout mode" with a 3-blink error code.

Old-Biscuit · 01-25-2025, 02:49 PM

When circuit board gets DC thru the sail/limit switch circuit it sends DC to gas valve AND Spark Electrode

If gas valve is being energized then the transformer on circuit board should also be energized.....high voltage DC from it thru high tension wire to electrode
(new electrode should fire IF transformer on circuit board was being energized)
*Suspect reach for 'cheap' board

Dinosaur Board is high quality........and their tech support is happy to help

Post back if Dino Board doesn't cure your lack of spark issue

weissb · 01-25-2025, 03:01 PM

Quote:

Originally Posted by Old-Biscuit

When circuit board gets DC thru the sail/limit switch circuit it sends DC to gas valve AND Spark Electrode

If gas valve is being energized then the transformer on circuit board should also be energized.....high voltage DC from it thru high tension wire to electrode
(new electrode should fire IF transformer on circuit board was being energized)
*Suspect reach for 'cheap' board

Dinosaur Board is high quality........and their tech support is happy to help

Post back if Dino Board doesn't cure your lack of spark issue

Thanks for the info, I appreciate it. So if the propane valve is being energized, which I can hear and smell and read on my multimeter, the issue is very likely to be with the high voltage line not receiving high voltage DC?

When I test the resistance on the coils on the propane valve, they read about 20ohms. From what I've read online, 20 ohms is normal for a propane valve. The Atwood troubleshooting manual I found said they should be 30 ohms. Not sure if this is possible with what's on the board, but could the circuit board be reading the amount of resistance through the coils, and restricting power to the high voltage DC line if the resistance is low? I can smell propane strongly, so I don't really think this has anything to do with it, but it's at the limits of my electrical understanding.

terrylane · 01-25-2025, 05:25 PM

Did you replace the electrical cord that goes from the igniter to the sparker assembly?

If so, the other thing to check is that it is sparking across the path of the pilot gas.

If it is sparking as expected, the next thing to check is that the orifice inside the pilot assembly is not plugged and blocking the flow of gas.

Be careful, propane is heavier than air and may accumulate in low spots or other unexpected places.

Old-Biscuit · 01-25-2025, 07:49 PM

Quote:

Originally Posted by weissb

Thanks for the info, I appreciate it. So if the propane valve is being energized, which I can hear and smell and read on my multimeter, the issue is very likely to be with the high voltage line not receiving high voltage DC?

When I test the resistance on the coils on the propane valve, they read about 20ohms. From what I've read online, 20 ohms is normal for a propane valve. The Atwood troubleshooting manual I found said they should be 30 ohms. Not sure if this is possible with what's on the board, but could the circuit board be reading the amount of resistance through the coils, and restricting power to the high voltage DC line if the resistance is low? I can smell propane strongly, so I don't really think this has anything to do with it, but it's at the limits of my electrical understanding.

If testing the gas valve solenoids in parallel then should be 15-25ohms
If testing them isolated (one at a time) then should be 30-50 ohms

Circuit board does not sense resistance of gas valve solenoids
DC is sent at same time to gas valve & spark electrode when trial for ignition is called for

DFord · 01-25-2025, 10:27 PM

I had igniter problems last year. When I gently pulled on the wire from the control board to the ignitor, it came right out! I had broken inside the electrode and wasn't noticeable. The only fix was to replace the ignitor electrode.

scamperscoo · 01-31-2025, 11:44 AM

Hey guys I've been reading this discussion with interest. I am troubleshooting an Atwood 7920-ii furnace that will not light.

I have a question regarding the 12 volts that is supplied to the circuit board via the sail switch. Does that voltage come directly from the 12v battery?

If so that may be my issue. For all I know, the battery on this camper is stone dead. It has been sitting unused for a couple of years. I thought the battery was completely out of the loop if the camper was plugged into shore power. But now I'm realizing I may be wrong about that?

scamperscoo · 01-31-2025, 02:20 PM

<edit> I went back to where this trailer is. Sure enough the battery is completely dead. So I hooked up a fresh battery and tried again.

This time I measured and I have 12 volts on the white wire on the circuit board connector. It still does not fire, but this time I did hear the sound of the igniter buzzing a couple of times for a second or two. So I suspect that the transformer or something else on the board has failed. I am now eyeballing one of those $40 boards on Amazon..

DFord · 01-31-2025, 08:21 PM

Flame Rectification & How a Flame Rod Knows What it Knows
https://wardburner.com/flame-rod-works/

The control board creates an A/C signal from the 12v D/C available on the RV. That signal is applied to the flame rod causing it to spark. As soon as the flame ignites, it passes a very small D/C current (micro amps) back to the control board and the sparking stops - the flame is proven at this point. The control board must have a good ground to receive that signal. If anything were to short out the flame rod (a flake of rust?), the control board would see the A/C signal coming back and shut everything down. If the flame isn't proven in a second or two, the control board stops the sparking and shuts everything down. It will allow that process to repeat 3 times before it locks out and stops trying. Cycling power at the water heater switch will restart the attempts to prove a flame.