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Old 09-22-2020, 12:46 PM   #1
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2016 rockwood roo 23ikss furnace problem

I am going to help my son diagnose and hopefully fix an issue with his furnace. It is a suburban furnace but I do not know the specific model number. Here is what I know so far. The fan operates on heat and the igniter clicks three times but does not light the furnace, the lines have been purged by running the stove etc, the propane tanks are full, you cannot access anything without cutting the wires and disconnecting the gas line and pulling the furnace based on what my son has described.

I plan to check for proper voltage, switch the propane tanks over, I donít think it is possible to check for spark, check the airflow sensor etc without pulling the furnace. Wondering if there are any other simple diagnostic checks I should be performing to identify the possible source of the problem ? Thanks.
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Old 09-23-2020, 07:13 AM   #2
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I would google the manual for the heater once you know what it is, I believe there are checks you can do without removing it and you should not have to cut wires to pull it out. I pulled mine out at one point in my ‘19 and it was tight but came out a ways still hooked up.

Clicking 3 times and shutting off means it went into a protection mode, probably because of the flame sensor not seeing anything, so things like no gas, dirty sensor, bad igniter, etc. would be my thoughts. Good luck!!!
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Old 09-23-2020, 07:44 AM   #3
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Found this, maybe it will help you...https://www.rvtravel.com/troubleshoo...nace-problems/

The one time this happened to me was in the middle of the night when my battery ran out of juice. I heard the clicks and the furnace would attempt to start but would not fire.. In the morning when I plugged it into the generator it fired right up. Simple to check, just plug into power and see if that resolves it.
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Old 09-23-2020, 07:46 AM   #4
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That RV most likely has a 35k btu furnace. And it's most likely the SF35F.
Here's the service manual for them. Suburban FURNACE Service and Training Manual
The troubleshooting guide starts on page 30.

Since it's clicking trying to fire that means that the sail switch is making and proving sufficient air flow. The clicking also means that the igniter is trying to spark.

It appears that the flame sense isn't seeing the flame, either because the furnace isn't lit or the flames sense isn't sensing the flame.
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Old 09-23-2020, 11:58 AM   #5
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One other thing to check. Make sure nothing is restricting the flow of air to the vents in the camper. A crushed vent duct, something in front of the vents etc.
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Old 09-23-2020, 02:29 PM   #6
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Check 12v Battery

Also ... check the 12v battery. I learned the hard way that even plugged into shore power, if the 12v battery isn't holding a charge, the furnace won't light. I'm not saying that this is THE problem, but I found out the hard way that it can be A problem.
I helped out a fellow camper in TN this summer that had the same issue... even when plugged into shore power, the dead battery caused all kinds of issues.
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Old 09-23-2020, 05:48 PM   #7
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Thanks

Appreciate all of the suggestions and feedback. I am visiting my son on Friday during his last camping trip of the season so will hopefully be able to fix....I will report back on what I find.
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Old 09-23-2020, 07:55 PM   #8
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A few other things

Quote:
Originally Posted by Bama Rambler View Post
That RV most likely has a 35k btu furnace. And it's most likely the SF35F.
Here's the service manual for them. Suburban FURNACE Service and Training Manual
The troubleshooting guide starts on page 30.

Since it's clicking trying to fire that means that the sail switch is making and proving sufficient air flow. The clicking also means that the igniter is trying to spark.

It appears that the flame sense isn't seeing the flame, either because the furnace isn't lit or the flames sense isn't sensing the flame.
Besides the vents and ducts in the camper, another potential spot to check are the intake and exhaust vents outside the camper. They are together outside, just opposite where the furnace is on the inside. They are one above the other on a chrome plate with two round grilles. Take a piece of wire and probe them. Maybe use a shop vac on both intake and blower mode on both vents. There is nothing you can damage this way.

2016 is pretty new. When trailers get to be 8-10 years old the propane regulator (by the tanks) starts to fail and regulation goes out of spec. The furnace is much more sensitive to this than the range or water heater. It really needs to be held to 11-14" water column (about 1/2 psi). I suppose it's possible that the regulator has gone bad.

Usually there is enough wire around that if you stuff loose wire into the side of the furnace plenum, you can pull the furnace guts out. If not, buy one of these.
  • Cut it in half.
  • Plug the two halves together. Pull the loop taut and cut all four wires, opposite from the plug. You will insert this assembly into the existing cable so it can be unplugged. Separate the two ends.
  • Determine which wire going to the furnace is ground.
  • Cut that wire only.
  • Find the connector that has one exposed contact and three covered contacts.
  • Connect the ground wire coming from the trailer to the wire going to the single exposed contact.
  • Connect the ground wire coming from the furnace to the corresponding (only insulated) contact on the other connector.
  • Now plug the two connectors together.
  • For each of the three remaining connectors, ONE AT A TIME,
  • Cut a wire.
  • Connect one cut end to one of the remaining connector wires
  • Connect the other cut end to the corresponding contact of the other connector.
Now you can simply unplug the furnace.
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Old 09-25-2020, 12:03 PM   #9
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Diagnosis

Here is what I know so far from checking the furnace

The battery is good 13.6 volts
The fan blows and then the igniter clicks three times but burner does not light
I took the access panel off both outside and for the furnace....they are clear
Took the igniter out and cleaned it....seems fine but with access panel off and looking into window in chamber you cannot see a spark when it clicks...Gap seems ok.
When the igniter is clicking, you can clearly smell propane from the exhaust outside....so gas is coming on...

Not sure where to go next....clearly no spark I think so check electrode and maybe the board....

Furnace model is an NT20sq..19000 btu

Any help would be appreciated. Thanks.
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Old 09-25-2020, 12:10 PM   #10
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I had similar going on with my 2016. I changed out the lp regulator and resolved my problem. It's a PIA to rig up a manometer. A regulator is about 50 bucks even from CW. Takes about 10 minutes to swap out
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Old 09-25-2020, 01:51 PM   #11
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Homemade manometer

Quote:
Originally Posted by jeff64 View Post
I had similar going on with my 2016. I changed out the lp regulator and resolved my problem. It's a PIA to rig up a manometer. A regulator is about 50 bucks even from CW. Takes about 10 minutes to swap out
This one took less than an hour to build and used less than $5 worth of fittings.
The tubing, the nylon barbed-to-pipe thread fitting, and the brass pipe-thread-to-flare fitting came from Lowe's. I had the wood straps and cable clamps on hand. This is set up so you can disconnect the flare fitting from the furnace and connect the manometer directly to it.

I cut the dado in the base to be a tight fit for the vertical board and just tapped the board in.

The lines on the vertical are 1/2" apart, but are numbered in inches, since the pressure pushes fluid on one side down which pushes the other side up.

There are a couple of drops of blue food dye in the water for easier viewing. Right now it's a little low.
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Old 09-26-2020, 07:09 AM   #12
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Igniter

In the trouble shooting guide it says if no spark replace the module.....why would not say replace the electrode......to me it is confusing......igniter or electrode is cheap so will try this first but cannot figure out how it could fail so soon with very little use and totally clean. Other question is module referring to a control board ??
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Old 09-26-2020, 07:33 AM   #13
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The electrode rarely if ever goes bad. It's almost always the module.

Yes that's the ignition control board they're referring to.
I suggest the Dinosaur replacement board if you need to replace the board.
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Old 09-26-2020, 09:17 AM   #14
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Just one thing...

Quote:
Originally Posted by Bama Rambler View Post
The electrode rarely if ever goes bad. It's almost always the module.

Yes that's the ignition control board they're referring to.
I suggest the Dinosaur replacement board if you need to replace the board.
Just one thing...it wouldn't hurt to go through the procedure for resetting the electrode gap first. It's in the manual.

If the gap is too wide, there will be no spark, or the spark will occur elsewhere, same as automotive ignition.

The sparking action could erode the tip of the electrode over time, enlarging the gap to the point that that there's no ignition.

EDIT: I should also have mentioned that it's been reported here that there were one or two years of bad production in which all all the boards failed. Your 2016 could fall in this range--you will see a burned spot on the back side of the board if that's the case. If so, call the manufacturer to see if they will send a free replacement.

EDIT 2: Now trying to remember whether the other EDIT applies to water heaters or furnaces. (SIGH)
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Old 10-10-2020, 07:03 AM   #15
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Update

Fast forward a few weeks for an uodate

My son replaced the igniter and still furnace will not light

A buddy helped him remove the furnace and he has a new igniter control board to install....I have a few questions.

Is the board a fairly easy job and is there a procedure outlined for removal and installation ?

The furnace vent cap was not removed and the furnace was just pulled....question, will it be possible to reinstall without the vent cap being removed. Process needed to do that ?

Anything else we should be aware of to do this job ?

Many thanks for all of the help thus far.......
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Old 10-10-2020, 07:48 AM   #16
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Good questions

Quote:
Originally Posted by macker View Post
Is the board a fairly easy job and is there a procedure outlined for removal and installation ?
It's straightforward. Just put the new board alongside the old one and transfer the wires or connectors one at a time. Don't pull everything off the old board at once.
Quote:
Originally Posted by macker View Post
The furnace vent cap was not removed and the furnace was just pulled....question, will it be possible to reinstall without the vent cap being removed. Process needed to do that ?
If you are patient and do some juggling, you can re-engage the furnace to the two tubes going to the outside port. It may take some time. If you have to remove the outside port, have some butyl tape on hand and use it. It's a very messy job, so do your best to avoid it.
Quote:
Originally Posted by macker View Post
Anything else we should be aware of to do this job ?
Be sure to get the gas flare fitting tight. After you have turned the gas back on, put a few drops of dishwashing liquid in a coffee cup and fill with water. Use a paintbrush to cover the fitting and watch for a few minutes to make sure no bubbles appear.
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Old 10-10-2020, 11:46 AM   #17
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It's always a good idea to take some pictures of the old board with everything hooked up. That way you can see how things were connected.
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Old 10-10-2020, 01:53 PM   #18
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I am very happy to report that the source of the problem was a faulty igniter board which was producing a weak spark........it has now been replaced and the spark is strong the burner lights up just fine now....so we really appreciate all of the helpful advice from forum members...We are very thankful indeed !!
The furnace was removed without taking the vent covers off and the wiring was not an issue to reconnect, overall went pretty smooth.
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Old 10-10-2020, 04:00 PM   #19
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That's good news. Thanks for coming back and letting us know that you got it fixed.
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