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Suburban Heater blowing cold air
Hello all! My 2000 Island Queen heater blows cold air when I’m plugged in, or on the generator. I have replaced all the parts in the heater, except the burner, as that seems to be fine. The heater works great on solar. It is only on power that the burner does not ignite. Have any of you come across this before? Any advice or ideas are appreciated 🙏
2000 30' Island Bed
Re: Heater blowing cold air
Reply #1 –
Quote from: LucytheTARDIS  - 
Hello all! My 2000 Island Queen heater blows cold air when I’m plugged in, or on the generator. I have replaced all the parts in the heater, except the burner, as that seems to be fine. The heater works great on solar. It is only on power that the burner does not ignite. Have any of you come across this before? Any advice or ideas are appreciated 🙏
Have you tested the thermostat?

Chris
Formerly: 2002 30' IB
Re: Heater blowing cold air
Reply #3 –
Quote from: LucytheTARDIS  - 
The heater works great on solar. It is only on power that the burner does not ignite.

If this is accurate, I would start there as a clue and suspect that maybe the batteries have low voltage.  Maybe your 12v converter isn't working properly, or is switched off at the breaker panel?

The typical heater startup process goes like this:
(1) Wall thermostat calls (send an electrical signal to the furnace) for heat. 
(2) Fan blows cold air.
(3) Sail switch closes, verifying that the fan is blowing
(4) High limit thermostat verifies that it's not too hot (overheating or on fire for some reason)
(5) Gas valve opens and burner ignites.  You can hear the change in sound once combustion starts.  You can also feel the heat in the coach as well as outside at the heater exhaust.

The heater will continue until the wall thermostat stops calling for heat, either the sail switch or the high limit thermostat indicate a problem, you run out of propane, or the battery voltage gets too low. 

People sometimes confuse step (2) for an operating furnace, when (5) is really where the magic happens.

Rich



2003 MB
Re: Suburban Heater blowing cold air
Reply #4 –
Thanks everyone!
Joan, I have already replaced the sail switch, and it works when I'm not plugged in.
Chris, the thermostat works when I'm not plugged in, so I can't imagine that would be the problem.
Rich, maybe I don't understand how things work, but wouldn't weak batteries only be the problem when I'm not plugged in?
The first 4 steps happen perfectly. The fifth step, the click happens, and sometimes the burner ignites, but only for a moment, then immediately goes out again. It continues to try for a while, but eventually just cycles through blowing only cold air.
2000 30' Island Bed
Re: Suburban Heater blowing cold air
Reply #5 –
Lucy, that sounds like either an ignition problem or a propane problem.  In Rich's step 5, if the ignition process is begun and a sensor does not detect ignition within a few seconds, the propane supply is shut off.  Failure to ignite could be due to a bad board providing insufficient voltage to the ignitor, an ignitor that is gapped improperly, that is damaged or shorted, or improper propane and air flow either from a solenoid issue, an aperture jet issue, a spider nest in the propane path, or something else along those lines.

I will illustrate with my own tale of woe, for my water heater rather than the furnace.  I had serviced my heater, and after, the heater refused to light.  Everything looked right and sounded right, but the heater would make its three tries, then shut down.  I eventually found the issue.  The ignitor is surrounded by a ceramic insulator.  Mine had gotten wet and, even after drying its surface, it was not producing sufficient spark to light the propane jet.  After 24 hours of drying, everything went back to normal and my heater worked just fine. 

The point of the illustration is that something small in the ignition process can prevent ignition.  You have covered the basics with steps 1 to 4.  At this point, I think you should find a place to provide professional service of your heater.

Ken F in NM
'08 MB
Re: Suburban Heater blowing cold air
Reply #6 –
Quote from: LucytheTARDIS  - 
Thanks everyone!
Joan, I have already replaced the sail switch, and it works when I'm not plugged in.
Chris, the thermostat works when I'm not plugged in, so I can't imagine that would be the problem.
Rich, maybe I don't understand how things work, but wouldn't weak batteries only be the problem when I'm not plugged in?
The first 4 steps happen perfectly. The fifth step, the click happens, and sometimes the burner ignites, but only for a moment, then immediately goes out again. It continues to try for a while, but eventually just cycles through blowing only cold air.
Lucy, (is that your name?), I went through the same process/analysis you have and it turned out to be the thermostat even though I could short circuit the thermostat with a paper clip and make it come on. And since the furnace/thermostat works off either battery or 120v, whether you are plugged in or not shouldn't make a difference. I would suggest you invest $25 in a new digital thermostat, hook it up and see if that is your problem. If not, the worse thing that happens is you have a spare thermostat and I am wrong.

Chris
Formerly: 2002 30' IB
Re: Suburban Heater blowing cold air
Reply #7 –
Quote from: LucytheTARDIS  - 
Rich, maybe I don't understand how things work, but wouldn't weak batteries only be the problem when I'm not plugged in?
The first 4 steps happen perfectly. The fifth step, the click happens, and sometimes the burner ignites, but only for a moment, then immediately goes out again. It continues to try for a while, but eventually just cycles through blowing only cold air.

My first sentence has a few caveats for good reason.  Weak batteries would only be a problem when plugged in if the 12v converter isn't working, and you're not in the sun.  In other words, weak batteries can be hidden by either solar charging or a working 12V converter while plugged in.

It could be that working on solar is a coincidence and not a cause.

If you're making it to step 4, Kenneth is right on track.  I left a few things out in step 5 that he correctly points out.  I should have written something like (5) Gas valve opens and ignitor clicks to create sparks and ignite the burner.  No spark = no heat.  If there is no heat, the thermocouple next to the ignitor will not sense a flame and shut off propane flow for safety.

 Ignitor problems can be intermittent and frustrating.  If the ceramic on the ignitor cracks (with age), they can sometimes let in moisture and prevent ignition.  On a dry day (when the sun is out --> solar), things can dry out and it will work fine.

Lighting for a few second and then going out is a sign that the thermocouple isn't sensing a flame for some reason.  For safety reasons, the heater is designed to shut off the propane when it's not burning. 

If you're comfortable with it, I would start by double checking the battery voltage (while the fan is running) and then shorting the thermostat (paperclip or touching the call wires together) to eliminate those two possible problems.  Then, if you still get to step 4, focus on the propane valve and ignitor area.  Determine if it's not lighting (ignitor or valve) or lighting and then turning off (thermocouple).

Rich

2003 MB
Re: Suburban Heater blowing cold air
Reply #8 –
Thank you all, I really appreciate all the information. I definitely have a lot to check out this weekend. Kenneth, I have taken this to several professionals. They all tell me it’s fixed, but the problem comes back up every time. This is why I reached out here. Chris, Lucy is my RV. My name is actually Amory, thank you for asking. Sounds like the thermostat would be worth a try! Rich, I appreciate the clarification. You guys are amazing! I’ll let you know what I discover.
2000 30' Island Bed
Re: Suburban Heater blowing cold air
Reply #9 –
Difference in voltage getting to the igniter perhaps? I would think it is using the same wiring and fuses either way.
Maybe the igniter is weak and solar putting out a higher voltage?
Steve and Jill, Steve posting
1999 26.5 Mid-Bath
Re: Suburban Heater blowing cold air
Reply #10 –
Hi Amory. I get the Tardis reference and it is a very good name!   So your 2000 coach propane space heater works with solar boosting your house 12 volts, probably about 13.8 volts with sunlight.  But doesn't work with shore power AC or generator AC. Both of those go through your old outdated Parallax 6345 converter/12v supply and battery charger.   I just replaced my 12v supply with a Progressive Dynamics 4655VL, and a new design fuse panel. The old converter, I thought it had an excessive amount of 'ripple' on the 12v. house circuit. (probably an ageing capacitor)  Your coach might have an RV-30S solar controller, with no digital readout of the voltage, or was your solar added  or upgraded before you got the coach?  Such poor quality 12 volts, really about 13.5 volts from the converter might affect the heater control circuitry.
    Does your space heater work at night without shore power?  A digital meter would tell me the battery voltage without solar assist.  12.6 volts or higher would be good.  The problem might not be in the heater itself as Rich stated. It might be the voltage supplied by the converter, or a problem with the batteries.     RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Suburban Heater blowing cold air
Reply #11 –
Amory, there are pros (people who charge money to work on your stuff) and there are pros (people who really know what they are doing).  Often they are not the same.  You want the second type.  If a "pro" tells you it is fine, and it doesn't work right, you have two options.  You can give the "pro" a second chance to fix it, with credit for your first visit because it was not fixed, or you can find someone else.  The way I found my current appliance service guy is I emailed either Dometic or Suburban, and asked for the name of a certified service person in my area.  I have been with the person they sent me to ever since, and have never had a word of dissatisfaction regarding his work.

Ken F in NM
'08 MB
Re: Suburban Heater blowing cold air
Reply #12 –
Thanks Ron! Nice to know there’s another whovian!
The heater does work at night without shore power. I’m definitely thinking it’s a problem with the power converter. I will install it this weekend, and hope it fixes the problem 🤞
2000 30' Island Bed
Re: Suburban Heater blowing cold air
Reply #13 –
Amory, there is another thing around step 5 from above. When the flame ignites there is a flame sensor that has to prove flame with in 3 seconds or so. If it doesn't prove it will retry till it locks out and then you will have cold air blowing. If it were mine I would remove the flame sensor and clean it with fine sand paper and then run it through it's paces again. They are notorious for getting dirty and not sensing the flame. They have to have a very good ground. Propane furnaces are not to be taken lightly and if you aren't comfortable with it, by all means hire someone.

Jon
1994 MB
Re: Suburban Heater blowing cold air
Reply #14 –
Okay, so just for the record, I have had professional help every step of the way, so please feel free to stop suggesting I hire a professional. We replaced the power converter, which was probably a good idea anyway, but did not fix the problem. We replaced the thermostat, which did seem to improve my heater overall, but still did not fix the problem. This is very frustrating. We have tested the voltage in every situation, and that does not seem to be an issue. It still only fails on shore power or generator.
2000 30' Island Bed
Re: Suburban Heater blowing cold air
Reply #15 –
Amory, since the furnace works at night when solar is inactive, that would rule out the batteries as a problem. This means there is no logical way anyone can think of that using shorepower or generator alone should disable the furnace. Are you the original owner? If not, is there a possibility the previous owner had a modification made, such as an AC powered propane cutoff valve, perhaps to prevent the furnace from using up propane while on shorepower? Seems extreme, but the furnace IS pretty inefficient, so most folks use electric heaters and such with shorepower...

Steve
2004 FL
2013 Honda Fit
Re: Suburban Heater blowing cold air
Reply #16 –
Lucy,
Is there a difference in where you run the furnace on shore power vs without shore power.  Such as no shore power being at a high elevation (that can affect things) and shore power being at a low elevation.
Jane
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
 
Re: Suburban Heater blowing cold air
Reply #17 –
I think we’ve finally solved it! There are 3 rubber gaskets around the holes of the metal frame the thermocouple runs through. One of them had slipped (or just wasn’t installed properly 🤷‍♀️). On battery power, there wasn’t enough energy to cause a problem. On shore power, the additional voltage was causing it to arc in that spot, making it sound like the proper series of events, but it was not actually igniting the burner. I hope this information helps save someone else time, money, and headache in the future!
2000 30' Island Bed
Re: Suburban Heater blowing cold air
Reply #18 –
Amory, thanks a bunch for following up with the "fix". Many folks forget to do that. Plus, we have a great Suburban heater troubleshooting thread for future reference. Did you figure this out yourselves or from a mechanic?

Chris
Formerly: 2002 30' IB
Re: Suburban Heater blowing cold air
Reply #19 –
Quote from: LucytheTARDIS  - 
I think we’ve finally solved it! There are 3 rubber gaskets around the holes of the metal frame the thermocouple runs through. One of them had slipped (or just wasn’t installed properly 🤷‍♀️). On battery power, there wasn’t enough energy to cause a problem. On shore power, the additional voltage was causing it to arc in that spot, making it sound like the proper series of events, but it was not actually igniting the burner. I hope this information helps save someone else time, money, and headache in the future!

I'm guessing it is the igniter wire - not the thermocouple? A thermocouple would not have more than a few millivolts, and would not arc.

Steve
2004 FL
2013 Honda Fit
Re: Suburban Heater blowing cold air
Reply #20 –
There are 3 rubber gaskets around the holes of the metal frame the thermocouple runs through. One of them had slipped (or just wasn't installed properly.

I don't have a clue what you are talking about, Amory. Picture?
Don & Dorothy
Sold our LD in June of 2023

Our boring always non-PC travel blog
Traveling Dorothy
Re: Suburban Heater blowing cold air
Reply #21 –
Steve, yes, the igniter wire! Sorry.
2000 30' Island Bed
Re: Suburban Heater blowing cold air
Reply #22 –
Don, I don’t have a picture, and I’m not pulling it back apart.
2000 30' Island Bed
Re: Suburban Heater blowing cold air
Reply #23 –
Chris, thanks for letting me know!
My step-dad and I figured it out. I got sick of paying mechanics to not fix it.
2000 30' Island Bed