Suburban Furnace lighting issues

[Davelb]

Hello,

I have a 2003 Minnie 31c. I’ve owned it about a year and recently the suburban heater sf-35 went from intermittently working to now not working at all. When I turn it on at the thermostats,, after about 10 seconds the first ignition cycle attempt attempts to light it and does 3 cycles and never successfully lights the heater. The smell of gas is very strong from the exhaust vent leading up to each attempt for it to light itself, sail switch is working (otherwise I believe the gas would not be released) into the burner.

I took the front cover off on the inside of the rv for the heater box and it fires up every time. I read online to check to make sure the ducting is not obstructed if this is the case. It also states the burner box seals may be bad and pulling in to much air preventing it from lighting. I replaced the gaskets (they existing ones seemed in great condition, this rv was barely used by previous owner but I replaced anyway). It still only works with the front cover removed.

The only other thing I can think of is the igniter itself which I do hear clicking about 7 times for each attempt to light.

Anyone have any ideas on this?

[Morich]

Living in Central Texas, I've just got "reliable" power back and might try to throw some light?

sounds like you have done a good job so far and given much good info.
So to review, we think the sail switch is indicating proper air flow as you get gas smell. So step one and two are seeming to happen but it takes three things to light fuel at the right place, so you need to check that the connection is not totally loose and the gas not getting to the burner. That is probably just a good look at the pipe coming in and that it gets to the burner.
Two is that the sound you hear is actually the igniter and should sound somewhat like the piezo lighter on grills? And you might expect to see a spark as it clicks? So do a look at the igniter to make sure it is sparking and that the igniter is pretty close to the burner where the gas is expected? Not loose and fallen down and you might get a big pile of gas and sudden "swoosh/ boom " fire! Use some care to avoid losing the eyebrows!
Open outside door and let somebody turn the inside controls while you stand back at least a few feet!!
Gas and ignition but it also needs the proper amount of air to burn well, so there is often a thin sheet metal adjustment. Some look like a sleeve over the incoming gas pipe with a screw to let you loosen and slide around to adjust air. I would not first try to adjust unless it is obviously loose. Just no reason to add doubt if it appears to be firmly in place.

Something to be aware of is that there may be a thermocouple which should be in the flame and stay hot to keep the gas valve open and those may get burned off, etc. to stop working.
I have not done a full look at that model to know, so just a point to look over if you do see something like that.

Hope that gets you some ideas to look over and let us know what you find?

[imnprsd]

Just yesterday I came across this video on how to check for a bad Colman Mach Thermostat that controls a Suburban heater. I don't think this video will address your problem, but it is one to keep for future reference.

The tech discovered there was an intermittent Suburban start condition caused by an "unseated" pin in the connector as shown blow. And all he had to do is reseat the pin to get the Suburban heater working again!

Apparently, the blue wires out of the Suburban mate with the white & red wires at plug that go to the thermostat. His plug is located above the Suburban heater, and maybe you can access it from inside the RV? ...In my floor plan I have an access to the top of my heater under the sink.

https://www.youtube.com/watch?v=lJXT...DJyKF&index=15

[Morich]

Things have calmed a bit around here and I got most of the house put back in order (even got to take a shower!!!) and that let me get down to looking at this question a bit more.

I found that most of what I was going on is not exactly the same for your furnace as it is a bit different in some ways but the same in others.
One point I picked up is finding a troubleshooting section in a manual online!

Is this like the manual you might have found or different? It seems like it has a good section for trouble----but then I'm not trying to actually follow it, so that may not be as much help as it seems from reading!!

https://www.bdub.net/manuals/Suburba...ice_Manual.pdf

Down about page 27, may be some good info?