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Old 01-10-2020, 12:53 PM   #1
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No furnace heat - 2003 35' adventurer

My 2003 35' adventurer furnace heater doesn't work. The fan doesn't come on, it does work in the "on" position. I was messing around with the thermostat and managed to mess up the contacts so the thermostat was replaced with original type. The batteries are fully charged, full tank of propane. Tried looking at the furnace and it is pretty well buried. I don't see a breaker for the furnace, but all of the chassis look to be OK. I was looking at this print for the heating/cooling and it is a little confusing
http://www.winnebagoind.com/diagram/...ire_138913.pdf
It's not real clear what turned the fan on...
Any thoughts?
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Old 01-10-2020, 01:05 PM   #2
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Hi, can you please explain what "The fan doesn't come on, it does work in the "on" position" means exactly? You say it doesn't and then does work. So, I know I for one am confused about the actual issue.
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Old 01-10-2020, 03:35 PM   #3
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Who is the manufacturer of your furnace and what is the model number? Did this furnace use to work and then stopped? Mine has a 15amp fuse but no breaker, however I don't think the fan would come on at all if the fuse was blown. Do your other lp gas appliances work okay?
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Old 01-11-2020, 10:04 AM   #4
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The fan mode switch can be in the auto position, for auto heat or cool or the On position, where the fans runs continuously. Works in the on position, not in the auto. Fan is supposed to come on for a bit, making a fan switch before the furnace lights
Yes, the stove lights and the fridge can be run on propane. It worked before and just stopped. Not sure who the make of the furnace is...
I was hoping someone knew of a breaker or fuse or quick fix for this.
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Old 01-13-2020, 01:09 PM   #5
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It is a Suburban model SF-42.
Yes it just stopped working.
I an hear a relay or something click outside, I think. I am going to look at the unit itself. Found the manual for it and I need the thermostat switch and a valve switch[NC] to be closed to get to the motor PCB . I am guessing that I have a problem on the motor board...
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Old 01-13-2020, 03:55 PM   #6
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Two clicks might be heard. One is the contacts in the thermostat itself if that type, while there is often a second click heard when the gas valve opens, so do some listening to be sure which you are hearing. But from there, there are several small points before saying the board is bad.
1. The thermostat has to close and call for heat
2. The blower has to start and get air moving. this air movement has to move a "sail switch" which is kind of a flap in the airflow. When the flap moves, it closes a contact for the rest of the operation. So a simple thing like a wasp nest in the airflow can stop the air moving and kill the operation! Common to happen if there is not a screen/guard over the outside heater vents.
Once air is flowing, there is a small delay and then the gas valve opens and then the lighting should start. Several things can go wrong there but worthwhile to start and get to that point first. If the gas valve is opening, it is okay to skip ahead to this point. One way to tell if it is the valve opening is to feel for vibration while somebody turns the heat on. You can often feel it. Valve opens and no lighting, then look at gas flow and the lighting process?
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Old 01-14-2020, 11:05 AM   #7
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Right, there is 2 clicks-thermostat and outside.
The sail switch circuit is a latching circuit after the fan starts, I never get the fan to come on, so this is never made. As I said, the fan comes on in fan mode "on" position.. The print I have says I need the thermostat and the valve switch closed to get the fan first started-must be through relay contacts on the motor board. The is no print for the motor PCB
I will check the valve switch. It just looks like a real pain to get to...
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Old 01-14-2020, 12:25 PM   #8
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Originally Posted by CoorsPowered View Post
Right, there is 2 clicks-thermostat and outside.
The sail switch circuit is a latching circuit after the fan starts, I never get the fan to come on, so this is never made. As I said, the fan comes on in fan mode "on" position.. The print I have says I need the thermostat and the valve switch closed to get the fan first started-must be through relay contacts on the motor board. The is no print for the motor PCB
I will check the valve switch. It just looks like a real pain to get to...
Shooting in the dark, but I might want to verify the contacts/wiring are good on the thermostat. Not sure that having the fan run when clicked to full time assures the contact for it to start fan on regular cycle????
You are getting two clicks? One for the small click at the thermostat and then one at the gas valve as it opens? Thinking this is not correct as the gas valve should not open until the sail switch verifies enough airflow.
I'm fully open to the idea that I'm not reading what you are saying, though!!
I think of the thermostat as the switch which first turns on the fan almost immediately, then IF that happens, the sail switch starts a time cycle and after a bit the gas valve opens with a click.
So that leaves me wondering about the second click being the gas valve or if it is another click that you are hearing and not the gas valve. The gas valve should not open as it is a safety to avoid filling things with gas if there is not enough airflow.
Sorry, more questions than answers!
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Old 01-14-2020, 02:30 PM   #9
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Coors Powered, your problem is an interesting one. From the drawings, I don't see how the fan (blower) runs with the thermostat set to heat, the fan set to on, but the temperature set on the thermostat not to demand heat. I think you would need four wires to the furnace: +12V, GND, heat, and fan to control heat and fan separately...but I only see three wires on the drawing. Of course, there are a lot of options that may not be in the drawings I looked at. Regarding the sail switch, on some units before the fan will come on, the sail switch must be open. Then, once the fan kicks in, the sail switch will close and that enables the burner to light. Maybe the sail switch is stuck closed? I have seen other reports of problems with sail switches.
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Old 01-15-2020, 07:44 PM   #10
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CoorsPowered, The FAN MODE and FAN SPEED only control the AC/Heat pump unit. 12V DC to power the furnace comes from the HOUSE 12V CIRCUIT BREAKER PANEL and the call for heat signal comes from the thermostat when the GAS HEAT is selected and room temperature is below set point.
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Old 01-16-2020, 09:20 AM   #11
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We need to make sure we are all speaking the same on forums as it is so easy to get bad info going!
We are speaking of a standard gas fired furnace I believe, not a heat pump as they are very much different.
At this point, I would have to have some more info from the OP to check what he is actually finding. If I am reading correctly and he is getting a second click from the gas vale opening while there is no fan running, it's time to be very carefull because there is something very wrong!
The reason for the sail switch is to make sure the gas valve can't open until the sail switch verifies there is enough airflow to carry any fumes or gas out of the RV. If the gas valve opens before the sail switch operates, there is potential for the RV to be filled with propane gas. NOT something we want to happen!
So I have to know what is really happening and I will have to assume the OP will get back to us when he has time or info to share.
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Old 01-16-2020, 12:49 PM   #12
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Thanks for all your help. I have answered a lot of your questions in previous entries.
I found there is a trouble shooting guide for the suburban gas furnace model sf-42 that I am going to use when the weather improves.
Was hoping not to mess with the furnace since it looks to be a real pain to get to, but it looks like it is coming to that.
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Old 01-16-2020, 01:00 PM   #13
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Good deal on the troubleshooting guide as they are often the most reliable--but do have some faults to be aware of at times.
Generally they are good but there are some which tend to get too generic and may not always follow what your specific item has and then a second faut I have found is that they can sometimes lead one into changning parts when not needed.
They can be good but do avoid changing parts too quickly. One case of this is when they lead to testing and give you the idea that because power is leaving point "A" it necessarily gets to point "B". They sometimes fail to mention small points like taking the connections loose from things like screws and looking for loose or corroded connections.
I find it worth the time to just take some of the small wires loose one at a time and make sure they are clean and making good contact!
Good luck on the chase!
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Old 01-16-2020, 02:21 PM   #14
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Suburban

That entire furnace is the size of a standard suitcase and can be easily removed. More than likely either wasps or circuit board.
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Old 01-17-2020, 09:33 PM   #15
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Start with the simple first which is to blow out the units combustion chanber exhaust and intake ports with a shop vac. However if the thermostat switches the furnace fan on manually and not automatically you really need to verify the operation of the thermostat when it calls for heat before going any further.

First thing is to ensure that it is indeed in heat mode and it is the gas furnaces 12 volt fan and not the Basement Airs 110 volt Air Conditioning fan. The air handlers fan comes on first and you may hear a damper clank when switching from Air Conditioning to heat. Once airflow is established then the burner will go through its ignition sequence.

I have basically the same system and there are no 110 volt breakers for the gas heat just the 12 volt popups over the microwave and potentially behind the false panel behind the top riser in the stair well.
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Old 01-21-2020, 12:12 PM   #16
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Found the problem.
On the furnace PCB,The relay for the motor [K2] was actuating , but the relay output pin, that goes to the motor wire, had come unsoldered, so it wasn't making a good connection. Pulled the PCB and soldered the pin and furnace works fine.
Thanks for everyone's help and inputs.
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Old 01-21-2020, 06:04 PM   #17
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Quote:
Originally Posted by CoorsPowered View Post
Found the problem.
On the furnace PCB,The relay for the motor [K2] was actuating , but the relay output pin, that goes to the motor wire, had come unsoldered, so it wasn't making a good connection. Pulled the PCB and soldered the pin and furnace works fine.
Thanks for everyone's help and inputs.
Congrats on two points! One on finding and fixing the problem as that gets double bonus! But then also I want to pass on congrats for reporting back what trouble you found.
And you can certainly pat yourself on the back for saving money as it is almost certain an RV tech would have simply gone for a new board.
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