Help w/heater
- Thread starter FredX
- Start date
dwh
Tail-End Charlie
My camper has an NT-12SE. Does yours do anything at all? I.e., does the fan even spin up?
On mine, the fan spools up to speed and then the gas valve opens and the ignitor does the tickticktick thing.
Dinosaur makes replacement control boards that also add fan control. They can usually be found for around 100 bucks:
http://www.dinosaurelectronics.com/Ignitor_boards.htm
On mine, the fan spools up to speed and then the gas valve opens and the ignitor does the tickticktick thing.
Dinosaur makes replacement control boards that also add fan control. They can usually be found for around 100 bucks:
http://www.dinosaurelectronics.com/Ignitor_boards.htm
chasespeed
Explorer
Okay, I am not familiar with this model, BUT....this is my trade
EDIT.... just found the manual.
It doesnt show a wiring diagram, just a parts schematic....
The Combustion blower, is on the same motor as the room blower... so....
ON a call for heat, the blower should fire. This SHOULD move a micro switch(not sure until I can find some wiring diagrams), which, would then allow the GV to open, at the same time the spark starts....
Check for power to the blower motor....
Chase
EDIT.... just found the manual.
It doesnt show a wiring diagram, just a parts schematic....
The Combustion blower, is on the same motor as the room blower... so....
ON a call for heat, the blower should fire. This SHOULD move a micro switch(not sure until I can find some wiring diagrams), which, would then allow the GV to open, at the same time the spark starts....
Check for power to the blower motor....
Chase
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I have that manual also.
When I turn on the thermostat the fan doesn't turn on. I was thinking that the microswitch might be stuck. If I could get it apart I'd be able to test and see what's getting power. Also I thought that the Gas Valve might be stuck. Any idea's how disassemble it?
Am I able to bench test it with out gas?
When I turn on the thermostat the fan doesn't turn on. I was thinking that the microswitch might be stuck. If I could get it apart I'd be able to test and see what's getting power. Also I thought that the Gas Valve might be stuck. Any idea's how disassemble it?
Am I able to bench test it with out gas?
chasespeed
Explorer
Okay... remove the t-stat. connect the 2 wires, thus eliminating the stat. Try that. if that works... replace stat.
No, do NOT attempt to tear down the GV. Those are meant to be replaced, not repaired.... End of that....
Make sure you are getting 24 v at the stat wires...
Your problem is not the GV. If that blower doesnt kick on, the GV wont open.
Chase
No, do NOT attempt to tear down the GV. Those are meant to be replaced, not repaired.... End of that....
Make sure you are getting 24 v at the stat wires...
Your problem is not the GV. If that blower doesnt kick on, the GV wont open.
Chase
Engineer Guy
New member
Furnace Logic
I've worked on a few Trailer Furnaces, and the operating sequence and safety components are pretty similar. If the Fan doesn't start the very first thing, as mentioned above, the failure is pretty fundamental. That is, it's not the GV.
First off, if it's a Pilot Light Model, the Pilot must be lit and the Thermocouple IN the flame must close while producing millivoltage that then allows the GV to open IF all other starting sequence conditions are met.
A Quarter-sized Thermal Switch on the Heat Plenum 'snaps' open and closed mechanically from temperature during operation like a 'Frog' clicker toy. It is Normally Closed [N.C.]. You can remove the 2 leads to it and check with an Ohmmeter that it's closed and reading only an Ohm or so. During regular operation, it controls the Flame going on and off when the Thermostat is closed, signalling for heat, and often controls Fan power, too.
A 2nd Quarter-sized Thermal Switch on the Plenum is the 'last resort' Over-temp Safely Switch. If some drastic failure occurs, that Normally Closed [N.C.] Switch opens to prevent overheating and fire. You can remove that Switch; attach an Ohmmeter; and heat it with a match to hear and see that it opens when heated. If either of these Snap Switches are bad, ain't nuttin' gonna happen - even at Heat Cycle/Fan start up - since the Control Voltage path is not intact.
Sometimes these Switches have +12 VDC wired directly through them. Other times they are wired to the Control PCB and subsequently control 'low' Voltage to a controlling GV Relay, etc.. I've scuffed up and cleaned Relay pads, since they arc and pit upon opening while breaking voltage.
The Sail Switch is a microswitch that closes from 'cold' air flow when the Blower and/or Combustion Fan starts initially. It then passes a necessary voltage to the Control PCB to allow the GV to open, and the Ignitor to fire within 'x' attempts so raw Gas doesn't flood out endlessly.
One initial 'blind faith' step I've used often is to remove Spade Lugs and clean connections with a pink Pencil Eraser or 'Scotchbrite' Pad. Furnaces live a tough life of heat and vibration. Clean and re-make any +12 VDC and/or wire-nutted Ground connections too, just on blind faith. Check for low voltages being present every step of the way. That is, if there's no voltage to the Fan, it won't blow air and the Sail Switch won't close to allow further turn on sequence progress, etc.... I've also unscrewed and cleaned up the Pilot Light Thermocouple end at the GV 'box' end on old Furnaces and Water Heaters to ensure connectivity.
I've retrofitted a Dinosaur Control Board, and they're tops. I had to modify mine, since the Furnace control was not in the +12 VDC circuit path; it was in the Ground path. Those Control Boards try 3 times to start the Furnace and give up until +12 VDC power is disconnected and reconnected. This prevents running down Batteries if Propane isn't present; a brilliant feature.
From my experience on how Model numbers are assigned, the '12' and '16' Furnace numbers likely refer to BTUs: 12,000 vs. 16,000. A Schematic for one Model likely will be useful for the other Model.
In my decades of experience, mechanical things fail first [Fan, Sail Switch, Snap Switches, and connections]. Focus on them first. The Ignitor, firing high Voltage like a Vehicle Ignition Coil, suffers insulation breakdowns and heat-caused corrosion to Chassis Ground. You can often see them operate through a viewport IF you get the Fan initialized. For my troubleshooting setup OUTSIDE, I adapted a Cooktop Gas [Appliance] feed hose to connect to the Furnace and used a BBQ Gas Tank w/proper Regulator. +12 VDC operating voltage came from an ancient Sears Battery Charger. BE SURE to regulate down to the proper Gas pressure; there's 'high' and 'low' pressure Regulators in the Propane World. The usual Disclaimers apply here. My repairs were on older, mechanically-controlled Furnaces; not Digital Sensor Furnaces.
-5 to -15 degrees this NY Eve in W. CO. Glad the Solar House is done, even though Trailer living during construction was mostly good fun.
I've worked on a few Trailer Furnaces, and the operating sequence and safety components are pretty similar. If the Fan doesn't start the very first thing, as mentioned above, the failure is pretty fundamental. That is, it's not the GV.
First off, if it's a Pilot Light Model, the Pilot must be lit and the Thermocouple IN the flame must close while producing millivoltage that then allows the GV to open IF all other starting sequence conditions are met.
A Quarter-sized Thermal Switch on the Heat Plenum 'snaps' open and closed mechanically from temperature during operation like a 'Frog' clicker toy. It is Normally Closed [N.C.]. You can remove the 2 leads to it and check with an Ohmmeter that it's closed and reading only an Ohm or so. During regular operation, it controls the Flame going on and off when the Thermostat is closed, signalling for heat, and often controls Fan power, too.
A 2nd Quarter-sized Thermal Switch on the Plenum is the 'last resort' Over-temp Safely Switch. If some drastic failure occurs, that Normally Closed [N.C.] Switch opens to prevent overheating and fire. You can remove that Switch; attach an Ohmmeter; and heat it with a match to hear and see that it opens when heated. If either of these Snap Switches are bad, ain't nuttin' gonna happen - even at Heat Cycle/Fan start up - since the Control Voltage path is not intact.
Sometimes these Switches have +12 VDC wired directly through them. Other times they are wired to the Control PCB and subsequently control 'low' Voltage to a controlling GV Relay, etc.. I've scuffed up and cleaned Relay pads, since they arc and pit upon opening while breaking voltage.
The Sail Switch is a microswitch that closes from 'cold' air flow when the Blower and/or Combustion Fan starts initially. It then passes a necessary voltage to the Control PCB to allow the GV to open, and the Ignitor to fire within 'x' attempts so raw Gas doesn't flood out endlessly.
One initial 'blind faith' step I've used often is to remove Spade Lugs and clean connections with a pink Pencil Eraser or 'Scotchbrite' Pad. Furnaces live a tough life of heat and vibration. Clean and re-make any +12 VDC and/or wire-nutted Ground connections too, just on blind faith. Check for low voltages being present every step of the way. That is, if there's no voltage to the Fan, it won't blow air and the Sail Switch won't close to allow further turn on sequence progress, etc.... I've also unscrewed and cleaned up the Pilot Light Thermocouple end at the GV 'box' end on old Furnaces and Water Heaters to ensure connectivity.
I've retrofitted a Dinosaur Control Board, and they're tops. I had to modify mine, since the Furnace control was not in the +12 VDC circuit path; it was in the Ground path. Those Control Boards try 3 times to start the Furnace and give up until +12 VDC power is disconnected and reconnected. This prevents running down Batteries if Propane isn't present; a brilliant feature.
From my experience on how Model numbers are assigned, the '12' and '16' Furnace numbers likely refer to BTUs: 12,000 vs. 16,000. A Schematic for one Model likely will be useful for the other Model.
In my decades of experience, mechanical things fail first [Fan, Sail Switch, Snap Switches, and connections]. Focus on them first. The Ignitor, firing high Voltage like a Vehicle Ignition Coil, suffers insulation breakdowns and heat-caused corrosion to Chassis Ground. You can often see them operate through a viewport IF you get the Fan initialized. For my troubleshooting setup OUTSIDE, I adapted a Cooktop Gas [Appliance] feed hose to connect to the Furnace and used a BBQ Gas Tank w/proper Regulator. +12 VDC operating voltage came from an ancient Sears Battery Charger. BE SURE to regulate down to the proper Gas pressure; there's 'high' and 'low' pressure Regulators in the Propane World. The usual Disclaimers apply here. My repairs were on older, mechanically-controlled Furnaces; not Digital Sensor Furnaces.
-5 to -15 degrees this NY Eve in W. CO. Glad the Solar House is done, even though Trailer living during construction was mostly good fun.
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PhulesAU
Explorer
hit up www.rv.net plenty of experence to tap into.
I've finally had time to troubleshoot the furnace. It ended up being the circuit board. I tested the fan motor last night to see if it worked and it did. But today when I put the furnace back together it stopped working. The pins on the motor had lots of play. I'm guessing the contact finally broke when I was messing with it.
Thanks again for all the help :wings:
Thanks again for all the help :wings: