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 > Mystery with Suburban furnace

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Breckenridge

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Posted: 05/30/19 11:08pm Link  |  Quote  |  Print  |  Notify Moderator

Hi all, I have posted this on another site as well hoping that someone might have run into this before.
During this past trip we could not get our SF 30 to run no clicking no blower, nothing. We checked the fuse and that was in tight, removed it with pliers and it was in good condition so replaced it. Voila, the furnace started right up and worked fine for the entire trip. When we returned home we turned the furnace on to keep the lines from freezing since winter has a death grip on CO. and again it wouldn't work until we pulled the fuse and then put it back in and then it worked great. Is there a reason that we are having to pull the fuse and re seat in order to get the furnace to work, and what might the fix be? Thanks for any and all input.

cavie

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Posted: 05/31/19 01:14am Link  |  Quote  |  Print  |  Notify Moderator

sounds like a faulty control board. What you are doing is resting the controls. Try resenting the T-stat.


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Posted: 05/31/19 08:01am Link  |  Quote  |  Print  |  Notify Moderator

When you turn the propane off to travel you are leaving the heater on and it is locking out

wa8yxm

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Posted: 05/31/19 04:00pm Link  |  Quote  |  Print  |  Notify Moderator

I see two possible issues:
The control board is ALWAYS a possible cause

The fuse and its socket.. There may be a bit of corrosion or in some cases the fuse may have actually have a "Break" and pulling and re-inserting is "Making" the circuit. driving and vibration breaking it.

Step one is try a DIFFERENT fuse. (new).. Cheaper than a new control board.

THen you break out the credit card [emoticon]


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RLS7201

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Posted: 05/31/19 04:52pm Link  |  Quote  |  Print  |  Notify Moderator

My SF 35 does the same as your furnace. It's not the thermostat. It's not the fuse and wiring. What I find is that when the furnace runs for an extended period of time it shuts down and will not restart. Like you I have to pull the fuse and reinsert to get the furnace working again. This would indicate the high limit switch is shutting the system down. I have added duct work so I'm convinced that I have plenty of air flow. Time permitting, I will find and replace the high limit switch.
Wiring schematic.

Richard


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Posted: 05/31/19 04:57pm Link  |  Quote  |  Print  |  Notify Moderator

I believe, from what we have experienced an what many have posted here and elsewhere, of various electrical problems that minor or not so minor corrosion is a major culprit in our RVs.
We have stored ours indoors dry and warm for many years and since then no electrical problems, that I remember. Thermostats, control boards, fuses, plus vermin. Before then the thermostat was a headache for a long while. Points just like an old car ignition and just a bit of moisture, especially when it is warm/hot and humid stored outside. A dehumidifier would be a sound investment, I believe.
Notice all the moisture on the glass and everywhere inside in winter especially when it is wet. I don't know if they integrate dehumidifiers in the new coaches or not but it would be a good selling point, to experienced RVers I think.

mapguy

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Posted: 05/31/19 05:07pm Link  |  Quote  |  Print  |  Notify Moderator

HEAT RELATED FAULT ON CONTROL BOARD. PULLING FUSE RESETS THE CONTROL BOARD.

REPLACE WITH A DINOSAUER BRAND CONTROL BOARD AND CONSIDER MOUNTING IN A REMOTE LOCATION. SEE THE DINOSAUER WEBSITE:
http://www.dinosaurelectronics.com/Ignitor_boards.htm

dougrainer

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Posted: 05/31/19 06:56pm Link  |  Quote  |  Print  |  Notify Moderator

RLS7201 wrote:

My SF 35 does the same as your furnace. It's not the thermostat. It's not the fuse and wiring. What I find is that when the furnace runs for an extended period of time it shuts down and will not restart. Like you I have to pull the fuse and reinsert to get the furnace working again. This would indicate the high limit switch is shutting the system down. I have added duct work so I'm convinced that I have plenty of air flow. Time permitting, I will find and replace the high limit switch.
Wiring schematic.

Richard


Pulling the fuse or resetting the Tstat will NOT reset a Hi Limit switch. They will sometimes reset on their own or jostling the furnace mechanically may reset the Hi limit. But just disconnecting power will not reset it. It is a bi metal switch. Once it cools down will normally reset. Yes, GOOD air flow will prevent intermitant tripping of the Hi limit. To the OP, replace the control board. It has defective logic. Doug

RLS7201

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Posted: 05/31/19 10:25pm Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

RLS7201 wrote:

My SF 35 does the same as your furnace. It's not the thermostat. It's not the fuse and wiring. What I find is that when the furnace runs for an extended period of time it shuts down and will not restart. Like you I have to pull the fuse and reinsert to get the furnace working again. This would indicate the high limit switch is shutting the system down. I have added duct work so I'm convinced that I have plenty of air flow. Time permitting, I will find and replace the high limit switch.
Wiring schematic.

Richard


Pulling the fuse or resetting the Tstat will NOT reset a Hi Limit switch. They will sometimes reset on their own or jostling the furnace mechanically may reset the Hi limit. But just disconnecting power will not reset it. It is a bi metal switch. Once it cools down will normally reset. Yes, GOOD air flow will prevent intermitant tripping of the Hi limit. To the OP, replace the control board. It has defective logic. Doug


It was not my intentions to indicate the high limit switch was resetable. Note I said "shut the system down". Hopefully you don't consider the high limit switch the system. I know it's nothing more than a bimetal device. But if the high limit switch does trip, won't that cause the circuit board to lock out?

Richard

dougrainer

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Posted: 06/01/19 06:59am Link  |  Quote  |  Print  |  Notify Moderator

RLS7201 wrote:

dougrainer wrote:

RLS7201 wrote:

My SF 35 does the same as your furnace. It's not the thermostat. It's not the fuse and wiring. What I find is that when the furnace runs for an extended period of time it shuts down and will not restart. Like you I have to pull the fuse and reinsert to get the furnace working again. This would indicate the high limit switch is shutting the system down. I have added duct work so I'm convinced that I have plenty of air flow. Time permitting, I will find and replace the high limit switch.
Wiring schematic.

Richard


Pulling the fuse or resetting the Tstat will NOT reset a Hi Limit switch. They will sometimes reset on their own or jostling the furnace mechanically may reset the Hi limit. But just disconnecting power will not reset it. It is a bi metal switch. Once it cools down will normally reset. Yes, GOOD air flow will prevent intermitant tripping of the Hi limit. To the OP, replace the control board. It has defective logic. Doug


It was not my intentions to indicate the high limit switch was resetable. Note I said "shut the system down". Hopefully you don't consider the high limit switch the system. I know it's nothing more than a bimetal device. But if the high limit switch does trip, won't that cause the circuit board to lock out?

Richard


No, it will not cause lock out. Because, the power must go THRU the Limit switch to get to the Circuit Board to start an Ignition sequence. Lock is caused by the 3 attempts at ignition and 3 failures. The Circuit Board needs to be replaced. Doug

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