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Old 11-13-2018, 06:38 AM   #21
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Brand: Thor Motor Coach
Model: Four Winds 30D
State: New Jersey
Posts: 26
THOR #13701
Quote:
Originally Posted by javelin View Post
Well at least you or family have not frozen....yet. The main thing is to make sure your pipes don’t freeze in the coach.....people can huddle around a space heater or put on more clothes to stay warm. You may want to call a mobile tech as that may be less costly than a major freeze and water leak in your coach..... or a divorce. LOL.


In the mean time, if the weather permits (no rain/low winds), I would be tempted to leave the furnace door off in the day time while you standby for it to fail again.......and then carefully move select “start circuit” wires (like +12v and ground; on off reset switch or thermostat or control board; motor) in the furnace area to determine if/when the fan starts up (during a constant thermostat call for heat of course). If no intermittant wiring trouble is found then try your tapping technique around furnace devices to home in on the fault location.


You said previously that you measured a few volts only (between red to blue on the inside thermostat during the failure time – which is essentially +12V and ground per your schematic). For voltage to drop to a couple volts (implies high current loading or high resistance intermittant connections) is not normal especially with no apparent fuse blow or smoking components. Maybe just a bad meter reading ......or flakey high resistance +12v or ground wire connection or wire conductor itself causing intermittant high resistance conditions.


One other option which requires the +12 feed turned off to the furnace (fuse pull best at source) is to use the ohmmeter setting on your multimeter and place it across individual wires that should provide short ccts (low resistance on the meter) and then wiggle each wire being measured to see if the meter reading changes). This could indicate a bad wire or broken conductor inside the insulation. It is best to have small alligator clips on the meter leads so you can clip on each wire end and wiggle wires. Ohmmeter readings must be taken on dead circuits – reading a live circuit will potentially damage your meter. Remember to reset meter to read volts again when you are done with any ohmmeter tests.
That’s about all I can suggest.
First, I really appreciate your input... we are astounded by the responses by you and others who have offered insight. Its an awkward and lonely feeling camping for the first time in our new (and not cheap) RV to have to worry about keeping warm and not frozen or more importantly, keeping the coach from causing damage by frozen lines. Wife and family are OK, although not the best experience for them the first time out. Not sure I can speak for my neighbors at the camp site that may have caught a glimpse of me running out in the middle of the night/early morning in my boxer shorts and slippers to give my furnace a kickstart/thump.... just glad it wasnt captured on Funniest home videos!!!

We decided to head back home after Sunday for fear my "Heat thump" jumpstart might stop working... We are home now in NJ, expecting some stormy weather later today, I decided to winterize the coach (blew out the water lines/pump and antifreezed the traps) as it may be a few weeks before we opt to take her out again. Ironically the furnace worked today without need for my thump, I was hoping it would fail so I could take some more measurements. It was a little warmer today, so maybe once it cools down over the next few days I will see if I can recreate the failure and take the measurements as noted.

I did post a link to videos showing the issue (used Youtube posts) earlier post.

Once again, Thank you.

Dave.
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Old 11-13-2018, 02:05 PM   #22
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Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 560
THOR #2631
Well Jevad, I viewed your excellent videos. Well done. Now if only the forum can help translate them into a solution for you. Although I don’t have a Coleman Mac thermostat schematic I think it is fair to say that when the +12vdc feed (red wire) on the thermostat is only reading 2 VDC, the call for heat relay in the thermostat is not going to operate (click on) properly or at all to connect red to white wire and actually call for heat at the furnace end.
So to me the issue is why the 12vdc is dropping to 2ish vdc? Maybe the power/reset switch in the furnace is flaky with damaged/dirty or just poor contacts inside? Strange because it hardly gets used. When you have “your problem” occurring measure feeder (coach fuse) side voltage on the furnace switch. Should be 2 vdc (based on schematic) if trouble is on. Then turn off the switch and see what you measure. Jumps up to 12vdc then the issue is on the furnace side of the switch......or the switch itself. In effect you need to isolate where the flaky part/wire/splice/crimp/connector is occurring. Since bumping the area seems to fix the intermittant problem this could take a while to track down. I would also operate the switch several times if it looks to be the culprit. You could also temporarily jumper the switch and see if the trouble stops occurring. Don’t you just love those intermittant problems? Don’t give up now you are home and winterized.
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Old 11-13-2018, 03:40 PM   #23
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THOR #2631
After re-reading my last post I think “if” the on/off switch at the furnace was flaky with a high resistance contact closure the furnace side of the switch (including the Coleman Mac red lead contact )would have the 2vdc problem voltage, but the main coach 12vdc feed to the switch should still be 12vdc. A temporary jumper across the switch would prove the switch is or is not the problem long term.
Another thing to try: if the sail switch occasionally sticks in the “prove” blower is running position, (typically might happen after the furnace has shut down after a normal cycle); you could temporarily disconnect the sail switch (tape over the loose wire end so it does not touch anything else) and see if your trouble voltage situation ever re-appears. Just wondering if the control board drags the 12vdc line down to 2 vdc when the sail switch sticks closed and always passes 12vdc to the blower running sense port of the control board. The only issue with sail switch disconnect is the blower will start but you should never get to the flame ignition/heat stage and the blower will just shut off. Its only a temporary situation though. Just be careful disconnecting connectors....you do not want to break off a microswitch connection or you will be doing a lot more work and cost to repair.
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Old 11-13-2018, 04:37 PM   #24
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Brand: Thor Motor Coach
Model: Four Winds 30D
State: New Jersey
Posts: 26
THOR #13701
Quote:
Originally Posted by javelin View Post
After re-reading my last post I think “if” the on/off switch at the furnace was flaky with a high resistance contact closure the furnace side of the switch (including the Coleman Mac red lead contact )would have the 2vdc problem voltage, but the main coach 12vdc feed to the switch should still be 12vdc. A temporary jumper across the switch would prove the switch is or is not the problem long term.
Another thing to try: if the sail switch occasionally sticks in the “prove” blower is running position, (typically might happen after the furnace has shut down after a normal cycle); you could temporarily disconnect the sail switch (tape over the loose wire end so it does not touch anything else) and see if your trouble voltage situation ever re-appears. Just wondering if the control board drags the 12vdc line down to 2 vdc when the sail switch sticks closed and always passes 12vdc to the blower running sense port of the control board. The only issue with sail switch disconnect is the blower will start but you should never get to the flame ignition/heat stage and the blower will just shut off. Its only a temporary situation though. Just be careful disconnecting connectors....you do not want to break off a microswitch connection or you will be doing a lot more work and cost to repair.
Thanks Javelin, no worries I'm gonna keep trying to debug, and will be sure to post what I find. The intermittent problem is frustrating, and somehow only seems to show up in the middle of the night or snow storm...

I'm pretty sure it isnt the Off/Reset switch, when I first looked on here for a solution, someone said it may be that switch.... the second time the failure occurred (the first time it reset as I was removing the panel). That was the first place I went, toggled the switch on and off a few times. I even unscrewed the panel to better see the diagnostic light, and check the wiring, I toggled the switch a few more times. If it was a faulty/dirty contact on the switch it certainly would have made good contact as I toggled it - especially if its easily fixed now with a light thump on the side.

I really wish it would fail now so I can debug it better with the knowledge that I have now.
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Old 11-18-2018, 01:43 PM   #25
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State: Alabama
Posts: 16
THOR #8541
Connection issue

I didn't read the complete thread. The white connector to your green control board gets some minor corrosion on the pins. You need to go to a hardware or automotive store and get some dielectric paste. Unplug the connector and put a small amount on the tip of each pin and then insert the connector several times to wipe the posts. Make sure furnace is not calling for heat when you do this. It has worked for me every time I have an issue with someone's furnace. Once I did have to order and replace the control bd. I now keep a spare.
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Old 11-18-2018, 10:27 PM   #26
Luc
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THOR #3731
check your sail switch
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Old 11-19-2018, 11:31 PM   #27
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Brand: Thor Motor Coach
Model: Challenger 37KT
State: Nevada
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THOR #5937
Furnace issues

Actually have a service appointment on the 28th because furnace was not staying lit after initial light, tried to kiss KEEP IT SIMPLE STUPID the problem, and when I realized that my AC (same thermostat) wasn’t working I took a chance via Amazon and replaced the thermostat and as of this reply feeling like a genius LOL BOTH are working great( if changing out the thermostat, take your time and change one wire set at a time, I am old and needed to move slowly on this, about 45 minutes but as of right now very happy with the results
Trying to decide if want to go back in and solder all the connections or live with wire nuts alone
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Old 11-26-2018, 04:41 PM   #28
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THOR #13701
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Originally Posted by tmtube View Post
Actually have a service appointment on the 28th because furnace was not staying lit after initial light, tried to kiss KEEP IT SIMPLE STUPID the problem, and when I realized that my AC (same thermostat) wasn’t working I took a chance via Amazon and replaced the thermostat and as of this reply feeling like a genius LOL BOTH are working great( if changing out the thermostat, take your time and change one wire set at a time, I am old and needed to move slowly on this, about 45 minutes but as of right now very happy with the results
Trying to decide if want to go back in and solder all the connections or live with wire nuts alone
Glad to hear your Thermostat swap is working well... I'm going to change mine once my current issue gets straightened out... still don't think its my thermostat, I'm leaning on its either the Sail switch and/or the Ignition control board. My experience in general, and for what its worth, wirenuts are OK, if you electrical tape each cap on to the wire (so they don't creep or unwind) - my general practice is to ALWAYS tape on top of caps in our house. Now that doesn't account for an RV where everything rattles and rolls... so I would either Solder or Crimp and Tape (likely what I will do when I put in mine.
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Old 11-26-2018, 04:44 PM   #29
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THOR #13701
Quote:
Originally Posted by Luc View Post
check your sail switch
Thanks LUC, still waiting to debug a little further, and working with the dealer for a solution. Yes, I think its probably the Sail Switch (or Ignition Control Board)... but haven't been able to recreate and confirm yet. I'll post update when I resolve.
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Old 11-26-2018, 04:49 PM   #30
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Brand: Thor Motor Coach
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THOR #13701
Quote:
Originally Posted by gordstok View Post
I didn't read the complete thread. The white connector to your green control board gets some minor corrosion on the pins. You need to go to a hardware or automotive store and get some dielectric paste. Unplug the connector and put a small amount on the tip of each pin and then insert the connector several times to wipe the posts. Make sure furnace is not calling for heat when you do this. It has worked for me every time I have an issue with someone's furnace. Once I did have to order and replace the control bd. I now keep a spare.
Thanks gordstok, I will definitely keep that in mind, and will probably add some dialetric paste to my wires. I should note, there are NO signs of any corrosion on the board or anywhere (only a year old), but its a good thing to keep an eye on. I posted pictures on an earlier post...its surprisingly clean in there.


Thanks again,


Dave.
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Old 11-26-2018, 05:04 PM   #31
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Model: ACE 30.1
State: Colorado
Posts: 337
THOR #5190
Quote:
Originally Posted by Jevad View Post
Glad to hear your Thermostat swap is working well... I'm going to change mine once my current issue gets straightened out... still don't think its my thermostat, I'm leaning on its either the Sail switch and/or the Ignition control board. My experience in general, and for what its worth, wirenuts are OK, if you electrical tape each cap on to the wire (so they don't creep or unwind) - my general practice is to ALWAYS tape on top of caps in our house. Now that doesn't account for an RV where everything rattles and rolls... so I would either Solder or Crimp and Tape (likely what I will do when I put in mine.
I've stopped using wire nuts and have gone with Ideal Connectors everywhere (12V and 120V). I understand that Thor has finally seen the light and using a similar design connector. The picture attached is where I intercepted the tank level wiring when I installed the See Level tank indicator system.
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Old 02-24-2019, 06:43 PM   #32
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Brand: Thor Motor Coach
Model: thor miramar bunk model
State: New York
Posts: 1
THOR #14527
same problem

I would love to hear how it turned out. I have what appears to be identical problem except beating on out sid edidn't fix it !
Wasn't getting 12 volts to the thermostat asnd a temporary jumper form a lite switch fixed the problem for the moment. Furnace seems to want to run, however, intermittently, regardless of whether thermostat is OFF or on heat. A little unclear on the off and reset switch. Off would seem to turn the furnace off but why you would leave it in the reset mode which I am guessing is really the run mode. I have 1 2018 Thor Miramar. Took to dealer several times and no fix. eager to ehar how your problem turned out.
Thanks
Larry
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Old 02-25-2019, 11:59 PM   #33
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Brand: Thor Motor Coach
Model: Four Winds 30D
State: New Jersey
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THOR #13701
Quote:
Originally Posted by lrplumb View Post
I would love to hear how it turned out. I have what appears to be identical problem except beating on out sid edidn't fix it !
Wasn't getting 12 volts to the thermostat asnd a temporary jumper form a lite switch fixed the problem for the moment. Furnace seems to want to run, however, intermittently, regardless of whether thermostat is OFF or on heat. A little unclear on the off and reset switch. Off would seem to turn the furnace off but why you would leave it in the reset mode which I am guessing is really the run mode. I have 1 2018 Thor Miramar. Took to dealer several times and no fix. eager to ehar how your problem turned out.
Thanks
Larry
Hi Larry, To answer the question, I'm not quite sure. I live in the North East and haven't had the RV out the last 2 winter months.... but I'm looking forward to a trip coming up. After my last trip, I let the heat run for 24 hours, without having to perform my "Heat Thump". I've also gone out and run it twice during the winter (with moving the RV, and running the generator - just for maintenance purposes) and the heat worked. I spoke with the service Tech from the place where I purchased the RV, we both kind of suspect it is the "Sail Switch" - he is sending a new one out to me since they are relatively cheap and also asked to do some further debugging (measure if the switch is stuck closed) when/if it happens again. Having the spare sail switch with me wont leave me stranded and its a quick swap out.



Your problem sounds a little different since you are able to bypass and provide 12V to the thermostat. I would try and follow the wiring diagram, IF yours is the same as mine, there is a "Reset" switch, on the furnace that FEEDS the thermostat. you may want to check that to see if its lose/triggered or a wire is lose - check the voltages there.
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Old 06-12-2019, 08:02 PM   #34
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Brand: Still Looking
State: Florida
Posts: 1
THOR #15636
33063 sail switch

Mine tested fine at 2 different repair shop but when I reinstalled furnace did not work last guy used a voltage record to see as we move rv the power went on and off at switch so waiting for a new switch try again 2019 cougar 26 rbs
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