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Old 11-22-2019, 06:34 AM   #21
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John, I did that test on the AC fan as you explained. I have 2 wires on my Tstat however. With switch set to heat, fan set to auto, generator running, the fan was running of course. I removed the orange low speed fan wire, it didnít stop. I did the same with the high speed wire, it didnít stop.
I replaced the wires back to normal then went to step two where I separated the blue high speed fan wires hanging out of the AC panel box. The fan stopped. I reconnected those blue wires then did the same thing using the orange low speed wires, the fan stopped.
I reconnected all wires then installed the new Dometic Tstat I just bought. Unfortunately when all hooked up everything worked the same as on the old one. Still no signal being sent to
furnace relay that we jumped before . It did correct the calibration on the temp setting however. Before the sliding lever had to get to near 85 before the click, now with the new one it clicks at near 70 which was the inside temp.

So what is this telling us John? Bad circuit board in the AC box? Anything more I can test.

Ralph
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Old 11-22-2019, 08:10 AM   #22
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Quote:
Originally Posted by relouks View Post
With switch set to heat, fan set to auto, generator running, the fan was running of course. I removed the orange low speed fan wire, it didn’t stop. I did the same with the high speed wire, it didn’t stop.

I replaced the wires back to normal then went to step two where I separated the blue high speed fan wires hanging out of the AC panel box. The fan stopped. I reconnected those blue wires then did the same thing using the orange low speed wires, the fan stopped.
Hi Ralph,

You did good on testing this. What you are describing now points to the thermostat wiring being an issue. The way that Dometic AC control board works, it is looking for a good connection (continuity) path to ground ( - 12 VDC) as a run/control signal.

I suspect somewhere inside the thermostat cable itself, somehow it got rubbed through or chewed through, the wire insulation and is connecting the fan run signal to the ground (again - 12 volts DC) inside the cable bundle itself. The normal T stat wire insulation is very soft and does not take much to break through or stretch through it. That is, if yours is normal T stat wire. Your pic of the T stat looked a lot thicker than the normal T stat wire. This wire issue could explain why the furnace does not work too. I would say you need to sort out the wiring issue first, then we go to the PC board.

If you want to test that this is happening to be 100% sure, if your meter has ohms on it, you can set up a continuity test to see if the blue and orange fan wires have continuity to the GND wire. (I think GND is black on yours from your 1 pic) You may need to unhook both ends of the wire to get a confirmed test on this as the PC board may have some small path internally. If either the fan hi or fan low have continuity to the GND wire with nothing hooked to it, the wires are being cross in the wall somewhere. You can even check the furnace signal wire too as well as the others. If you do not get continuity to GND, then check if the wire itself has continuity. The wire could be chewed open.

This must be the fall season for this wiring issue. Club member ScottK just had this issue, except in his case, the issue is on the wire from the AC unit control box down to the furnace. He has evidence critters are up in his attic. See here for more http://www.sunlineclub.com/forums/f7...ing-19529.html

I your case, this may be a little easier to deal with pending your T stat location in relation to the AC unit. It sounds like you need to replace the T stat cable with a new one. Odds are high you cannot fish it through the wall to hide it. You may have to attach it out in the living space to the wall and up to the AC unit and connect it in a neat manner. Local hardware stores or lumber yards have multi conductor T stat wire. That may not have the 6 conductor or more cable you need, and have to get 2 cables to complete the fix. 4 wire is maybe more common, then 6 or more conductor. Or just do a temporary fix with 2 cables to get it hooked up and later order a 6 or more signal cable and make it more permanent.

If you want to test that the wires are the issue, just hang a test wire or new wires out in the open, hook it up and see that it fixes the issues.

Good luck and let us know how it goes.

John
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Old 11-24-2019, 05:34 PM   #23
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Okay John. I will next try a temporary replacement of the wires from Tstat to AC panel. It kind of makes sense it could be chewed wires as I did hear mice in the wall some time back before I set out a snack of Dcon.
It is winter time here now so I have closed up the camper for the winter, took batteries home, etc. Unless I decide to go up again this season, I'll probably suspend work on this problem until the spring.
Do you know if this lengthy post will remain on the forum for that time period. I would hate to lose it all. I could print it out but seems none of the photos print when I tried that.
I read the other guys issues with the same problem, sounds very similiar.
So thanks for all your help to get this narrowed down. I'll be sure to keep you up to date on my progress.
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Old 11-25-2019, 05:02 PM   #24
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Hi Ralph,

Your post will stay up all the time. We do no delete posts unless there is a special need to. Your post will help others in the future with similar problems.

You mentioned again that you cannot print and get the pictures to show, h'mm something does not sound right. I just tried it and the pics view in my print preview.

How are you going about printing? I open the thread I want to print, I mouse right click, select print and I get the whole thread with pics for page 1. To get the rest, I go to page 2, and do it again for the rest of them.

Let me know how you are trying to do your printing, and are you using a Windows based PC or a MAC? I can get admin to help if needed.

On the wiring, OK we can pick this trouble shooting back up in the spring.
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Old 04-04-2020, 11:51 AM   #25
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Good Spring John. Well, it would be a good spring if it wasn't for that darn virus going around. Hope you are well. There are no deaths in our county here in Saginaw MI, so we are doing okay.
Last we talked, I said I would get new wires and do what you suggested which was to jump directly from the thermostat to the AC box to try to eliminate the possibility that one or more wires on that route are bad. Note that on the original wires, the white (furnace) wire was only sending about 6 volts between the Thermo and the AC.
I ran a new white wire, and noticed right away it was now 12.5 volts! Tried to get the furnace to run, but nothing. I went ahead and did the same with all 6 wires, still nothing. After a couple hours of checking connections and fuses, I saw that the 20amp (furnace) fuse in the converter box was blown. (this was not blown last fall when we were doing various tests). Tried the furnace again, still nothing.
THEN, I noticed that the thermostat had an additional switch position. With the cover on, it was up for cool, down for heat, center for off. However with cover off there was a 4th position to the downward direction-- I'm guessing it is also an "off". I was so used to just pushing the switch down to put it on heat, that with the cover off it was going past the heat setting and into the bottom off setting. With the cover on, the cover would not let the switch go down that far, it would stop on heat.
So when I moved it to heat, the furnace blower started after 30 seconds, then the burner started a few seconds later. Problem fixed.
I'm thinking the whole problem is that damaged white wire running from the thermostat to the AC box, probably mice as you say, and only letting 5 or 6 volts thru rather than 12 or 13. Probably not enough voltage to start things going. Does that all make sense to you?
The original wiring had a brown wire running along with the 6 others that wasn't connected to anything, so I was able to substitute that for my white wire and not have to run the new cable inside the ceiling and walls. All the other wires had good continuity and all is working fine. i then spent a lot of time getting everything back together and cleaned up.
Thank you so much for all your help. I have learned so much with this whole issue that maybe someday I can help someone else out.


Ralph Louks
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Old 04-04-2020, 10:00 PM   #26
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Hi Ralph,

Great! you have it all working. Good for you.

The 4 position switch, the 4th position, the furthest down is for a heat strip option. You can add a 120VAC electric heat coil that mounts up above the ceiling of the AC air duct unit. It would go next to the silver electrical box with the control board. In this mode, the furnace does not run, but the electric element does and the heat blows out where the cold air ducts are all controlled by the T stat. I forget the exact wattage of the element, I think it is in the 800 to 1,000 watt range. Not enough to heat the camper on a cold day, but enough to take the chill off on a fall or spring day.

Here are 2 pics of where the wires on the T stat go for the heat strip. This T stat does not have the feature but does have future space on the PC board if it was ordered with the T stat. See the HS (heat strip) lettering above the TB1 lettering on the left. That would have a terminal and a wire for it to run up to the control board.


And here on the wiring diagram, there is a 4th position to the selector switch called HS which you found that does shut off the furnace and would turn on the control for the heat strip.


The extra wire Sunline installed may have come as standard for the heat strip option and they just did not use it if it was not ordered. Some of the Sunlines did come with the heat strip if ordered with the camper.

And yes, with a blown fuse and the white wire passing low voltage, it points to something affected the white wire.

You did good on the troubleshooting and you now know how the whole system works for the future. It has been said, you learn a lot more when things so not work right then when they do!

Thanks for reporting back and have a good camping season whenever it starts back up.

John

PS. Thanks, all of my family and I are doing well health wise with the virus situation. Thanks for asking.
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