Coleman Mach no work 2012 Navion 24j

[bigb]

I think the 12 volts goes to the furnace first, from the furnace fuse in the fuse panel, then it travels up to the thermostat where it passes through the 2 amp fuse on the back of the thermostat. This is a guess but it makes the most sense. Hopefully Tof will be able to follow/trace some wires and keep us posted.

There would be no need for a separate power supply since the thermostat in question is 12 VDC and so it the coach fuse panel.

[bigb]

This document covers several models but requires running the 12 volt negative directly from the converter or battery for 12 volt thermostats. It also says the 12 volt thermostat gets it power from a converter or battery which rules out a separate power supply.

It also shows a control box diagram that includes a heat relay which could be used to close the circuit to the gas furnace. It does not show the heat pump option but we don't need that for our present troubleshooting issue.

https://library.coleman-mach.com/wp-...6A658-3-15.pdf

[bigb]

Here is another Coleman document with some good troubleshooting flow charts and descriptions of operation. The voltages found at the thermostat should also be present up in the control box which as I mentioned may not be easy to access from below, and to access from above the shroud and the fan compartment have to be opened up.

edit: looks like there are control boxes with relays and control boxes with printed circuit boards. If the OP has a printed circuit board I suppose a board failure could prevent the entire system from working, as well as a bad power connection to the board.

The units with printed circuit boards are going to have 2 blue wires at the thermostat, one bringing the negative 12VDCin and the other bringing it up to the board.

Tof can you verify if you have 1 or 2 blue wires at the stat?

http://www.cleggind.com/postal_tech/...376%5B1%5D.pdf

[bigb]

I jumped a little ahead when I mentioned the control box, sometimes it's easy to forget a clue and jump ahead. When I mentioned the control box I forgot about the clue we were given that the thermostat went dark at one point. If that clue is accurate the problem still points to the supply of 12VDC. That supply may originate at the furnace, but it may stop at the control box first before hitting the thermostat. At any rate, that is my suspicion and can't really go further till that is proved ouI would suggest unplugging the connectors at the stat and cleaning with CRC as a first step, then tracing out the power wires. Temporary jumpers could be used to bypass the power wires as a troubleshooting tool.

[Morich]

So is my confusion about the power, only because they label it 12Volt negative and also 12Volt positive? Are they actually talking about ground, not 12Volt negative?
I can't think of any way to get 12 negative from a 12 volt positive battery system without doing some form of added power supply!

I got a little shy about trusting the drawings on RV when I saw 240 Volt AC! I think that kind of works to confuse people quite a bit!

I think I better back out if they call the negative battery post 12Volt negative. Not the way I ever see it! If you test 12 volt negative to 12Volt positive, you get 24 volts!

[bigb]

Some of the manuals show 240VAC because they were written in the European market but there is no difference in their 120VAC US models. I see this with Dometic fridge manuals all the time.
You lost me in the 12 volt. Some call it ground some call it negative. Some use the term negative to differentiate between 12VDC and 120VAC. I don't see 24VDC on the drawing, I see 12 VDC. A positive and a negative, or a positive and a ground however you call it.

[Morich]

This is where I was seeing 12volt negative as well as 12 volt positive.
the difference between 12neg and 12pos it 24?
But did they really just mean ground or negative post?
Or where do they get 12Volt negative on a 12 volt positive RV ?

[Sparky19053]

We had this issue while in FL this spring. Check for 120 volt power at the AC unit. to do this you will need to pull the outside cover. Below the cover there is a tin access panel to the power connection. You need to be sure there is 120 volts across the white and black. On our 21V we found a junction box mounted to the ceiling above the frig. There are two J boxes. The yellow wire is for the AC and is 12/2 RX. The other box has four white leads, all 14/2 RX. In my case the push in connections had failed on the AC line. In the field I removed the J Box and used some wire nuts to get the AC working. Once home I replaced both J Boxes with 4" square boxes using good quality wire nuts. No push in connectors in my stuff.

[bigb]

Originally Posted by Sparky19053

We had this issue while in FL this spring. Check for 120 volt power at the AC unit. to do this you will need to pull the outside cover. Below the cover there is a tin access panel to the power connection. You need to be sure there is 120 volts across the white and black. On our 21V we found a junction box mounted to the ceiling above the frig. There are two J boxes. The yellow wire is for the AC and is 12/2 RX. The other box has four white leads, all 14/2 RX. In my case the push in connections had failed on the AC line. In the field I removed the J Box and used some wire nuts to get the AC working. Once home I replaced both J Boxes with 4" square boxes using good quality wire nuts. No push in connectors in my stuff.

Hey fellow Sparky that makes sense for the AC/Heat pump but if you look at post #3 the gas furnace doesn't work either and that's strictly 12 volts so it's got to be in the control wiring.

[Ray,IN]

Originally Posted by bigb

Some of the manuals show 240VAC because they were written in the European market but there is no difference in their 120VAC US models. I see this with Dometic fridge manuals all the time.
You lost me in the 12 volt. Some call it ground some call it negative. Some use the term negative to differentiate between 12VDC and 120VAC. I don't see 24VDC on the drawing, I see 12 VDC. A positive and a negative, or a positive and a ground however you call it.

Brian is this the 'stat in question? https://library.coleman-mach.com/wp-...4/1976-331.pdf
and page 6 here: https://bryantrv.com/docs2/docs/rvp/6535heatpump.pdf



This issue sounds to be like a loss of ground/earth for the 'stat.

[bigb]

Originally Posted by Ray,IN

Brian is this the 'stat in question? https://library.coleman-mach.com/wp-...4/1976-331.pdf
and page 6 here: https://bryantrv.com/docs2/docs/rvp/6535heatpump.pdf



This issue sounds to be like a loss of ground/earth for the 'stat.

That's it Ray and I agree

[Brooks]

Originally Posted by Tof

Have Coleman Mach Model:48058-876 has stopped dead in its tracks. Can not reset. No digital display at thermostat. Power to coach, microwave, and to AC breaker checks OK with volt tester.

Wide open to any suggestions?

I had the same problem and after a few tries I finally bought an update Coleman Mack 9420-381 took me a little bit to figure it out but now I love it

[Brooks]

Originally Posted by Brooks

I had the same problem and after a few tries I finally bought an update Coleman Mack 9420-381 took me a little bit to figure it out but now I love it

I would of sent a link but I'm an old guy and don't know how to do that

[Fanrgs]

This is a photo of my C-M heat pump terminal block inside the control box after my AC stopped working on my 2020 Navion 24V. All the 120vac wiring burned up, apparently due to loose connections on a 3 y-o unit. You can't buy just a new trminal block, you have to replace the entire control box. For $212 from AirXcel.

I didn't replace the box; I removed the whole 90# AC from the roof. I replaced it with a 12v, 36# TurboKool evaporative cooler, similar to the evaporative coolers we have had on our Colorado houses for over 50 years. We are sitting in our cool motorhome in 87 degree Heber-Overgaard, AZ as I write this. But admittedly it didn't cool quite as well last weekend in 106 degree Las Vegas, which is a new record high for 9/29!



https://www.amazon.com/photos/shared...IYkGh1WzYYx_9v