Coleman Mach no work 2012 Navion 24j

[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?

[Morich]

A point to keep in mind on the heat and air is that the thermostat uses 12VDC as only acts as a switch to turn the 110AC on/off.
When there are no lights, etc. at the thermostat, I tend to think of 12VDC problems!
The issue is a design thing where the big air unit needs lots of power and we get it from 110AC. But those heavy wires are not nice to fit a half dozen or so into the little box on the wall. So they use little wires and power at the thermostat to control a big relay up on the AC unit where they start and stop the big wire 110AC!

If we know what year, make and floorplan you might have, there are often online drawings where we can sort out which breaker or fuse might be involved!

Maybe do a quick test to see if the furnace will start the blower when the thermostat calls for heat. Just as a generic idea, the 12Volts from the furnace may run the thermostat for both heat and cool. If the furnace blower doesn't come on right away after setting for heat, maybe a check in the "load center" where a bunch of 12Volt fuses are located may turn up one labeled for furnace?
Click this snip for better view!


Tell us which RV if we need to chase it further?
Consider this a first shot random guess!

[Tof]

First of all the contact cleaner on the fuse was a bust. No joy! Played with the furnace. It won't run gas or HP. Pulled Furnace fuse and reset. Now display but still nothing works.

I happened to note your location. My Uncle Clifford had his first teaching and coaching job there after San Marcos State. The football team had no practice field so they used local ranchers Goat pasture.

Back to problem, next move DR.

[Tof]

Have checked settings and wire terminations on the thermostat. Red wire has power. when you move the controls to fan or any other position nothing happens or no current. Since this old one is not an electrical genius how do we determine a faulty thermostat?

[Morich]

I try to go the easy way when it seems as good as the hard way. When faced with looking at an air unit which may be on the roof or a furnace which is down where I can get to it, I look at the furnace as the easy one!
so if we move into looking at the furnace, can you locate a label on the furnace that tells what brand and model it might be?
As an alternate, do you have booklet for the furnace in a bag of books for the RV? That might also tell us what we need.

As background info, the idea is that the power wires from the batteries to the furnace fuse and then it also goes on different wires to the thermostat. The thermostat acts as different switches by the way we set it. When we set the thermostat to heat, The power you are seeing comes from the heater to to the thermostat. When the temperature calls for heat, that power is sent back to a board on the furnace to make the blower start running.
I don't know the furnaces all well enough to tell you where to look for that power coming back. We know 12volt is good and getting to the thermostat, but we don't know why it is not making the furnace fan come on!
If we can locate the right manual for the brand and model of furnace, we can then likely find a drawing to show where to look at the power coming back!

Maybe think of it this way as we do it more?
We have a switch on the wall and we know power is getting to that switch but the light doesn't come on like we expect it when we turn on the switch!
So we have to find out if the wire is bad or if the power is getting back and maybe the bulb in the light is bad!
Only in your case the switch is a thermostat and a blower on the furnace instead of the light bulb!

OR?
If not finding the furnace info, does the thermostat have any brand or model where we might look for a manual for it?
The connections are often not marked to tell us which wire does each thing but maybe we could find a book with that info?

[Tof]

The coach is a 2012 Navion 24j
Ac is a Coleman Mach Model 48058-876
Thermostat is an RVComfort.HP Mach 8530-3381 Digital Heat Pump RV Thermostat. Which by the way wouldn't you just know it is discontinued?
The Ceiling Control box is 8530B7332

[bigb]

Originally Posted by Tof

Have checked settings and wire terminations on the thermostat. Red wire has power. when you move the controls to fan or any other position nothing happens or no current. Since this old one is not an electrical genius how do we determine a faulty thermostat?

Have you pulled it off the wall and checked all the connections and all the wires? You say you got the display to come back, but when you try to switch to a cooling or heating mose does that display go dark again?

I would be looking at the connections, especially the ground connection. I have that same thermostat a year older than yours, it's a pretty simple device and it has been pretty bulletproof, there is not that much that can go wrong with it which makes me suspect a connection issue.

[Morich]

Well, this is not good! I've run the thermostat number down to this site for manuals but not getting any good info:
https://library.coleman-mach.com/
When scrolling down to the correct model and hitting download, it simply takes me in a circle back tot eh same page!

I'm not sure what to make of that. Is the page being rebuilt? Is the info dropped for some reason or did the company decide totally to ignore the issue?

I have to say I am now totally at a dead end without being able to get info. Certainly no heat and air guy but normally just have to go in and study the way it works but without the manuals and info, I'm dead!

Sorry, but I think I'm no help!

[Tof]

Will pull that little jewel off of the wall first thing in the morning, open each connection and spray well with contact cleaner.
To be honest have not observed the display when switching. Will check that also.

[bigb]

Originally Posted by Tof

Will pull that little jewel off of the wall first thing in the morning, open each connection and spray well with contact cleaner.
To be honest have not observed the display when switching. Will check that also.

If the display goes dark when you try and switch something on you have a bad connection on the power or ground (or a dead house battery, you did check for 12 volt power in the coach right?).

Also look in your manual packet, mine has a brochure for the thermostat. I don't recall if it covers installation or if it's just a user manual though.

[bigb]

This covers the 8530 series

[Tof]

Bigb Many thanks for the user manual. None came with the unit when we purchased it.

[Morich]

Yes, that is a definite help as it gives where we should expect to find a negative and positive 12Volts.
Need to check for both, I assume?
Not totally clear on the operation, though! does switching the thermostat to heat then send 12 volts back tot eh board on the furnace to tell it to start the blower?


Some checking needed on that but something has to tell the furnace to come alive!

[Tof]

Something keeps nagging at me that the whole thing is a control box failure. The current is present showing 13 volts on the voltmeter. If the thermostat is not tripping something to do its 120-volt thing then that breakdown would certainly rest in the failure of the control box. Am I just chasing the wrong dog?

[bigb]

Originally Posted by Tof

Something keeps nagging at me that the whole thing is a control box failure. The current is present showing 13 volts on the voltmeter. If the thermostat is not tripping something to do its 120-volt thing then that breakdown would certainly rest in the failure of the control box. Am I just chasing the wrong dog?

Maybe. Does the voltage connect to the different output terminals on the T-stat when you select one?

You probably have a module with a terminal block up in the AC unit that you can see if you remove the grill and filter, you could check up there for any loose or damaged connections next. It's kind of tricky to get to as it's right near the top but the evaporator is only a few inches away from it.

[bigb]

What points to the thermostat or thermostat wiring is the fact that neither the furnace or the AC/heat pump works. I honestly don't know if there is a control box that is common to both, it looks to me like the white wire just heads off to the furnace and the remaining wires go to the rooftop unit. Maybe if you follow the T-stat cable to it's first stop you will see where the white wire splits off to the furnace and inspect things there. The cable may go to the furnace first, or the AC first but one way or another that white wire has to split off.

This diagram shows what I mean even though it doesn't include a heat pump.

The 12V + & - may also be common to both the stat and the furnace and an interruption at either could cause nothing to work. For instance the 12 volts could start at the furnace then go up to the stat.

[Morich]

Wow! Glad to see somebody else is looking at this as I just got a news flash on how far off I can be when I look at a different set of drawings from different equipment!

I'll tell you this but only if you are far enough away that I can't hear you laugh!!


I was really totally boggled about what the drawing I posted was trying to tell me as the equipment did not seem to make any sense!

Somedays, I'm not fully awake! But I had a terrible time seeing what equipment they were showing connections on!
Turns out with a new look, they are not showing equipment but just the plugs! DUH!


This might be easy if you can look at the stuff we see on the drawings??
I now see a four pin male plug with only three wires and a second four pin female plug with four wires and that likely means they DO NOT plug to each other but different wiring!

Permission granted to laugh!

[bigb]

Richard, the plugs come with the thermostat so the RV builders can just plug the harnesses together without having to have any HVAC wiring knowledge, or make any mistakes.

[Morich]

You mentioned getting 12 volts at the thermostat? Did you get both positive and negative 12Volts as this shows?

Negative at "B-" ( Blue Wire?) and positive 12 at "R" (red wire?)

If that is true, what is the triangle in a circle and is that a white wire from the furnace?
At the thermostat, I think of wires soldered to a board on the thermostat and those wires often meet Winnebago wires at connectors maybe 5-6 inches out and tucked down in the wall. Finding anything like that?
If you find Winnebago wires and they are labeled as their "standard", that might be a help if we found the wire ID as this chart:

https://www.winnebago.com/Files/File...ical_guide.pdf
If finding the Winn ID on wires, the chart then tells gauge and color as well as the "from" and "to" locations for that wire! But it is likely to be a different Code than this drawing.
Using GH and GL for green and grey seems a little random for me! But I'm not a heat and air guy!

[Morich]

Any thoughts on where they hid a power supply to put out the negative and positive 12Volts?