Forum Discussion

ChaosAgent's avatar
ChaosAgent
Explorer
Mar 31, 2016

1999 American Eagle AC Control Box

Last August I replaced the original Coleman Mach V AC in our 1999 American Eagle with a Coleman Mach 15. It has worked great since then, and the increased cooling is noticeable.

But a couple of days ago, it quit cooling. Fan works, but no compressor.

Checking out the unit from inside, I found that I'm not getting 12 volts on the yellow wire that controls the compressor.

So I swapped out the Honeywell Thermostat control with the bedroom AC one. But it continued to work fine, and the front one still didn't.

So checking the voltages at the thermostat base plate on the rear unit, I have 12 volts on the Heater, Compressor and Fan connections.

But up front, I have 12v, 5.92v and 12. So only ~6v on the compressor wire. Which of course is the problem.

And FWIW, the 12 volts actually seems to coach battery voltage, since it can sometimes be 12.96, or 13.25. And the 5.92 can be 4.7, or even 1.4v.

So next I checked continuity between the 12v connection on the baseplate, and got a complete open.

OK, so what's in-between? Where does the 12 v on the thermostats coming from. It's not coming from the AC unit, because turning off the breaker still leaves the 12 volts on both units.

So the 12 volts is coming from somewhere else, and is in between the compressor connection on the thermostat and the unit's control box, since I don't have continuity.

American Coach tells me that there is another control box in the rig somewhere, but the location is unclear. First they told me it was in the duct 'under' the AC unit. Then they said that it was in the duct somewhere.

Well, I have a 2" x 10" duct running the length of the coach, connecting the two units. I took off a couple of vents and took photos going in both directions and there's no control box to be seen.

So does anyone have any idea about where this 'mythical' control box is?

There are obviously two of them, since rear unit is still working fine.

Anyone? Anyone?

16 Replies

  • You go on the roof. Remove the outside cover. Towards the front of the unit is the grey box with the evaporator coil in it. You remove the 4 nuts and lift off the gray evaporator cover. The control box is right there. That is how it is with our Coleman units.
  • ChaosAgent wrote:
    Ranger Smith wrote:
    The control box is in the duct. You take the cover off then remove the 4 nuts and renove the gray duct . It is in there.


    Hi,

    The only 'ducts' I have is the 2" x 9" one that runs the length of the coach in the ceiling. I have photographed the entire length and can see nothing but empty duct.


    And I also have the duct that comes down out of the AC unit itself. But it comes down directly from the blower motor.

    The control wires come from the side of the opening and lead off in the area between the roof and the ceiling. The 120 vac power also comes from this direction. You can see it here.



    There seems to be no connection with any duct. I have the 15" square opening where the AC unit sits, and the duct connecting the front and back units. That's it.


    You do it from the roof side
  • Ranger Smith wrote:
    The control box is in the duct. You take the cover off then remove the 4 nuts and renove the gray duct . It is in there.


    Hi,

    The only 'ducts' I have is the 2" x 9" one that runs the length of the coach in the ceiling. I have photographed the entire length and can see nothing but empty duct.


    And I also have the duct that comes down out of the AC unit itself. But it comes down directly from the blower motor.

    The control wires come from the side of the opening and lead off in the area between the roof and the ceiling. The 120 vac power also comes from this direction. You can see it here.



    There seems to be no connection with any duct. I have the 15" square opening where the AC unit sits, and the duct connecting the front and back units. That's it.
  • The control box is in the duct. You take the cover off then remove the 4 nuts and renove the gray duct . It is in there.
  • westend wrote:
    By "control box", they may have been inferring the 12V distribution panel in your coach. That would be one of the first areas I would be checking, looking for a bad fuse holder or a partly failed/loose fuse.

    It would be nice if the mfg could tell you how the control box on the non-working AC unit is powered, i.e. the complete circuit. Even if you find a secondary "control box", it must be getting power from somewhere.



    I've checked all the fuses in my 12v panel with no luck. Plus where ever this is, it's got to be in between the thermostat and the unit, since it provides the control signals to the unit. And the fan wires still work.

    Thanks for your help.
  • By "control box", they may have been inferring the 12V distribution panel in your coach. That would be one of the first areas I would be checking, looking for a bad fuse holder or a partly failed/loose fuse.

    It would be nice if the mfg could tell you how the control box on the non-working AC unit is powered, i.e. the complete circuit. Even if you find a secondary "control box", it must be getting power from somewhere.