Figured I'd document how easy it was to upgrade the AC Unit from the old Coleman Mach to one of the Houghton units from Recpro (a worthwhile upgrade IMO since it is both more efficient/less power hungry and quieter). The instructions are...mostly good. Maybe some of my experience on this will help someone in the places it isn't.
As a note, the hardest part was getting it up onto the roof. If you can do basic household wiring (light switches or replacing a light fixture), you can do this yourself (though extra hands for lifting and holding things is always helpful).
Onto the process:
Taking off the old AC unit required taking off the air filters to access 4 screws and then popping the press-fit knobs off. You can see where the screw holes are on the backside with this picture.
I put the knobs back on the unit afterward to prevent myself from losing them and the screws in a ziplock bag. This is the view once it's off and you can see 4 more screws...
...but don't be fooled, once those are off, you have three more in the output tube
It was at this point, I remembered (seeing the wires there) that I should turn off the breaker to make sure I don't electrocute myself. On the breaker panel, mine says it was the second breaker down.
Once you have the unit down, I noticed two things. First, there's a TON of excess wire between the lights fore and aft (toward the front and rear of the unit around the AC unit). It's enough wire to get in your way so be mindful as you move around not to get tangled up in it.
Second, that everything goes through the control unit in the box...the yellow romex caries the power from the RV (just like a house) so loosen those screws holding it in but don't pull it out yet. Just disconnect the control wiring (in the netting on the left of the picture).
At this point, you'll need to move to the underside of the dangling control plate and open up the triangle side of the box (the rectangular side side doesn't need to be opened, thankfully).
From there, you'll see the wago clips holding the wires (does the same job as wire nuts but more compact and easier to work with)...there's three (white = hot, black = neutral, green/bare copper = ground). Undo the wago clips and set them aside, you'll use them again when you reinstall the new one. Straighten out the wires that go to the romex and pull it out (you did loosen the clamp up top, right?).
With the romex pulled out, the control box is unplugged and you should be able to lower down and set aside this piece of interior equipment for the old AC unit, leaving you with a hole and dangling wires. You can also see the last 4 bolts that hold your rooftop AC unit to your roof.
In case you're wondering what size you'll want for these...it's 5/16ths. They are long bolts and it took a bit to get them fully undone, even with a cordless screwdriver. I definitely recommend one for this task rather than doing it by hand. Save your wrists!
If you want to split this whole task into two phases, this is the last stopping point before you have an open hole in your roof. With the bolts undone and the inner clamp dropped out, the only thing holding your AC to your roof is it's weight and a tiny bit of stickyness from the foam gasket on the unit on top. I was able to push it up from inside a little and it popped right loose.
If you haven't lifted your new AC unit (in the box) to the top of the RV before now, this is the time you have to have it done by. I used the packaging of the new unit to set the old unit into and lined up the 4. holes underneath to center it as best as I could (make sure all four holes are visible and easy to line up the included bolts to from underneath...it helps to have two people here, one inside to check the holes and one up top to adjust the unit's positioning). My houghton 15k unit came with the gasket pre-applied to the rooftop AC unit (my parents low profile unit has it separate).
Install the expandable cool air ducting according to the instructions (don't worry, it only fits on one way and has guide plugs). I got excited and forgot to take pictures here but it's really straight forward, I promise. You'll want the shorter screws...the longer screws in the package are for a later step).
Once you have it lined up, you can put the wago clips on the wires and connect up the romex, tying up any excess to keep it out of the way.
Unlike the old unit, all the wiring will just be hanging out in the intake side of the ducting, so just tuck it up out of the way as best as you can. Speaking of tying wires up out of the way...
Get the excess lighting wires out of the way too.
There's one more black plastic piece I forgot to take a picture of, but it connects to the flexible ducting you see in the pictures above and is the interior piece to clamp your roof between it and the 4 bolts to attach it to the rooftop AC unit. The specs for tightening the bolts to are pretty light...I admit I went a little beyond it but the roof did not show any signs of stress or collapse or anything and I've had no leaks after some wet driving and winter camping.
From there, it's just a matter of plugging in the 4 pin connector, snapping the cover in place and screwing the white cover both into the black plastic piece with the longer screws (the visible holes below) and into the roof itself with self tapping screws (those holes are under the intake vents/air filters).
Flip on the breaker and it should power up. Get some batteries into the remote though as that's the only way to adjust it. The touch interface is set to some kindof wonky (in my opinion) settings so I'll never use it.
For comparison, the old unit on the roof (an earlier picture):
And the new unit (snapped before we finished adjustments).
Definitely a recommended upgrade...the old Coleman mach unit was noisy and made it hard to have conversations at the dinette. The new unit is a heat pump so it also provides heat more quietly than the propane furnace. The last benefit is one I've measured over the last few days and it uses half the power of the space heater we were using to keep the inside warm, despite outside temperatures being colder. This is a 20A house plug circuit that only has the RV on it, marked when I installed the unit.
Assuming the cooling mode uses around the same amount of power as the heating mode (since it's just running the compressor in reverse), the power usage is about 1200w when running, down from the 1500-1600w usage I measured on the old coleman during the summer.
