Saga of the Coleman-Mach Basement AC

[RVThere]

I was away for a few weeks so only started to work on it again yesterday. I was also delayed by a sheet metal fabricator who did not abide by “measure twice, cut once”. The bottom panel went through three iterations before he got it right...


Made a new drip pan from aluminum instead of galvanized which would eventually rust like the old one.



Here I have the components on the new bottom pan and have started to install the new side panels. I also installed the cold air blower and secured it to the bottom pan.


Beginning the front panels by the electrical access.

Will continue to install the panels and check fit before my “non-union” AC guy comes to recharge and leak check. Will probably install the hot air blower next.

[RVThere]

Today was able to install the hot air blower, reinforce some rusted sheet metal, and test fit all of the exterior panels.



I’m in the process of securing the compressor bolts to the bottom panel with cold weld epoxy

[Solo_RV_Guy]

Nice work! Thanks for the update.

[Almost There]

When you’re done it will be better than new.
Fantastic job!

[TheWoodBoss]

I love our basement air. I have worked on many AC units from home to cars. My Dad has his license and all the equipment to service these. When mine gives us a problem we will fix what ever it needs. Having the unit under is real nice and quiet while in the RV. I like the design and not having units on the roof. Looks like you are doing a great job.

[RVThere]

Finally an update as my AC buddy found time to come to the barn to look at my rebuilt basement AC.

He spent some time familiarizing himself with how the coolant pipes were routed and figuring which pipes belonged to which compressor.

As expected, he focused on the circuit that was freezing up. He carefully drilled into the pipes and brazed valves onto the high and low sides.



He commented that not much came out of the pipes but they did have pressure which was a good sign. He put nitrogen in to check for leaks and then applied a vacuum to clean out the system.


Following the specs on the unit label, he added a little more than the 28.25 oz of R-22 Freon and started measuring the pressures and input and exit air temps. Since the temp in the barn was about 60 degrees, we constricted the coil on the hot side to provide a false heat load. COLD air started pouring out of the blower!



He checked the amp draw on the compressors to make sure they were within the specs listed on the compressor housing. He let out some Freon to reduce the head pressure and reduce the amp draw on our problem circuit.

He suspects there is a VERY small leak but the Freon charge should be good for years. With the ports now installed, any future recharge will be simple. He tested the other compressor and circuit and said they were fine.



He only charged me $200 and took about 2 hours.

One word of caution is the self tapping screws I used to secure the sheet metal lid. One nicked the copper pipe but did not cause a leak.



So I will be extra careful when reassembling the covers.

Next step is reinstallation!

[Solo_RV_Guy]

Thanks for the update, Tom. You've done some really nice work!

[Jim_HiTek]

I did my '02 back in April of '19 and wrote an ad free blog article about it here. Mine wasn't nearly as rusted as yours. Very happy I didn't have to deal with the kind of rust you had. What rust I did have, I just wire brushed than treated with Jasco Prep & Primer and let it go at that. Also replaced the main bushings with ball bearings...found them at Granger. Oiled all the motor bushings that couldn't be replaced with mineral oil. Replaced all the motor start and run caps. If you haven't done that, I'd suggest it, I didn't see them mentioned in this tread. In my case, I just had a very noisy operation and that was just due to the bearings and the caps, cooling/heating was and is fine.

I'd add my name to the list of those that love the basement air units. I've had both, and if I ever get a newer RV, it will have basement air if at all possible.

If you removed the rear bumper on your rig, that's where you'll find the way to remove the cover over the hinges for the basement compartments so with removal of a couple screws per hinge they can be removed without removing the rivets on the doors. I just removed the cover and that allowed the door to be fully opened for better access. AND with the bumper removed you have much much better access to the output air ducting elbow and higher up on the ducting to check for or repair leaks. My rear bumper is only held on by 3 screws on either side, and then those epoxy glued on brackets which are usually broken away in older RVs so I added screws to hold the bumper. (It's really not a bumper of course, just a sheet of formed fiberglass).

Anyway, great thread! Thanks for the pictures.

[Almost There]

Excellent work
Thank you for taking the time to document everything, those following will find it much easier to take on this job.
Enjoy the cool!

[RVThere]

My son and I heaved the unit back onto the chassis



They hardest part was lining up the duct to the unit output vent. You need to make microscopic adjustments with a dead blow hammer and a 2x4!



Finally lined it up, rammed some foam tape in the gaps, secured it with some screws, and taped it up.



Should have time on Friday to hook up all the wires and finish it up.

[RVThere]

Inconclusive at the current time.

Hooked up the power yesterday and attempted to run the AC. Looking through my access, the darn pipe is freezing up.



Pump some heat into the coach but no improvement. Leave message with the AC guy.

Come back from lunch and put it on heat pump mode as a test. It works and starts warming the coach.

Switch back to AC and it works too. Pumps cold air with no freeze up



AC guy calls and says that 50 degree ambient temperature is way out of the specs for cooling. No head pressure, no heat load. So I can’t really call it good or bad.

Today I decided to run the AC one more time and the other circuit freezes up! What the heck?



So at that point, I screwed closed the access panel and secured the outside panel. I’m leaving for FL on Christmas so we’ll give it a true test then!

Stay tuned!

[TWT]

Coming in a little late on this; but, I find it very interesting! I will keep following, to see how it all works out. We have a basement heat pump in our '05 Itasca (Winnebago) Horizon. It is much better than the roof A/Cs...


Looks like you've done some fine work.