Building a Micro-Split AC System


Well-known member
The workmanship skill and thought process as always is impressive. I just don't get how one drive on a silty or muddy road doesn't ruin this thing though.


Engineer In Residence
The workmanship skill and thought process as always is impressive. I just don't get how one drive on a silty or muddy road doesn't ruin this thing though.

So, the AC unit itself is going to be mostly behind my underfloor battery box. Some protection there. Big mudflaps help too. With the condenser facing rearwards, It should stay somewhat clean.

But your right, it could last one year and need reworked. Such is the way with prototypes. On a previous underbody install, what ended up being the problem wasn't mud or dust. It was submersion in water during high crossings. Most automotive fans are fine with getting wet, however they have small gaps. During a water crossing, especially if you are moving quicker than you should, the axle and wheels stir up rocks and sand (pea sized or maybe marble sized) in their wake. The water carries them into the fan housings. Hence why I spent some time sealing the fan casing and bearing caps.

The final protection step, is going to be a vinyl cover. I plan to make one with 3/8" snaps. So I can slide it up and over when needed, and snap into place. Say for the winter, or if I plan to go mud slogging.

Since I used the low loss disconnects, I can drop the unit in about 20 minutes. If the fan motor or condenser kicks the bucket, I can drop and replace with a spare. My plan is too pick up one of these units used for spare parts later this year. They typically start showing up on craigslist at the end of September.

I know lots of folks like to go all-in on reliability, and for safety stuff, I tend to do the same. For comfort items, I tend to lean towards run it till it breaks, then repair and upgrade as needed. Perfect can be the enemy of good. Or in this case, the cool.


Engineer In Residence
Quick update while I am waiting for the unit to stabilize. I charged about 11oz of R410A. Though I vapor charged (intentionally) to get more of the R32 out of the mix. R410 is a 50/50 mix of R32 and R125. I wish I could have run the unit previously to see what the superheat was. Anyways, I am seeing about 125psi on the low side, and around 460psi on the high side. Adding any more refrigerant pushed the power consumption up over 600W. The superheat is something like 18-22 degrees, which seems a bit excessive. This capillary tube was designed for R32, so it may be a little small for 410A? I would need to compare the viscosity to know for sure.

Anyways, It seems to be working fine now. Evap inlet is 85 degrees and outlet is around 61 degrees, which seems like a reasonable detla. I lost a bit of refrigerant when I removed the highs side, as the shrader valve didn't seal. Crap valve...

Recommended books for Overlanding


Engineer In Residence
Started the AC unit at 8:30 this morning. Its been a bit over 8 hours. Total energy consumption is around 3.8kw-hr. The van has been in full sun since 9:30. Its currently 90F and 35% humidity. Its not cold in the van, but its stayed below 85F, and the humidity is low. So its comfortable inside, which is all I really need.


Looks good man. I have the same AC

I considered such an in stall in my camper, but simply dont trust the AC unit that much.
So I opted to keep the AC "stock" to make swapping it out quick and easy.


New member
Great project. I was thinking of doing something similar and I think the 8k BTU Midea U "semi-mini-split" would be a great starting point and pretty efficient with variable speed compressor and fans as others pointed out. This guy takes one apart.



I know zero about ac service, but if I took something like the midea u and cut it inhalf and installed it, would an ac guy be able to add the right charge? What if I lengthened the lines?


Engineer In Residence
Assuming you installed the lines properly, and added a service port, yes. You would need to add extra refrigerant for the lines. It's just a matter of line length and diameter. All these units have a sticker with the charge weight on them.