How to Repair a Ductless Mini Split Air Conditioner

Introduction: How to Repair a Ductless Mini Split Air Conditioner

About: Hi Everyone, I'm Jeremy Hoffpauir. I write instructables about unique DIY woodworking and home improvement projects. I use unique design elements with a rustic coastal style in my creations such as epoxy...

Hey Everyone! Jeremy Hoffpauir here. I installed a MRCOOL DIY Ductless Mini Split in my home office about 10 months ago. I also installed the same unit in my workshop - view blog post and video here. The DIY Ductless Mini Split stopped cooling, so I filed a warranty claim with MRCOOL to replace it.

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Step 1: Background on the Issue

I installed a ductless mini split (MRCOOL model: DIY-18-HP-230A) upstairs in my workshop in October of 2016.  It worked great during the winter and spring. My DIY mini split stopped cooling in May of 2017, so I notified MRCOOL via email and notified them of my problem.  The folks at MRCOOL were very responsive and we traded a few emails regarding troubleshooting tips and results.  Unfortunately, we were not successful in resolving my issue.  MRCOOL informed me I would need to call a certified HVAC professional and have them check my unit.

Low Refrigerant - May 2017

The HVAC professional tested my unit and determined my DIY ductless mini split was low on refrigerant.  After spending roughly 30 minutes checking for a refrigerant leak, he could not find a leak.  The HVAC technician and I came to the conclusion my MRCOOL mini split was not properly pre-charged from the factory.  Or, refrigerant was lost during the installation. Either way, my ductless mini split needed more refrigerant.  He added more refrigerant and my mini split began cooling again.

Low Refrigerant - August 2017

My MRCOOL mini split stopped cooling again in August.  I didn't spend much time in my home office in June and July, so it is quite possible it stopped cooling in June or July.  I did not call MRCOOL for this issue; rather, I called my HVAC professional again. The HVAC professional put his gauges on my mini split and explained my unit was in a 'vacuum'.  This means the unit has no refrigerant whatsoever.  It was obvious now my mini split definitely had a leak.  After he recharged the unit with refrigerant, he spent over an hour taking apart my ductless mini split (outside and inside unit) to locate the leak.  Despite his best efforts, he could not find the leak.  

Step 2: Filing the Warranty Claim

MRCOOL Warranty Claim

I found the original email chain I sent to MRCOOL in May and used it to notify them of my updated issue.  They responded immediately and asked for additional information from the unit.  Once I provided them with the serial numbers, receipt, and a few other items - they shipped a new inside unit and line set.  It arrived at my home 2 days later.

MRCOOL - A Different Perspective

I was definitely irritated I had to pay an HVAC professional to diagnose my MRCOOL ductless mini split issue on two separate occasions.  Especially considering my unit was under warranty and less than a year old. After thinking about the situation from MRCOOL's perspective, I began to understand why it is not feasible for MRCOOL to have technicians spread throughout the country to diagnose warranty issues.  These units are roughly half the cost of the similar units.  It is not possible for MRCOOL to sell their DIY mini splits at such an affordable price and pay technicians throughout the country for maintenance issues.  The technicians would significantly raise MRCOOL's operating costs.  This increased operating cost would be passed to the consumer in order for MRCOOL to remain profitable and stay in business.

Traditional Mini Split vs DIY Mini Split

There is a 'give and take' with just about everything and mini splits are no different.  A conventional DIY mini split costs approximately $3800.00 with a full warranty, which includes diagnosis and troubleshooting.  The MRCOOL DIY Ductless Mini Split of similar size is $1,450.00 with a warranty that is not as comprehensive as the conventional system.  In other words, pick your poison. Now, on to the steps I took to install my mini split I received as a result of my warranty claim.  

Step 3: Remove Covers

The unit on the right is for my home office and the unit on the left is for my workshop - view video and detailed instructions here.  I removed the top cover and disconnected the electrical line that connects to the inside unit.  Next, I removed the bottom cover and placed it to the side.

Step 4: Close Refrigerant Valve

One of the most important steps to this project is to close the refrigerant valves with a hex wrench. This will prevent the refrigerant from escaping when the lines are disconnected in the next step. I remove the nut that protected the valves, I tightened the top valve and then the bottom valve.

I take pictures when I do work on things I am unfamiliar with for future reference.

Step 5: Prepare Refrigerant Bundle

I'm not a fan of heights, which is ironic considering I am 6'7" tall. I had to release the drain hose & cut out the spray foam in order to pull the refrigerant bundle back through.

The drain hose for my MRCOOL DIY Ductless Mini Split was secured to the refrigerant bundle with tie straps. Additionally, I had to cut away the spray foam that sealed the hole for the refrigerant bundle.

It doesn't look high, but it certainly is higher than it looks

Step 6: Remove Inside Unit From Wall

Next, I disconnected the drain hose from the inside unit of my mini split.

Once the drain hose was disconnected, I pulled a bit of slack inside from the refrigerant bundle. Next, I slowly lifted the inside unit from the wall bracket and gently laid it on the ground.

Step 7: Pull Refrigerant Bundle

I slowly pulled the refrigerant bundle through the wall. This was a bit difficult since I was doing this alone. It would have been much easier to do this with two people.

Step 8: The Chance to Improve My Unique Installation

Most mini split installs are very straightforward. However, mine is a bit different and more complex.

This DIY ductless mini split is upstairs in my workshop. The wall the inside unit is mounted on is not an exterior wall. My staircase is behind this wall; therefore, the refrigerant bundle has to pass through this 4 foot space to get to the exterior wall.

Since my home office has a maritime/marine theme, I built a box with a ship bell to hide the 3" PVC pipe that houses the refrigerant bundle.

I also decided to purchase a toilet floor flange (not sure the proper name) to improve the look of the PVC wall plate that comes with the unit. It actually fits nicely with the theme of the room

Step 9: Unbox Mini Split

I unboxed the new MRCOOL DIY Ductless Mini Split. Instead of replacing my remote control mount and reconfiguring my WiFi, I transferred them from my old unit to my new unit.

Step 10: Hang New Mini Split

Next, I pushed the refrigerant bundle through the hole in the wall to the exterior wall as far as I could while the mini split was on the floor. I placed the new DIY ductless mini split on the top of my ladder and strapped it down so it would not fall. Quick Tip: Ask someone to help you because it makes things much easier.

While the mini split was on the ladder, I pushed more refrigerant bundle slack through the wall. Next, I mounted the new mini split on the existing wall bracket.

I completely forgot about the drain hose, so I had to get my cable fish stick, tape the drain hose to the end and push it through to the exterior wall.

Step 11: Connect Refrigerant Lines

While I was on my ladder to retrieve the drain hose and straighten the refrigerant pipes, I heard a horse behind me. I turned around and saw a horse at the back of my fence fussing at me. I completely forgot my neighbor has a few horses on their property, which is about 10 acres.

Next, I reconnected the refrigerant lines to the outdoor condenser unit on my MRCOOL DIY Ductless Mini Split. If you would like to learn how to do this, checkout my post on how to install a DIY Ductless Mini Split.

Step 12: Test the New Unit

I performed a final test on the unit and everything worked well. My mini split obviously has refrigerant in it because it is cooling; however, I'm sure I lost some since the HVAC professional refilled it. I plan on calling him back one more time to come check the levels.

Step 13: Final Thoughts

As I mentioned previously, this was not an ideal situation. However, I'm happy with the support I received from MRCOOL. Equipment & electronics fail - it happens. MRCOOL stood behind their product by replacing it and they were very responsive to my issues. Ultimately, that is all I can ask for.

NOTE: MRCOOL did not pay me nor did they send me anything for free in exchange for this video or blog post. #notsponsored

Be sure to check out my video on how to install a mini split.

I hope this project provided you with some value because this is, and always will be, my ultimate goal.

Please consider subscribing to my YouTube channel and visiting my website for more projects and other fun stuff.

Feel free to contact me anytime if you have any questions.

I'm happy to help! Until next time – Imagine…Create…Share

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    9 Discussions


    Question 1 year ago on Step 13

    hi; good job explaining , I have exactly what you have 2= DIY 18K MRCOOL units. I also have the same issue, except 1 unit not quite as bad still works but seems "iffy" My hope is you can tell me how your TECH checked the unit for lack of freon. There is only the LOW PORT no high port. MRCOOL won't tell a commoner any thing as to how to check. Don't get me wrong I am not a TECH and I DO NOT WANT TO SERVICE THE UNIT all I would like to do is test it (which is legal ) I have the equipment because I do cars, and my gauge set is for R134 and R410. I would like to "know" if I need my TECH here or not. I have tested for leaks and have not found any. Buy the way did you know the LED panel is supposed to tell you if it is leaking..I take it that yours did not ? my is not but I had a little icing and they said it is probably low but I got no code on mine either, which is why I would like to know what psi it should have or temps, etc. what ever you tech looked at to decide it was low,and the second time empty? thanks in advance for any help with this. G


    Answer 1 year ago

    Is icing a sign of low refrigerant?


    Reply 1 year ago

    YES...if in AC mode the inside fins will ice up then it interferes with air flow and starts melting and dripping off the louvers (not nice) if in heat mode the outside fins ice up same thing with the air flow..Sense this .... I found out a couple things. 1= R410 has NO rules that make it illegal to buy and use per the EPA, it is not ozone depleting (still finding someone to sell it is tough) 2= MRCOOL low side requires 135 psi. 3= they sent me the freon FREE and I installed it in the units, and they have been working perfect.


    Reply 1 year ago

    You received Freon from MrCool free? How did you go about testing your unit then installing the refrigerant?


    Question 1 year ago on Introduction

    18,000 btu mrcool minisplit. How do you get the cover off of the inside unit? I need to replace the defrost switch that was furnished by mrcool. I can find only 2 screws on the lower front cover. Don't want to pull too hard and break something.


    1 year ago

    Very useful video. I have a Mr. Cool DIY Mini Split as well, and I'm trying to diagnose a problem. Can you tell me, how did you get the front cover off? It seems like I'm so close to being able to remove it, but there seems to be one screw or something holding it back, maybe in the upper right corner. I found the three screws along the bottom, is there another connection I'm missing? Thanks.


    Question 2 years ago on Step 5

    Can you tell me what is the length of the refrigerant bundle? Thx


    2 years ago

    I'm really impressed as to how the industry has changed. There was once a time when a system had to be purged with nitrogen, thoroughly evacuated down to less than 500 microns, checked for leaks and then properly charged, has the world changed. It's amazing that the manufacturer will actually warranty their product without purging the air, water vapor, and other contaminants that may exist in the lineset. I guess it's time for me to go back to school, another lesson learned.