In this article, I show you how to troubleshoot a MR COOL DIY mini split not blowing cold air.

Tools I Used

This post contains affiliate links for which I may make a small commission at no extra cost to you should you make a purchase. See my disclosure page for info on affiliate programs.



Video Tutorial

There are several things which are difficult to fully explain with words and images, so be sure to check out the video tutorial below.



First, I installed a MRCOOL DIY Ductless Mini Split (MRCOOL model: DIY-18-HP-230A) in my home office about 10 months ago. 

Also, I installed the same unit in my workshop – view blog post and video here.

These 2 units worked great during the winter and spring.


MRCOOL DIY Mini Split Problems

My DIY mini split stopped blowing cold air in May of 2017, so I notified MRCOOL via email 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.

Consequently, MRCOOL informed me I would need to call a certified HVAC professional and have them check my unit.

How to Install a Ductless Mini Split - Part 2 - Intro


Low Refrigerant

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.  

As a result, he added more refrigerant and my mini split began cooling again.


Second HVAC Service Call

My MRCOOL mini split stopped blowing cold air 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. 

In turn, 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.

So, 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.


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.  

In turn, 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.  

In addition, the unit arrived at my home 2 days later.


Troubleshooting Process

I was definitely irritated I had to pay an HVAC professional to diagnose my MRCOOL ductless mini split issue on two separate occasions.  

Furthermore, my irritation increased 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.  

Essentially, these units are roughly half the cost of the similar units.  

Furthermore, 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.  

Ultimately, the technicians would significantly raise MRCOOL’s operating costs.  

The increased operating cost rolls downhill to the consumer in order for MRCOOL to remain profitable and stay in business.


Traditional Mini Split Cost vs DIY Mini Split Cost

Obviously, balance exists with everything and mini splits are no different.  

First, 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 factory warranty.  Normally, not as comprehensive as the traditional 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.


Remove Mini Split 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.  

First, 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.

How to Install a Ductless Mini Split - Part 2 - 2


Close Refrigerant Valve

First, it is important to close the refrigerant valves with a hex wrench. 

Essentially, this will prevent the refrigerant from escaping when the lines are disconnected in the next step.  

Next, I remove the nut that protected the valves. 

Then, I tightened the top valve and then the bottom valve.

I take pictures when I work on things I am unfamiliar with.  

Ultimately, this helps me remember how to reassemble things.


Prepare Refrigerant Bundle

I’m not a fan of heights, which is ironic considering I am 6’7″ tall.  

First, I had to release the drain hose & cut out the spray foam in order to pull the refrigerant bundle back through.

Furthermore, 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.

How to Install a Ductless Mini Split - Part 2 - 7



Remove Inside Unit from Wall

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

MRCOOL DIY Ductless Mini Split - Remove Plug - 9


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.

MRCOOL DIY Ductless Mini Split - Lift Mini Split - 10



Pull Refrigerant Bundle

First, I slowly pulled the refrigerant bundle through the wall.  

Obviously, this job requires 2 people.


Improve Mini Split Cosmetics

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

FIrst, this DIY ductless mini split is upstairs in my workshop. 

Also, the wall the inside unit is mounted on is not an exterior wall.

Furthermore, my staircase is behind this wall.

As a result, 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

MRCOOL DIY Ductless Mini Split - Toilet Flange - 13


Unbox new Mini Split Wall Unit

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.


Hang New Mini Split Wall Unit

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.  

Then, 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.  

I mounted the new mini split on the existing wall bracket.

Also, I forgot about the drain hose.

In turn, I had to get my cable fish stick, tape the drain hose to the end and push it through to the exterior wall.


Connect Mini Split Refrigerant Lines and Drain Hose

While I was on my ladder to retrieve the drain hose and straighten the refrigerant pipes, I heard a horse behind me. 

So, I turned around and saw a horse at the back of my fence fussing at me.

Moreover, I completely forgot my neighbor has a few horses on their 10 acre property.

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.


Final Mini Split Not Cooling Test

First, I performed a final test on the unit and everything worked well.

My mini split obviously has refrigerant in it because it is cooling.

Also, I’m sure I lost some since the HVAC professional refilled it.  

Ultimately, I plan on calling him back one more time to come check the levels.

MRCOOL DIY Ductless Mini Split - Final Test - 22



Obviously, this was not an ideal situation.  Equipment & electronics fail – it happens.

However, I’m happy with the support from MRCOOL.

MRCOOL fixed the issue and responded to my issue.

Ultimately, that is all anyone 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.  


Get 25% Off DIY Plans

25% off code will be delivered to your Inbox. **Check your Junk Folder**

I won't send you spam. Unsubscribe at any time. Powered by ConvertKit