Replacing the fan (impeller) in a Mitsubish Heavy Industires Head unit (model DXK12ZJ-S) after sticking fingers in the blades!

So, like every house husband I was busy cleaning cobwebs from around the house about mid 2014.
The heater was on economy mode in the family room, it's a reverse cycle split aircon system I installed in January 2013.
All was going well until I did what I always preach you should never do - stuck my fingers into the air outlet to clear some cobwebs. One broken finger nail with blood later and a broken fan in the head unit - about 10 blades displaced. My finger was bleeding but not to worry, it would heal. The fan, not so much.
It still worked except from a harsh vibration at anything above the slowest speed. She'll be rite I thought, Ill replace that one day...

That one day was today. The motivation? Well two things, first cracks appearing in the gyprock around the unit as almost a year of vibration has caused it to crack and two, we are now entering a chilly winter and we would like to keep our newborn warm.

Oops...

Good ol' Google. I googled the head unit model number and found the parts and service manuals.  After some digging, I found the part number I needed. I thought, if anything is going to break on a aircon it would most likely be the fan - im sure that I am not the only person who has done as such; and hence, there should be a part available. After more searching, it turns out you can only get parts through the MHI parts dealer in Sydney. Fortunately, my dad is a refrigeration tech so I gave them the part number and other details so his work could order it for me.
A week and $66.70 later it arrived, and today I installed it. One problem - the service manual does not explain how to or the ins and outs of replacing parts. Looks like Ill have to go in alone with just a parts break down to go by...

The first time I installed the fan I did it in-correctly which resulted in a nice tapping sound as the motor was not sitting in its floating bracket properly - which drove my wife nuts. 'It just has to find its home position' I said while hoping it would correct itself - but of course not, as good old murphy would have it, it just got louder and louder... So after putting the kids to bed I stripped the unit apart even further to investigate. My theory was it could only be the motor not sitting properly causing the fan to just touch the chassis. Turns out I was right - this is how you learn. But hey, what do you expect without a service manual? Its a shame Michelle does not see it like this. She sees 'Husband sticks finger in fan, breaks fan, fan costs money, tries to repair it himself and makes worse sound afterwards...' Tapping, buzzing, clicking sounds are my wifes pet hates - I was not getting away with this!


Mitsubishi Heavy Industries DXK12ZJ-S Head Unit

The truth is, I was confident I could replace it - and stop the noise I created. I realise that not everyone knows my experience from working on various things. I have fixed a lot of complex machinery over the years, an air conditioner by comparison, is a breeze.

So, from here on in is the fan replacement procedure - if you are here to know how its done rather than reading my blog. Note that a few times I needed both hands so there are not photos for everything.

YOU WILL NEED: 1 cup coffee beforehand, a number 2 Phillips head screw driver, a little torch to see what you are doing, spray and wipe + cloth to clean all the yellow gunk you will see and some electrical tape to hang stuff (a control board and motor when they will be dangling briefly) OR another set of hands :) and that's all I used... Magnetise your screw driver before hand too, I still have a lost screw behind the TV cabinet...

Ok, so unclip the top cover that covers the filters. If you cannot do this, you should not attempt this, full stop. Oh and now is a good time to turn off power to the unit at the switch board :)

Pull out the filters. On the bottom RHS of the unit there is one visible screw - remove it and unclip the little corner cover.

Now, where the louveres are, on the lower LHS and RHS there is a little plastic thing about 10x10mm - push it up and it will expose a hidden screw (see pic below - covers circled in red)


Screw Locations - unclip by pushing up

After these are out, open the louvres, Carefully and slowly, moving both at same time, about half way open. If they are shut you risk damaging and jamming them against the outer frame. This is more important during re-installation but makes it come off easier too, so just do it.

On the top of the unit there are 3 clips, unclip them and the outer frame will now 'float' (not fall off).
 (see pics below - from LHS to RHS - you can see the clip)


LHS

Centre

RHS

 Now, remove the frame by pulling top towards you and then down, keeping the bottom edge in contact until your at about 45 degrees then pull the frame off - gently.
If it does not come off, there may be some expanda foam holding it there on left hand side. Carefully cut it through the gap using a blunt butter knife.

The drain will probably fall off at the left at this stage - this is ok, just go slowly and gently. Gently pull it out on the right hand side and let it hang from its drain pipe.

You will now have a good view of the fan but are probably wondering.. how the hell do I get that out! This is the part where you need some skill.

Starting on left, remove the screw for the bracket that is attached to the evaporator (metal tubes and fins which by the way - avoid bending). The bracket will now move and can actually move far enough to get the fan out from LHS after unscrewing the other end from the motor - but don't do it this way or the motor will be dislodged from its rubber and foam floating bits inside its housing. This is where I made a mistake the first time! Look, 10 more minutes and you can do this properly so cmon... don't do it the way I know your thinking!

Ok, so now we have to remove the earth straps and sensors on RHS. Here is a photo so you remember how they go. Gently pull the sensors out and DO NOT use metal pliers or you will risk damaging the delicate wires going into the sensors.

Sensor and earth strap locations (click to enlarge)

Now remove the 2 screws holding the control board in place - one right at top and one you can see in the image above (removed) just above the white drain pipe and below the lower earth wire.. see it? Black screw hole.

So now, this can dangle out the way - place it in such a way that there is no stress on the motor wires, let the power wires take the weight of the assembly (it does not weigh much maybe 300g so don't stress too much)

So now you have access to both screws mounting the motor assembly to the chassis. Before we do this, rotate the fan and you will notice a blade missing on the RHS. This is so you can loosen the screw that attaches the fan to the motor shaft - unscrew it 6 turns.
Now, go back and unscrew the mount for the motor and you can remove it. I suggest you don't let it dangle, hold it up with some tape or get someone to hold it for a bit. NOW you can remove the fan by gently moving the evaporator and sliding it out on the left. Note the orientation of that black bearing assembly on left.

So there you go - fan out. Put the lightest smear of G11 grease (medium mineral grease) on the metal/metal SLEAVE bearing... Don't get me started how disappointed I was, there should have been a sealed ball bearing here grrrr... so grease it because they have a quarter of the life span of a ball bearing. Infact, every 2 years, grease it again. The grease on mine was already starting to break down.
Installation is reversal of removal procedure. Go easy, go slow, take photos as you go.
And Goodluck! Here is a parts breakdown that is all I used...
Click on it, and all the photos, for more detailed pics. Note it does not show the evaporator but it doesn't really need to.

 The left, Old Impeller... on right, New Impeller.

I thought the price wasn't too bad considering the size and individual blade construction of the impeller fan.
Its not cast, all those blades are glued in place!

MY AIR CONDITIONER SETUP
Ok heres a boring extra I threw in, I have 3 split systems in my home.
I have a MHI 7.1kw system in the front lounge that is WAY overkill for the size of the room. We basically live in a homette with a large family room built on 3 years ago. Our home is not large by any means. It was originally intended as the only one for the entire house, minus family room extension, to survive hot hot summers. Now it is used to quickly cool or heat the house - using boost mode it takes 10 minutes to warm up or cool down the front area of the house.
I have the MHI where I broke the fan blades in the above blog, it is a 3.5kw unit and is properly sized to properly heat and cool our family room and kitchen - the front room by comparison is half the living space of the family room. It does well (when the fan is not broken)...
In the main bedroom we have a 2.5kw Samsung. I dislike this aircon, it was a cheap 6 star energy rating aircon and was only $670. Me and my dad installed it so we saved on installation - which is also why we have 3 split systems, for us it was cheaper and easier to go this way than a central ducted AND we have the added benefit that if an aircon fails, we still have 2 more!

MHI in front room 7.1kw - overkill heating/cooling and I love it!

Happy wife happy life - Wife and baby enjoying a now fixed split system - MHI 3.5kw

Bedroom split - Samsung 2.5k - too noisey for bedroom and
poor thermostat control...