Mitsubishi MSH-07RV

[airflo]

Hello,

Just had a call from a customer saying his compressor is cutting in and out a lot, his indoor fan seems to running really slow and the fan doesn't change speed when he tries to change the fanspeed via the remote.

Without looking at it i was thinking indoor PCB.

Does everyone agree? or am i missing something?

Sorry i'm new to the service thing :)

Cheers,
airflo

[p_p]

Go to site and have a look for yourself, don't try and fix it before you get there it could be something very simple.


PP

[airflo]

Why would i need to go to site? The site is a 2 hour drive......

The customer is a friend of mine and he has given me all the details over the phone as i have described above. I have dealt with installations of commercial a/c my whole career and i made this post hoping that someone could help a fellow mechanic out and try to pinpoint the problem.

Me going to site is just just going to waste 4 hrs driving to find out i need a part which will mean going back out there a few days later.

Sorry this isn't meant to sound like im having a go at you........i'm just sick of seeing the same post "go to site" when 95% of the details are in the post.

[nike123]

Hello,

Just had a call from a customer saying his compressor is cutting in and out a lot, his indoor fan seems to running really slow and the fan doesn't change speed when he tries to change the fanspeed via the remote.

Without looking at it i was thinking indoor PCB.

Does everyone agree? or am i missing something?

Sorry i'm new to the service thing :)

Cheers,
airflo

As p_p said!
Also, always take what some unqualified person said with big reserve.
For example, from data given you could be only sure in few things:
That voltage supply is present but it may or may not be wrong and that unit is received some command from remote.
All other is disputable.

[rude]

at a guess could be a gas issue. Good chance im wrong tho.

[nike123]

Why would i need to go to site? The site is a 2 hour drive......

The customer is a friend of mine and he has given me all the details over the phone as i have described above. I have dealt with installations of commercial a/c my whole career and i made this post hoping that someone could help a fellow mechanic out and try to pinpoint the problem.

Me going to site is just just going to waste 4 hrs driving to find out i need a part which will mean going back out there a few days later.

Sorry this isn't meant to sound like im having a go at you........i'm just sick of seeing the same post "go to site" when 95% of the details are in the post.

One example:

My boss in previous firm is commercialist and he has some knowledge about split systems from daily contact with me and other technicians. Actually he sometimes give basic advice to some customers about maintenance and simmilar.
One day he told me that his air-conditioner started to losing performance and that is too hot in his apartment. I told him did he check air filter in indoor and that fan is turning. He replied, with chaff, that his wife is cleaned filter recently and that fan is set to high and blowing and that he think that his AC is weak because it is Samsung etc...(we are then dealing with Fujitsus at that time). He was convinced that AC is faulty and already ready to change it with new Fujitsu.

I came to his apartment that afternoon with tools and first thing to do is to check filters.
Of course that they are dirty and that evaporator is iced.
Then after removing them and cleaning them, AC worked as charm. I cleaned Evaporator and fan, and now he curse me, because he has been forced to live with these silly bliiiimp, blouoomp, bluaaamp Samsung audio signals.;)

But if you are sure that you could service by remote viewing and by hearsay, than go ahead!:cool:
Rest of us, without remote viewing capabilities, makes service diagnosis with measuring instruments and our senses at place.


2 Senses (http://en.wikipedia.org/wiki/Sense#Senses)

2.1 Sight (http://en.wikipedia.org/wiki/Sense#Sight)
2.2 Hearing (http://en.wikipedia.org/wiki/Sense#Hearing)
2.3 Taste (http://en.wikipedia.org/wiki/Sense#Taste)
2.4 Smell (http://en.wikipedia.org/wiki/Sense#Smell)
2.5 Touch (http://en.wikipedia.org/wiki/Sense#Touch)
2.6 Balance and acceleration (http://en.wikipedia.org/wiki/Sense#Balance_and_acceleration)
2.7 Temperature (http://en.wikipedia.org/wiki/Sense#Temperature)
2.8 Kinesthetic sense (http://en.wikipedia.org/wiki/Sense#Kinesthetic_sense)
2.9 Pain (http://en.wikipedia.org/wiki/Sense#Pain)
2.10 Other internal senses (http://en.wikipedia.org/wiki/Sense#Other_internal_senses)



That doesn't mean that you cannot take replacement PCB with you.

[p_p]

Why would i need to go to site? The site is a 2 hour drive......

The customer is a friend of mine and he has given me all the details over the phone as i have described above. I have dealt with installations of commercial a/c my whole career and i made this post hoping that someone could help a fellow mechanic out and try to pinpoint the problem.

Me going to site is just just going to waste 4 hrs driving to find out i need a part which will mean going back out there a few days later.

Sorry this isn't meant to sound like im having a go at you........i'm just sick of seeing the same post "go to site" when 95% of the details are in the post.

To make that sort of statement you are obviously very inexperienced, any one worth there salt in this industry knows that there are several components and senarios that can cause the same sympton.
you may take a board with you and it may sort the problem ( very lucky ) what if you get there and its the comp, gas charge, electrical supply, sensor, relay etc, you have purchased a board, travelled 2 hrs and more than likely still not fixed.
As Nike more or less said it is very difficult to remotely diagnose and get it right.
There are alot of excellent engineers on this forum who give good advice.
My advice to you would be to take heed.


PP

[back2space]

Agree with P_P... listen and appreciate the advice your being given on the forum and act on that.

Otherwise what have you come here for? For someone to just agree with your remote diagnosis?

[airflo]

I have come here looking for help as i don't really do any service work and never have since being an apprentice.

I was hoping i could be given some advise on what to look for when i go out there save wasting a trip out there for no reason.

I'm not asking for a remote dignosis i'm asking for your ideas on what it could be so i know what to look for when i'm out there. As i'm not a service tech i don't have a van full of parts and any parts i do need i will have to get from the wholesaler or mitsubishi themselves. If anyone could give me advice or some things i should test whilst im out there this would be a great help.

I know the unit is receiving signals from the remote as the customer gets a beep when he sends a command.

Why would the indoor fan spin slowly at one speed if it was gas problem???

[airflo]

sorry if i sound inexperienced or stupid but i have been on installations since i first started my career and know i have to try and pick all this stuff on my own, so i do the odd jobf for family and friends picking up knowledge along the way.

[rude]

might be blocked filters? that could cause the lack of air flow.

[paul_h]

Possiblitlies:
Blocked filters
Fan full of dirt (the blades get chockas in poorly maintained units, need to remove fan and clean)
Capacitor (fans have small rectangular capacitors 1uF-2uF either loose or soldered to the PCB), the motors don't run very fast without them.
Fan motor fault
PCB fault

[airflo]

Thanks for the replies :D exactky what im after.

Is it possible the capacitor could become faulty over time? or do the just come loose?

How do i pinpoint the fault between PCB and fan motor? I know i can check visually but can i test the motor just like i test any other motor? with a multimeter and megohmeter.

[back2space]

I have come here looking for help as i don't really do any service work and never have since being an apprentice.

I was hoping i could be given some advise on what to look for when i go out there save wasting a trip out there for no reason.

I'm not asking for a remote dignosis i'm asking for your ideas on what it could be so i know what to look for when i'm out there. As i'm not a service tech i don't have a van full of parts and any parts i do need i will have to get from the wholesaler or mitsubishi themselves. If anyone could give me advice or some things i should test whilst im out there this would be a great help.

I know the unit is receiving signals from the remote as the customer gets a beep when he sends a command.

Why would the indoor fan spin slowly at one speed if it was gas problem???

It seemed from your original thread as though you had decided the fault.

And then when advised to go to site you seemed like you didnt want to go to site and asked "why would i need to go to site" this gave us the impression you wanted a remote diagnosis.

[paul_h]

Thanks for the replies :D exactky what im after.

Is it possible the capacitor could become faulty over time? or do the just come loose?

How do i pinpoint the fault between PCB and fan motor? I know i can check visually but can i test the motor just like i test any other motor? with a multimeter and megohmeter.Capacitors just fail over time.
Test the motor and PCB by measuring the windings (you'd need to know what they should be, a sevice manual or a good motor to compare too).
Test the PCB by measuring PCB voltage output on the plug the fan motor connects too, the PCB would be faulty if it wasn't sending out full mains voltage to the motor at high speed setting.

[airflo]

Cool that all makes sense..........how do i go about getting tech data like indoor fan current draw?

Measure the windings with a megOhm meter you mean?


Sorry about all the confusion above i wasn't after a remote diagnosis, sorry if i had given that impression.

[nike123]

Cool that all makes sense..........how do i go about getting tech data like indoor fan current draw?

Measure the windings with a megOhm meter you mean?


Sorry about all the confusion above i wasn't after a remote diagnosis, sorry if i had given that impression.


It is good enough to check voltage at fan connector. If you have correct voltages and correct fan condenser and fan turns happily when turned by hand while AC is disconnected from main supply, than fan motor is faulty.

[Peter_1]

Why would the indoor fan spin slowly at one speed if it was gas problem???

Simply, because an airco with sophisticated electronics in it doesn't react like you're used to see with a normal fridge.
There are a lot of sensors in it, compared with each other and calculated by the PCB which can give a signal to the PCB to give a reaction in a certain way, in a way you normally don't expect.
Possible scenario -not sure if this happens - but machine detects low gas and decreases the fan speed to avoid excessive SH and protect the compressor from overheating.
Does that make sense?

[frank]

Hi Peter

On the Daikin VRV systems I've worked on that appear to be short of gas, the compressor just ramps at low Hz and stays there.
What happens is, at start up, the comp ramps at low Hz and pushes refrigerant around the system. The electronics then look for some feed back from the indoor sensors, indicating a change in temperature across the coil.

If the system is short of gas, the temp change is insufficient and so the comp is not allowed to ramp up to the next stage. Logical really.

[airflo]

True thanks Frank & Peter, that all makes sense.
I just had never seen it slow down the indoor fan, i have worked on quite a few VRV systems and i have actually seen what the compressor does when it short gas.......it just runs really slow and won't pick up speed at all.

Makes sense........