Mitsubishi Heavy Idustries A/C Stopped

HI,
My 8 yr. old MHI A/C SRK71ZEA-S only gets used about a week every summer for the last 8 yrs, so its not worn out, but today I put it on for the first time this year and after about 2/3 hours it stopped working and flicked the Circuit Breaker Switch off for this unit at the power box and wont start up and the indoor unit RUN light is solid on and the TIMER light flashes 6 times, meaning if I read Self Diagnosis Function page properly says under "Description of Trouble"-(Error of signal transmission) and Cause is- Defective power supply, Broken signal wire, defective in/outdoor unit boards.

So with this problem, does anyone know if there is a common fault problem with this unit, I checked the outside unit fuse and its not blown. So is it the PCB boards burned out or something.

I spent a bit more money back then getting this A/C as thought it would be more reliable and robust than others like my Fujitsu's that are same age and are still running good, so very disappointed.

check your interconnect cable between indoor/outdoor no3 wire should be a pulsed 24v dc- if its a fixed output then possibly indoor pcb, check leds on outdoor pcb, also check for gecko's, snakes,bugs

Thanks for your reply IM,
I pulled the top/side covers off this arvo after it stopped and PCB looked all clean, and no dead insect bodies, but had a burnt smell and thought something must have got hot and burnt out and shorted out, as it flicked the circuit breaker for this unit at power box, so that's not good, so flicked breaker back on and it didn't cut out, but when I usually turn this outside unit on, I've always heard it click on inside, but now it doesn't, so the outside unit isn't excepting any mains power into it and the fan motor still turns around and there's still power at the inside unit and where do I check outside LED's, as I know with my other A/C, a Daikin, I just had to take the long end cover off to see the LED's up the top, but this MHI hasn't got them there.
When my old Daikin PCB's failed a 3 years ago, it didn't shut the circuit breaker off and it didn't have any burnt smell either and just put some new PCB's and works good.
So with the burnt smell and it shut the circuit breaker, I'm thinking this MHI has gone out in a big way.
Thanks

http://210.1.42.215/tech_info/Manual...3,71ZEA-S1.pdf
service /parts list-

looks like outdoor pcb issues- theres 2 of them 1 power pcb and 1 main pcb- had it on 1 yrs ago where a resistor went pop on the powerboard and shorted the main pcb so had to replace both outdoor pcbs

Thanks IM,Yes that's what I think as well-outside PCB's, probably not worth fixing, do you know how much these outside PCB's are, why would they fail though, bad quality or something or could of a power surge done it, it was a hot day here in Brisbane, so don't know if a power surge could happen.Thanks

check for power to the fuse in the outdoor unit- on the main pcb theres an led, see if its lit or pulsing, power pcb only runs the compressor so if its comms issue then prob main pcb- the 1 with the led on it,
pcbs can be repaired there are electronics companies that will test pcbs

How much are these PCB's.

http://www.mrespareparts.com.au/About.html
might have to via a techie company to get prices
https://www.mhiaa.com.au/index.php

I took the top PCB off unit and had a look underneath and the other 2 PCB all over and cant find anything blown or burnt out and all these PCB's were clean with no signs of geckos etc. So what would make it fail.

I cant find that LED your talking about, is there a photo at all indicating where it is, I also checked the fan motor, took fan blade off and unplugged it and gave it a flick and it turns the 1,1/2 - 2 turns OK.

I worked out over the 8/9 yrs I've had this aircon, used only about a week at summer yearly, if that, its got a total off just over 2 months of use, so not worn out at all.

This unit failing prematurely has turned me off on this "Mitsubishi Heavy Industries" what does the "Heavy" word mean, not heavy duty parts by the looks, a bit misleading.

OK,

Something blew the powersupply but there is no visable burnmarks on the PCBs...
Not many parts that would be able to do that without burning themselves.
Before you go too far down the route of replacing the PCBs, do check the compressor and outdoor fan for electrical soundness.

By the look of things, it is time to call an engineer out and get his (her?) verdict on the system.

:cool:

Thanks Vik, the outdoor fan is good, I checked that, how do I check compressor, when I used to turn the power switch on outside the unit, it made a quick buzzing sound and then went off that they all should do by the sounds, but this one doesn't do it now when turning on switch, there's still power going to inside unit though, have you come across this problem before.

Quote:

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Originally Posted by install monkey

http://210.1.42.215/tech_info/Manual...3,71ZEA-S1.pdf
service /parts list-

looks like outdoor pcb issues- theres 2 of them 1 power pcb and 1 main pcb- had it on 1 yrs ago where a resistor went pop on the powerboard and shorted the main pcb so had to replace both outdoor pcbs

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When the resistor went pop on powerboard, did the resiter have signs that it was damaged/blown/burnt and did it flick the power box circuit breaker like it did with mine.

didnt spot the charred resistor till i removed the top pcb to expose the lump of metal on the adjacent board

Thanks IM, so what causes these parts to fail like that. Have you have any that's flicked the circuit breaker.

I rang up MHI Tech Support here in Australia yesterday and they said there aircon units are bullet proof and I asked about the "Heavy" word in there name and I said does it mean all parts are Heavy duty and he said yes and he said mine shouldn't have failed for the little time its been used and he said other things might be the problem like the corrosion(couldn't see any)cable could be eating by rodents,(I checked the roof and all good).

And I said all components on the 3 PCB's haven't blown up or burnt,(unless its internal and didn't expand out), its weird that it flicked the circuit breaker, you would think some component shorted out that flicked circuit breaker off, if that did happen, you would think the component that failed would of blown up like your resistor.

I'll check what you said earlier about No.3 wire 24v DC on the inside unit, so is it still 24v DC on these Australian 250v systems, are yours the same, I'll also check to make sure the main power switch on outside unit is OK.

HI Install Monkey, Is there a PCB and compressor test procedure Manual for these MHI that some one could send me.
We checked the mains voltage, and there's 248 volt out of main outside unit switch, back out and into lead to inside unit and inside unit, so just need to check the PCB and compressor if possible and fans all good.

The lights that indicating error codes aren't blinking inside anymore, the inside unit responds to all remote control commands, but outside units still not doing anything and still cant find that LED light you said on outside unit, the Daikin's have a good LED light setup on the outside unit, but these MHI aren't the same. Thanks

page 65,66 on that link i posted shows inverter pcb test procedure and test points on the pcb

Quote:

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Originally Posted by install monkey

check your interconnect cable between indoor/outdoor no3 wire should be a pulsed 24v dc- if its a fixed output then possibly indoor pcb, check leds on outdoor pcb, also check for gecko's, snakes,bugs

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HI IM, I checked what you said above and as it says procedure (Error of signal transmission) in manual Page 60 between wires No.3 and no.2 wire on inside unit and with unit ON and fan on it pulses at 13.90-16.53 DC volts and with inside unit turned off, its stationary at 0.04v DC, and the outside No.2-3 are the same, so what's that saying. Thanks

under normal conditions 2,3 should be a pulsed signal, if you disconnect wire no3 leaving the outdoor then on terminal 3 on the outdoor you would have a fixed 24v dc approx output from the outdoor connection, the pulsed signal your getting is correct, you say the indoor fan,louvre starts so possibly outdoor pcb isnt asking for the comp to start up and the lev's to chatter when powered up,
page 66 shows where you should have power on the outdoor pcb, and the led labelled RL

Thanks IM, I was just looking through manual again as you sent message, on page 66, its got about (6.2) Servicing-Evacuation of unit with gas. Thanks

Quote:

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Originally Posted by sjbrewy

Thanks IM, I was just looking through manual again as you sent message, on page 66, its got about (6.2) Servicing-Evacuation of unit with gas. Thanks

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Maybe its page 64 is it.

actual page 64 on the manual, it counts the front page as page 1:confused:

That diagram is just the top main bigger PCB, so there's no checks diagram for the other 2 smaller PCB's.

Quote:

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Originally Posted by install monkey

actual page 64 on the manual, it counts the front page as page 1:confused:

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I see what's happened about the page numbering, Adobe reader counter on top of screen is saying its 2 pages more, but the page number on Tech Manual page is 2 pages less, so Adobe reader is messing our heads up.
So you were looking at the adobe counter page numbers and I was looking at the manual page numbers, so all sorted now, we're on the same page. Thanks

Quote:

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Originally Posted by install monkey

check for power to the fuse in the outdoor unit- on the main pcb theres an led, see if its lit or pulsing, power pcb only runs the compressor so if its comms issue then prob main pcb- the 1 with the led on it,
pcbs can be repaired there are electronics companies that will test pcbs

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HI IM, Reagrding the LED that suppose to be on the main PCB, what if there's none on there, have I got a dodgy PCB, I was going to send you a photo of this main board, but cant see an option to do that.

click on my profile and then about me- download vcard, my e mail address is on there;)

HI, Could someone please tell me how to check this MHI SRC71ZEA-S compressor to see if inside is OK with a Digital Multimeter, there's 3 wires, a dark grey, white, pink wire on top of compressor and what Ohms numbering setting on multimeter do I use, there's Ohms 2M,200K,20K,2K,200. Thanks

You need an Insulation Tester to check if the compressor is OK http://www.fluke.com/fluke/uken/prod...on-Testers.htm

HI IM, I checked all 3 tri connecters on top of compressor just incase and came up 01.1 ohms each tri connection, so equals 02.2ohms, so that's good then is it and can the outside PCB's still be checked if power inverter PCB is gone, as it sounds like this power inverter PCB is gone, if so how is it checked, as I mentioned earlier there's nothing blown on these PCB's. Thanks

Windings ohm readings on compressor are too low. Compressor motor failed.
Power = voltage squared divided by resistance. 3phase compressor at 2.2 ohms= 72 Kws., single phase = 24 Kws drawn power.
Probably what you do not what the here, the inrush current trip supply CB, as well destroy the contactor starting compressor, hence the smell of something burnt.

OK Thanks Magoo, What readings should I be if it was a good compressor.
Are all these aircons made the same, as I tested my other aircon that's a Daikin same size and that's working fine to compare compressor ohms with as I wasn't sure if I was doing it right and it gave me a reading of 1.0 and 1.1 and I tested these with just a Digital Multimeter set on ohms setting of 200. Some one said it should be tested with a Insulation tester. Thanks

This might help you..http://www.fluke.com/fluke/uses/comu...ation+test.htm

inverter compressors have resistances of typically 1/2 of a non inverter pot- so 1.1 ohm accross any 2 pins is ok,- based on 230v 50htz supply, this test can be performed with a standard digital or analogue multi meter with the compressor leads removed after the inverter circuit has discharged- 2 mins after powering down
insulation test is performed using a megohm meter- (meggar) set at 500v and connect black lead to the compressor body- disconnect the cables on the terminals and and connect to a pin- press the zappy button and over 1 meg ohm is ok, repeat for the other 2 pins

Quote:

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Originally Posted by install monkey

inverter compressors have resistances of typically 1/2 of a non inverter pot- so 1.1 ohm accross any 2 pins is ok,- based on 230v 50htz supply, this test can be performed with a standard digital or analogue multi meter with the compressor leads removed after the inverter circuit has discharged- 2 mins after powering down
insulation test is performed using a megohm meter- (meggar) set at 500v and connect black lead to the compressor body- disconnect the cables on the terminals and and connect to a pin- press the zappy button and over 1 meg ohm is ok, repeat for the other 2 pins

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OK Thanks IM, so compressors OK, that's good as its hardly been used, still looks brand new, so it comes down to the Outside Power Inverter PCB being at fault by the sounds, as outside unit doesn't do anything, no sounds when turned on, as it use to, can this PCB and others still be tested if power inverter PCB has failed, as it powers the others, as I heard this, and do these power inverter pcb fail like this for no apparent reason.

https://drive.google.com/file/d/0Bz6...ew?usp=sharing
courtesy of tayters

Thanks IM,

Quote:

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Originally Posted by install monkey

https://drive.google.com/file/d/0Bz6...ew?usp=sharing
courtesy of tayters

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I checked the P and N terminals on the inverter PCB and there's no power there at all, as with the U,V,W checks, so it sounds like this PCB is stuffed. I see at the Power Source that the N and L wires goes to the Main PCB from the mains house power supply in, so does the power go through this Main PCB before it goes to the Inverter PCB, is there any checks on the Main PCB I can do and the Capacitor PCB if possible. What does it mean with these outside PCB if I'm still getting full power and good operational commands with the inside unit, does it mean that the outside main PCB is still good.