Today's site attendance / win a pint

[The Viking]

So, the background (always important when trouble shooting):

The unit in question is a wall mounted indoor unit on a Mitsubishi City Multi system, 6 months old.

Last week I was called to site because one of the indoor units wasn't heating, when I connected the laptop to it and looked at the readings I found that the return air sensor was reading 10 degrees above my thermometer. As the sensor checked out OK, a new PCB were ordered.

Today one of our other engineers went to site to fit the new board. After a couple of hours he calls me because the unit has gone in to Error mode after the new board was fitted. The error code was 2503 = drain sensor fault. At this point those of you familiar with these units will think "this is simple, the pratt forgot the link", correctly so as this code should not flag up on a wall mount, only on cassettes. But no, the link were in place.

About an hour after I arrived at site I had to admit that the new board supplied by Mitsu were faulty as well.

Ok, not a big deal, there are other wall mounted units of the same size on site, so we started the "swapping boards" game. And, hey presto, with a working board (as we checked before we swapped we knew the board were OK) everything checks out all right.

Well, apart from one minor inconvenience, the unit still doesn't Bl**dy heat.

And as we have the benefit of the laptop I also start casting my eyes on the unit next door because those readings doesn't look right either (both units are in heating mode, with one unit in cooling/one in heating the problem gets even worse).

Full system tests, a lot of bad thoughts (and language) and several hours later, I finally found the fault.

The first one who correctly guess the fault will receive a pint at the RAC07 or if not attending the show, can claim it whenever we meet.
(I would say that if you get it wrong you have to buy me a pint but I can't drink that many)

[adams?]

controller wired to wrong unit? had that a while back, simple install fault, took hours to find!

[monkey spanners]

pipework crossed?

[The Viking]

Nope, sorry.
(If it were that simple do you think I would offer a pint?)

[Suffolk Fridge]

Faulty solenoid/head in the bc box? Had that a few months back, it sent pressures and temps haywire!

[Andy]

So, the background (always important when trouble shooting):

The unit in question is a wall mounted indoor unit on a Mitsubishi City Multi system, 6 months old.

Last week I was called to site because one of the indoor units wasn't heating, when I connected the laptop to it and looked at the readings I found that the return air sensor was reading 10 degrees above my thermometer. As the sensor checked out OK, a new PCB were ordered.

Today one of our other engineers went to site to fit the new board. After a couple of hours he calls me because the unit has gone in to Error mode after the new board was fitted. The error code was 2503 = drain sensor fault. At this point those of you familiar with these units will think "this is simple, the pratt forgot the link", correctly so as this code should not flag up on a wall mount, only on cassettes. But no, the link were in place.

About an hour after I arrived at site I had to admit that the new board supplied by Mitsu were faulty as well.

Ok, not a big deal, there are other wall mounted units of the same size on site, so we started the "swapping boards" game. And, hey presto, with a working board (as we checked before we swapped we knew the board were OK) everything checks out all right.

Well, apart from one minor inconvenience, the unit still doesn't Bl**dy heat.

And as we have the benefit of the laptop I also start casting my eyes on the unit next door because those readings doesn't look right either (both units are in heating mode, with one unit in cooling/one in heating the problem gets even worse).

Full system tests, a lot of bad thoughts (and language) and several hours later, I finally found the fault.

The first one who correctly guess the fault will receive a pint at the RAC07 or if not attending the show, can claim it whenever we meet.
(I would say that if you get it wrong you have to buy me a pint but I can't drink that many)

Hi Viking

two different sizes of systems, with the indoors mixed up.

Kind Regards Andy

[knight rider]

hi mr viking is the system a city multi r2 system if so , were the port setting on the pcb set in correct ?

[The Viking]

All good guesses, you are now at the point where I were around 4pm.

[a1onetimeagain]

Fan motor running in reverse?

[NoNickName]

I have no idea, but I'm laughing in the face of those installing splits in server rooms (not this case, however).

[Josip]

Hi,

I have no idea................

Me too, but have nothing against to drink that beer with winner

Best regards, Josip

[LRAC]

Nope, sorry.
(If it were that simple do you think I would offer a pint?)

As my kids say "am i bothered" considering you've fixed it.

You must be an old fashioned engineer who never passes on information to help other people out unless its for financial reward, shame on you!

And before you shout back and ask for my opinion on the fault " am i bothered" no i'm not but others will be.

Regards
Lrac

[The Viking]

As my kids say "am i bothered" considering you've fixed it.

You must be an old fashioned engineer who never passes on information to help other people out unless its for financial reward, shame on you!

And before you shout back and ask for my opinion on the fault " am i bothered" no i'm not but others will be.

Regards
Lrac

Sorry Lrac,
You lost me already, exactly what are my "financial gain" here?

I'm the one who offers to buy a pint.
So in my book that's a net loss for me.

The idea behind this post was:
1. To get the less experienced people on this list to use their brains to see if they could crack it (as I, maybe wrongly, assumed that not everybody on this list has yet completed their apprenticeship and/or work practice).
2. To get an idea of just how common this fault was.

And I guess that by posting about strange/odd/unusual problems here I would give the more experienced engineers here another thing to look out for.

My apologies if I upset anyone, I am a newbie here and might (unintentionally) have broken some (unwritten) ethical rule (perhaps by offering to buy another member a pint?).

[marc5180]

Does that mean you arent going to tell us the answer then?

[US Iceman]

The idea behind this post was:
1. To get the less experienced people on this list to use their brains to see if they could crack it (as I, maybe wrongly, assumed that not everybody on this list has yet completed their apprenticeship and/or work practice).
2. To get an idea of just how common this fault was.

And I guess that by posting about strange/odd/unusual problems here I would give the more experienced engineers here another thing to look out for.

All valid points with no bad intentions I see.

Everyone always wants the answers fast don't they?

[chillin out]

Was it a simple fault in the end?

How long did the repair job take?

They weren't piped in series were they?

Chillin

[taz24]

My apologies if I upset anyone, I am a newbie here and might (unintentionally) have broken some (unwritten) ethical rule (perhaps by offering to buy another member a pint?).

I can't see owt wrong in your post.
I quite liked it acctualy.
As for people insisting on the answers,
in my oppinion they have missed the point of the post.
I see it as a little quiz where a senario is posted then clues to the final answers are reveled slowly.

Guys be more patient the Norsman will reveal all in good time.

taz.

[The Viking]

Since the suggestions seems to have stopped.




Here is what I eventually found (after going through most of the suggestions mentioned earlier in the thread).


Checking the output from the BC box's PCB, everything looks OK. The indoor unit connected to "Port 11" energise PCB socket 11 when called for (and vice versa with unit 10).
And if you know the system you know that the plugs that plug in to the PCB, as well as the sockets are colour-coded.
BUT,
When "socket" 11 is energised for heating, the pipes on port 10 gets hot!!!

Solution?
Swap the yellow and the green plugs over and both units are running sweet.

Somewhere in the wiring loom Mitsubishi has crossed the wires or put the solenoid coils on the wrong set of valves!
(By the time I found this it were too late in the day for me to investigate further as to which of these options it really were)


So,
Now I'm off to kick some ###dy installation engineer's #rse for not commissioning properly!
(And to instigate an invoice to Mitsu for the time spent finding their manufacturing fault for them)

[chillin out]

Hi

Found a fault on new system Mitsubishi MS-GA50VB
in a server room.One of the terminals was simply missing
as the 12 V and 240 V have a common terminal(the neutral) the terminal pin for the 12 V the + was missing.
Basically when you look a the terminals coming from the manifacturer you are suposed to see three of them not two.The 12 V cable coming from the PCB was connected to the 240 V one. If power was supplied the pcb should have been cooked nicely.Oh Mitsi i still love you ....:

Somebody done that in the last place I worked and destroyed a few grands worth of kit. I think they blamed it on a faulty pcb....lol

Chillin