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Taaz1275
11-12-2012, 11:33 AM
Hi
This is a split unit,cassette and going thru intermittent trip with error code E57, which indicates shortage of refrigerant or closed service valve. Can someone please point out where my problem is.
I have replaced the the PCB with all thermistors in the indoor unit, have recovered system gas(R410) and recharged unit thru designed recommended weight, but unit is still tripping intermittently with E57 error code on wired remote controller.

Stressing out on this one, and therefore any assistance will be greatly appreciated.

Andy AC
11-12-2012, 11:02 PM
I had a problem on a mhi 12kw inverter system a while ago that refused to start, turned out to be faulty pressure/temp transducer on outdoor unit, apparently not uncommon, it wasn't registering anything so stopped the unit from running. When you have the system running, check the lp running pressures on the controller and compare it with you gauge readings to see if it is wildly out, or if it has a reading at all.
It looks like a normal pressure switch, but these ones are actually screwed on to a 1/4 inch flare buried in a very awkward to get to place, usually in behind the flare connections. Depending on series of the outdoor unit, it could be at low level at the bottom right hand side of the machine. Beware - there is no schrader core behind it:mad:, so if you have to change it, it will be a recovery job first:(. I found out the painful way:o

Taaz1275
12-12-2012, 04:58 AM
@ Andy AC,thanks a lot for that insight, I haven't attended to the unit yet but will do soon and definately I will look into that point.
Unit Details: Outdoor Model unit: FDCVA251HEN Indoor Model unit:FDTA251
Will inform everyone on the outcome of this problem once a solution is achieved,....but will still accept any ideas from the forum as problem still exist.

ozairman
14-12-2012, 03:00 PM
Hi
This is a split unit,cassette and going thru intermittent trip with error code E57, which indicates shortage of refrigerant or closed service valve. Can someone please point out where my problem is.
I have replaced the the PCB with all thermistors in the indoor unit, have recovered system gas(R410) and recharged unit thru designed recommended weight, but unit is still tripping intermittently with E57 error code on wired remote controller.

Stressing out on this one, and therefore any assistance will be greatly appreciated.

E57 is triggered by an insufficient change between the Indoor pipe temp sensor Thi-R1 and the Indoor room temp sensor Thi-A once the unit has started cooling or heating. In cooling/dry mode it is looking for at least 4 degrees drop in temp after 1 minute operation and in heating at least 4 degrees rise after 9 minutes operation.

If you have changed the PCB and sensors, have you made sure that the sensors are in the right positions and that the new PCB was set to the same as the old one? A quick way to check the Indoor sensor resistances is to run the unit in fan only for 10 minutes then measure the resistance of all the sensors, they should be about the same resistance as all MHI indoor sensors are 5KΩ @ 25C.

You are in luck with the wired remote controller, once you start the system to test it press the Check Button at the bottom of the remote and select Operation Data and press the Set button. When the data loads you can use the Timer up down arrows to monitor the operation of the unit. Look closely at the Indoor sensors, Return Air = Thi-A, I/U Heat Exch 1= Thi-R1 and I/U Heat Exch 2 = Thi-R2 to see what is going on.

Taaz1275
16-12-2012, 09:55 AM
@ ozairman,I am putting all these important points onboard, I will soon be getting back to that fault very soon and by then I should be able to post back the results.
Thanks a lot for that insight as well, very much appreciated as I myself was not getting anywhere as Im not that too familiar with MHI units, if not for the service manual I would be totally lost.

Taaz1275
08-01-2013, 05:57 AM
Hi Ozairman,
Today i managed to get back to this unit, and with all the insights given to me by you and Andy AC, tried once more to tackle this issue.
For you guys info, on this site there are 3 of this units of this same model, each unit is on its own with is own controller, the units have been there for more than 5 years and running fine till nowadays.
Anyway, did checks on controller while unit is operating on cool mode and found thermister readings on controller to be slightly higher then air off temperature as measured with a digital thermometer.
This was the same for all 3 units which are all going thru the same fault.
Redo checks on thermister readings on unit where indoor control pcb plus all thermisters were replaced, and found thermister temperature readings on controller to be way higher(warmer) then air off coil temperature.
I have contacted the Mitsi local tech assistance who finds it strange, but anyway, I have ordered all thermisters for each unit to be replaced before I can continue with the assessment of this fault once more.
Just another question for you Ozairman thats if you dont mind, do you have any idea of how to erase the fault history on the wired remote controller so just that I can start off from nothing....and work my way from there as starting point.
appreciate all the advice and assistance...thanks guys...will keep you guys posted on the outcome of this one...cheers!

Taaz1275
25-01-2013, 08:53 AM
Update on this fault, Ozairman's point has been really helpful, all indoor thermisters for the 3 units has been replaced and the refrigerant charge in the system is correct, going thru the procedure as Ozairman mentioned...found that the thermisters were faulty reason for them being replaced.
The check button and and the Operation Data check as Ozairman mentioned did really help...what happened is that I ended up replacing the EEV with the coil because the 4 degrees drop within 1 minute was too slow, but not after replacing the EEV & coil...bear in mind that the thermisters that were replaced were proven to be faulty in relation to its resistance test and temperature reading as seen on the remote controller.
Things looking brighter and life more relaxed, thanks Ozairman & Andy AC for making life much more fun for me now....appreciate the help...thanx guys.

ozairman
29-01-2013, 01:47 PM
Update on this fault, Ozairman's point has been really helpful, all indoor thermisters for the 3 units has been replaced and the refrigerant charge in the system is correct, going thru the procedure as Ozairman mentioned...found that the thermisters were faulty reason for them being replaced.
The check button and and the Operation Data check as Ozairman mentioned did really help...what happened is that I ended up replacing the EEV with the coil because the 4 degrees drop within 1 minute was too slow, but not after replacing the EEV & coil...bear in mind that the thermisters that were replaced were proven to be faulty in relation to its resistance test and temperature reading as seen on the remote controller.
Things looking brighter and life more relaxed, thanks Ozairman & Andy AC for making life much more fun for me now....appreciate the help...thanx guys.

Hi Taaz
Thanks for the feedback, you have shown way more aptitude than most of the people I spend my days talking to!
With regard to the EEV's the Fuji Koki EEV coils can give problems if they are the 6 wire type, later coils only have 5 wires. I think every Japanese AC manufacturer that used these has had issues with them over the last 5 years or so. There are internal connections in the coils which start making intermittent connections and you get random operation from the valve. Its easy to check on MHI units as you can see the EEV command pulses on the remote. Other symptoms are a unit that pumps down as the coils tend to only drive one way and it always tends to be closed!
If you had to change the valve bodies themselves as well then the main reason they tend to cause issues is due to a buildup of crap inside them, which most times is due to installation.
Cheers
Ozairman

Taaz1275
18-02-2013, 06:25 AM
Hi ozairman,
The unit which has had its EEV coil and valve replaced has been operating since my last post without any follow up due to the work load we've been facing ever since but now that things are slowing down, we most probably will be tending to investigate soon, and to see how well the unit has performed given the work done on it previously.
I new workmate of mine that has just joined in and was with me the last time we were out testing the thermisters and looking for the temperature differential readings on the remote controller just as you mentioned....thats was when he reckoned than that the EEV was the most probable cause to the delay in the temperature difference that the thermisters picked up which triggered the E57 fault just like you mentioned..
Anyway, ..one of us will be attending to the unit to investigate the progress of how well that has done for us....whoever attends I will surely have an update soon on where this all leads up to....
But thanks to you Ozairman ,..for pointing to us that direction we needed to take ...cheers!