Trouble shooting Mr. Slim?

[george42]

Mr Slim Mitsubishi
Can someone give me a link for trouble shooting Mr. Slim? We have 5 of them. One has a pad on the wall the others have remote controls. The other day the pad went blank. I could not find a reset but pulled little plug, that tested 11V, on the board in the evaporator and that reset it. It worked for a couple of days and stopped. The display said Check P8. I’m thinking I should replace the board but I don’t like to just replace parts. If I take the cover off the pad there are a bunch of dip switches. I’d like to know what setting them does. Thanks.

[klrogers]

the website is http://www.mrslim.com but appears to be down at this time.

[klrogers]

The P8 code means that the outdoor section is not working, disconnecting the plug and plugging it back in reset the outdoor section.

[george42]

Thanks for the prompt reply. It's a beautiful day in Jersey I thought I would be the only one on today. The outside unit was full of acorns a mouse nest and a dead mouse. Since P8 means outside unit can i assume and replace the outside board or does that make an ass of me? You know what you are doing so are not part of assume. How could I check to see if the inside board is ok or not? When I reset it the outside worked for a while. It runs fine if I push in the contactor.

[klrogers]

The P8 code is activated by no temperature difference between return and supply, indicating that the outdoor section is not running(after a time delay). I would suggest that you get the outdoor section fully checked out, if there are pressure controls fitted it could be going off on high or low pressure, the control board is unlikely to be the problem.

[george42]

Thanks again. I don't think there are any pressure controls - I did't see any pressure switches. I'll check again on Tues.

[mrhvacmechanic]

If memory serves, P8 is the sensor on the outdoor coil. Please check slim site or you can call them and they will send manuals if you cant down load them.

[rabel]

George42;

Want a quick shot at fixing this problem???
-- change the condensor section contactor out--

I chased this problem for several days until I stumbled up and caught one running the compressor without running the condenser fan! Have now REPAIRED eleven of them so far, and in each and every instance, the contactor has been the culprit!

Robt.

PS Gosh, I wish that I could give a REALLY long-winded reply to this one!! ;-)

[bunglebear]

George42,

I work with Mr Slim day in and day out, having been trained and approved by Mitsubishi.

P8 could mean 2 different things, depending on the control system in use. There are 2 types, A and K. The easiest way to decide in on the gas. If it's on R22, then you have a K control, if it's R410A (I don't know if you use R407C) then it's an A control. The very last letter on the model number will be either A or K.

If it's a K control P8 means that there is an outdoor unit malfunction
If it's an A control P8 means that there's an abnormality in pipe temperature.

If you can email me back and let me know either the model number or "freon" type, I can talk you through it all.

Regards
James

[cybberman]

James any idea what P6 means? and what is the fix? Thanks

[bunglebear]

P6 means that the coil on the indoor unit is running either too cold-less than -15 F or over 70F. In cooling mode, which I assume is the case at this time of year it will possibly be icing up. Most common cause is dirty filters, or if not then check suction pressure and convert to evaporating temp on your gages. It may be a loss of freon due to a leak. If you want the codes, give me an e-mail address and I'll e-mail them to you. Let me know how you get on. I'd be happy to guide you through if you give me an idea of symptoms.

Regards
James

[cybberman]

Thanks James. Let me give you some background on this unit, it was installed and running perfectly in the front of the building, it was removed and reinstalled in an office in the back of the building not that it makes any difference. After it was installed and charged the unit would run for 15 minutes and turn off with a P6 error on the key pad. After working with it while we noticed that the High side, from the evaporator coil frosting back?

We vacuumed the system out again and recharged it to get a P8 error code on the key pad. It will run for about an half hour and turn off and give me the P8 error. Any help would be appreciated. That error code list would be great too. Please send the error code list to estichw1@optonline.net Thanks again!

[bunglebear]

Hi,

The 2 fault codes you are getting are related to each other. The P6 code is generated because of a freezing or overheat protection in the pipe or on the evaporator or condenser coil. If the temerature is abnormal as detected by the thermistor, the unit will shut down to protect itself. The causes of this could be a number of things. The most obvious would be bad airflow-I don't think from what you say that the filters would be blocked, if the fan on the indoor ubit is not running properly, the same effect would be had. Make certain that the fan on the outdoor ubit is operating correctly(although this would really only affect the system in heating mode if it is a heat pump). The frosting back on the discharge line could be a result of an overcharge of refrigerant, or a restriction in the liquid line as well as a problem with the reversing valve if fitted-so check that as well to make sure it is operating OK. What I would do is to follow the frosting on the liquid line to see how far back it goes and whether it leads to a blockage somewhere. This will be easy to spot as if there is a blockage, there would be a quite large temperature difference in the line across it. I notice that the unit has been moved to another office. If this office is smaller or has a much lower heat load than the area where the unit was previously installed the fault codes would be generated, due to either the operation at a temperature lower than the units tolerance range, or short cycling of air.
P8 code is generated because of an abnormality in the pipe temperature, the frost on the line would explain why you have this code, as the pipe temperature must be within a set range(which is the lower temperature between the evaporator temp and the liquid line temp-intake temperature-the thermistor needs to detect a temperature within 3 degrees C of this range, but thats not really important). It takes a minimum of 9 minutes to detect the fault Causes could be either a disconnected thermistor, or a shortage of refrigerant, defective reversing valve or even a piping fault (quite rare)make sure the maximum pipe run is not exceeded. Have you checked the liquid line temp where it leaves the condenser?.
There are numerous explanations and if you could give me air temps and suction pressures for this I could probably help yu to pinpoint the exact cause, but from what you have said already it is strange that the problem only occurs once the unit is moved so I suspect there is either a large reduction in cooling load, or perhaps the space to be air conditioned is much smaller causing the unit to short cycle cooled air back over the coil, giving the characteristics of an overcharged unit (assuming that the charge is completely correct)
Sorry for such a long winded reply, but if you could give me a bit more info, then I'm certain we would be able to nail it.

Best Wishes
James

[mastercool]

Man, after reading this thread I am getting kind of nervous......I was just on a Mr. Slim unit Friday, Model #PUG24CKB Serial #02260037 outdoor unit. Customer was complaining of it flashing the P8 code and he would have to push the on/off button on the wall keypad to "reset" the system. When I showed up it was fine, at first. I killed the power at the disconnect to check inside the outdoor unit, fan, piping etc. When the system tried to start again compressor locked up! Pulling 56 amps and then opening internal overload. I checked winding resistance values winding to winding - ok; I checked to ground with my megger - ok; I checked for low ohms short between windings - ok. I held my meter on the load side of the contactor while the unit tried to run, Volts steady at 238 dropping to 225 or so when compressor motor was pulling heavy current but I thought that was to be expected. Run Cap. value was right at 35 microfarad, I put a supco hard start kit across the run cap - same thing, actually compressor did turn over and take off at first but then siezed back up. I thought I had it in the bag - compressor locked up - but then reading that one guy's post about the contactors I'm nervous because a couple of times the outdoor fan did not start either. I considered replacing the contactor because of this but volts looked ok at load side and this thing is only a year old according to the customer and the single pole contactor looked to be in pretty good shape. So I'm worried because the customer was pissed and is going to call the installing contractor (not us) out on it and I don't want to look like an idiot when He shows up and replaces the contactor in 15 minutes and is done....hopefully that's not the case because this unit cools a Lab for testing asphalt compounds and they had to move sensitive equipment since I told them to leave the unit off on the roof!

[bunglebear]

Hi Mastercool

What you have there is a K control, system-should be running on R22. P8 on K control means that there is an abnormality in the outdoor unit. Changing the contactor will only work if that is the source of the problem-for instance if the contactor is not starting the fan then the code will show, and if the contactor is going bad, then changing it will sort the problem out. Check the contactor first. From memory I think the resistance should be 107 ohms. P8 will also be generated from a fault in the wiring between the two units, maybe a reversed connection, so check the wiring. But from what you are saying it sounds alot like an overcharge of refrigerant. The compresssor will pull heavy amps on startup if it's overcharged as it takes alot more juice to get going under higher pressures, and then if the overcharge is enough the compressor will go back out within a few seconds, especially if it's liquid slugging. Check the pressures and see if they are high if you can, otherwise you will have to reclaim the gas and weigh it to see.

Cybberman give me a few days to sort the fault codes for you, and let me know how you get on with the faulty unit-may also be wise to check interconnecting cable connections, but I don't think that's the problem-personally I would weigh out the gas and check the charge first, then move on from there.

Regards
James

[Edited by bunglebear on 08-01-2004 at 07:28 PM]

[cybberman]

Thanks I'll let you know.

[mastercool]

Thank you for the reply..........if an overcharge condition is the case, assuming it was this way from the start, couldn't that in turn cause scoring and "wash out" type condition on the bearings and shaft causing the compressor rotor to sieze? Is this something you run into often enough on these units to consider it a problem? (An overcharge causing the compressor to have insufficient starting torque for the pressure, I mean) There is a fixed orifice metering device so as long as a high differential pressure does not exist "across" the compressor, it's been my experince that a single phase compressor will start pretty reliably IF everything else is in good shape. She could be full to the brim w/ liquid and as long as the DP is not excessive (hard shut off TEV, etc.) she'll start and run until she chews herself apart :-) Especially when a start cap is added, again assuming the integrity of the motor and mechanism. I just wonder because I will remember that, if you find it (overcharging, I mean) to be a problem w/ these particular systems. Unfortunately I will probably not get the chance to go back there again until the customer calls and says Hey Dummy, it was just the contactor or the refrigerant, this is one of those deals. Yes this is running R-22, thank you for any info you can provide.

[bunglebear]

Hi Mastercool

The one thing I don't know is whether this situation has existed for some time. If there is an overcharge of refrigerant, then it will become apparent quite soon. If you say that the system's been running for some time, and no freon was added, then it is unlikely to be the case. I was assuming that this unit has just been commissioned, or not running for that long. Overcharging with Mitsubishi units will cause problems, depending on how much of an overcharge there is. It will be characterised by big draw amps when the compressor starts, it will run for a few seconds before shuddering to a stop, and generating a fault code on the controller-also check the LED on the outdoor PCB. All single phase compressors will have a start capacitor fitted as they are not self starting and rely on a phase delay to provide the starting torque, even so an overcharge would still affect the unit. It will start but not run. I assume you must have been talking about a hard start kit. If a large pressure differential does not exist, the problems still exist. The problem is not caused by the pressure (this just draws more current), but by liquid in the compressor, as these are designed only to take in vapor.
P8 codes are generated by a few things. Either it will be a wrong refrigerant charge, wrong interconnecting wiring, contactor (if the fan is not working properly), a reversed phase, the outdoor unit prootection device operating, or a damaged outdoor coil thermistor. You would need to check all the options. Check pressures with gages, check the wiring connections, and then check the components on the outdoor section, as well as any protection devices (HP LP switches etc). To check the outdoor coil thermistor, measure the resistance across it. If the resistance is normal, the outdoor control board would have to be replaced.
The problem is that it's always difficult to troubleshoot a problem from a computer screen, so I can only give you the facts of what can cause the fault. With more info temps and pressures and other readings I could probably give you an accurate diagnosis, but then again you could probably do that yourself. Feel free to contact me if I can be of any further help to you.
Regards
James

[Edited by bunglebear on 08-03-2004 at 04:16 AM]