MFI APM 6855 Integrated Fridge Freezer

Re: MFI APM 6855 Integrated Fridge Freezer

Hi Bob … many thanks for taking the time out of your busy work schedule to answer my post … much appreciated. I’ve just arrived home and eager to see if anybody has replied to my post. I have already placed a magnet just to the left of the LCD Unit (in line with the magnet attached to the top edge of the freezer door)and as you correctly said, the LCD went dim and the internal light went out. I can’t recall if the cold air came out of the air pipe, but I had the rear panels off at the time, freezer door open and I observed that the fan started when the magnet was placed to the left of the LCD unit and then it would stop when the magnet was removed. The small plastic cover on the inside front right hand side of the freezer that you mention … what I did with that was, after killing the mains supply, I prised off this small cover and saw a small pcb board, located on the rear of the cover which seemed to have a silver coloured type of resistor on it. This small pcb unit was connected by a small two pin connector to another connector block on the appliance wiring loom. I separated the connectors and made a temporary by-pass using a paper clip whose ends were pushed into the connector block on the appliance wiring harness side. I then reconnected the appliance to the mains supply and observed that the fan located on the freezer back panel started to spin. To be honest, I didn’t try putting a magnet over this small panel before prising it off and separating the PCB board from the appliance wiring loom, I’ll try that step later this morning when I visit my daughters and see what happens. If you don’t mind, I’ll go back through the steps that you have suggested mid morning (appliance is approx. 16 miles away)and submit my findings via the forum sometime in the afternoon. Is there a particular sequence in the activities that you suggest that I should follow? I’ll check out the small hole that you mentioned in the bottom right of the back panel to see if there is any ice blockage. The appliance will be in use as my daughter hasn’t disconnected it yet from the mains as she has some food in the freezer. Hopefully with your added advice I can get done to the root of the problem and get the fault rectified.

Heading for bed, thanks once again for taking the time to read my post and reply to it.

Sam Ellis

Re: MFI APM 6855 Integrated Fridge Freezer

Hi Bob … checked the F/F yesterday … found the LCD display showing “H” against the Fridge temp and -15 against the Freezer Temp also the alarm was sounding. My daughter said that the alarm had only started “beeping” a couple of hours earlier after she had opened the freezer door. I proceeded as follows, I opened the fridge door whilst keeping the freezer door closed and the internal lamp came on. I felt the fridge temp to be slightly chilled. I then placed a magnet to the left hand of the LCD display unit, the internal light went off, the display dimmed and when I placed my hand on the vents at the top of the air tube where the damper element is located, I felt cold air being pushed from them. I then removed the magnet, the internal light came on and the fan was heard to stop. I closed the fridge door and then waited a couple of minutes before opening the freezer door on it’s own. There was only one basket with food in it and the inside temp was found to be cold with some ice lollies still solid to touch. I located the small plastic cover half way up on the inside front right hand side freezer wall. I placed the magnet over the block and the fan started. I then emptied the baskets and removed the rear panels to expose the evaporator unit and locate the small hole you mentioned on the bottom right. I observed that the top of the evaporator unit was covered completely in “frost”, the No Frost thermistor that I’d replaced was completely covered and also the underside of the unit directly above the drip tray was heavy with frost. I couldn’t see the small hole that you directed me to locate. I thought that the purpose of the No Frost thermistor was to prevent the build up of frost on the cooling pipes/fins. With the frost build up, it suggests to me that the evaporator fins are being choked up with this frost obviating the unobstructed flow of cold air around the unit. This further has me thinking that there maybe a problem with the “heater” side of the system not producing the defrost action necessary to keep the evaporator pipes/fins “frost free???” It would seem that placing the magnet over the sensor areas in the fridge and freezer, generates the expected outcome of the fan starting up, and stopping when the magnet is removed. With the cold air being pushed out the top of the air tube into the fridge area, it would suggest that the damper element is operating as intended. I’ve now disconnected the appliance from the mains (Friday mid afternoon)to defrost the evaporator unit in preparation for any further work that you could suggest I can carry out on the appliance. From this new information that I’ve provided, can you determine what is causing the problem, and how I can proceed to rectify it.

Regards, Sam Ellis

Re: MFI APM 6855 Integrated Fridge Freezer

Hi Bob … many thanks for your reply … especially at 10:03pm on a Saturday night. When I replaced both the No Frost and Freezer Ambient Thermistors, the appliance had been switched off from the mains for a few weeks, and the evaporator area was obviously dry and free from frost. I noticed the two black boxes you have mentioned on the freezer evaporator pipe. They were each clipped on to the same pipe, adjacent to the pipe in front of where the No Frost sensor was fitted to. I remember that these two black boxes were free to slightly rotate and slide along the length of the pipe that they were clipped to. When I had completed fitting the two replacement thermistors, I slid the two black boxes along to the extreme left hand side of the evaporator pipe so that they were next to/touching each other. I made that decision, as at the time I didn’t know whether or not they were to be located at opposite ends from each other, but when I slid them apart, I observed that the tension in their cables, pushed them back in towards each other. Should they be clipped upright to the pipes using some mastic as found around the cable bung leading through to the PCB board on the outside rear of the appliance, to stop them from moving, or by plastic ties? They weren’t located on the pipes with anything to keep them in place. I’ll look at this next “challenge” tomorrow or Monday. Now that I’ve disconnected the appliance from the mains, the thermal fuses wont be covered in frost. I assume that I have to disconnect them from the same PCB board that the replacement thermistors are connected to? If I then connect an Ohmmeter across each of the thermal fuse terminals, (they would be at room temp at this point)should there be a set resistance value? If I placed each of the thermal fuses in the freezer cabinet of my daughters small table top fridge say for 15~20 minutes, withdrew them, then connected my ohmmeter across their terminals, then they would be faulty if there were no resistance (meter reading) shown. If they are faulty, would they be supplied and replaced as a pair? If the fuses are proved to be OK, is the replacement of the heater assembly a task that can be undertaken by myself, or is that a task for a refrigeration engineer?
Once again, many thanks for taking the time to read and reply to my posting. Sam Ellis

Re: MFI APM 6855 Integrated Fridge Freezer

Good morning Bob … many thanks again for taking the time to reply to my post. I’ll check them out today (Monday) or Tuesday. Could you tell me the function of/and where in the heating cycle the thermal fuses come into play? I often find it helpful to apply a “systems approach” to problem solving, it helps me understand/diagnose problems much more easily. Hence all the questions I’m asking you. (I have a BA degree encompassing systems analysis and design plus systems failures) If the fuses are faulty, what would be the root cause for them faulting? The heater unit overheating? Since the thermal fuses are associated with the heater system, would replacing them, only cause them to quickly “blow” again, not knowing the root cause? Is it possible to check the heater unit with a meter insitu? Are there any visual indications of overheating that can be observed when I’m working in the area of the evaporator?
Once I’ve checked out the Thermal Fuses, I’ll see if I can track down a knowledgeable engineer regarding replacing the heating unit. I suspect that replacing the fuses, then the heater assembly, plus an engineers time might just render the completion of this “project” as beyond economic repair? Anyway I’ll let you know the outcome of having the fuses checked, then maybe you can advise me from there.

Sam

Re: MFI APM 6855 Integrated Fridge Freezer

Hi Bob … spent some time last night removing the two thermal fuses from the evaporator. I proceeded as follows: (1) I tested both (at room temp) with my ohmmeter and the reading I obtained was 0.2 Ohms. (2) I then placed the thermal fuses inside the ice making compartment of a small work top fridge, routed the cable connector to the outside of the fridge to enable me to gain access to it, and left them in there for 25/30 minutes. (3) With the Thermal fuses still in the ice making compartment, I connected my ohmmeter across the connector block terminals, again the ohmmeter showed readings of 0.2 ohms for each fuse. (3) I removed the fuses from the ice making compartment and placed them in a teacup of hot water poured from the hot water tap (not boiling)and again, took a reading across each of their connectors, again the ohmmeter showed a reading of 0.2 ohms. Markings on these fuses were, “ITW ISPRA 72 42 05”, the 72 was proceeded with a superscript 0, I assume indicating 72 degrees? (4) I then disconnected the two push-on connectors associated with the heater from the pcb board. I took a reading across the two push-on connectors and obtained a reading of 8M ohms. (5) I checked the small square hole in the lower right hand side of the evaporator unit you mentioned in an earlier reply, and found that to be clear. (6) Refitted the push-on heater connectors to the pcb board. (7) Refitted thermal fuses to evaporator pipe and reconnected connector block to pcb (8)Reassembled all other parts and put appliance back in housing. (9) Reconnected appliance to the mains. (if it behaves as it done after fitting the new thermistors, it should develop same fault in about a weeks time)

Bob, from this further information, can you determine the root cause of the fault? Where do you think I should go from here?

Regards,

Sam Ellis