MFI AMP6855 defrost problem

[gliderpilot47]

I hope there is someone out there that has experience with MFI domestic refrigerators.

I had an engineer sent to look at an MFI 6855 which had a defrost problem. He decided the problem stemmed from the main pcb which was replaced. 3 weeks later we got a call from the customer saying they were having the same problem. I went out and defrosted the coil and checked some of the components myself. In the coil compartment there are two black (what I think are fusible links). Both of these, when tested showed continuity. The defrost heater was not open, but read about 500 ohms. There is a white (I believe to be thermister) sitting above the coil. What kind of reading should I get from this???. Also looking at the picture parts breakdown, there appears to be a rear mounted pcb. Does this pcb control the defrost cycle?

I am grasping at straws. The next vist will either be to refund the customer for the moneys already spent or fix the problem. MFI is no help. Europarts can only get their hands on a limited number of the defrost components. Knowing what I have mentioned, can anyone shed some light on this. We have one more chance at correcting the problem. I'm thinking rear pcb. The thermister is not available. Help!!!



Thanks in advance




david.vinyard@btconnect.com

[tonto33]

I'am a MFI service agent, the pcb at the back does control the defrost and the thermister is available..

[gliderpilot47]

I'am a MFI service agent, the pcb at the back does control the defrost and the thermister is available..

thanks for the information! is there a proper way to test the thermister

[brian m w]

Hi as an old mfi service agent my self, i have had more than my fair share of the apm6855 or shall we say the old service machines. The problem with the icing up is the suction line goes behind the air return for the fridge and causes the icing efect. No way to fix, Service just use to have them defrosted once and then replace them.

[Bachuss]

This modle (AMP6855) is probably made by some company in Tiwan as I have seen it with the Sheiber, MFI and now Diplomat. This problem is apperently Very common and from what I can assertain it is due to bad design rather than any fault.

Has anyone managed to find technical data in the PCB or other electrical drawings that they would be willing to share?

Is there any way to manualy start a defrost?