Samsung Refrigerator Defrost Timer Wiring Diagram

[Lina Drury]

Irecently have been experiences an issue with my Samsung RF18 where the both the refrigerator and freezer compartments defrost cycles are not working properly. It will cool properly (Refrigerator 38 degrees F, Freezer -2 degrees) for about three week and the temperatures will gradually start creeping up in both compartments, eventually the refrigerator will not maintain 45 degrees and the freezer 32 degrees and both evaporator are a block of ice, circulating fans continue to run but no air circulation due to evaporator icing.

I have checked condenser and and found clean (no dust bunnies) and no air way restrictions. I have also confirmed that the continuity of defrost heaters elements and associated over temperature devices on both evaporators are within specifications.

I contacted my local appliance repair facilities and none are willing to service the refrigerator with it in the motorhome. One of them was nice enough to provide me with a copy the Samsung trouble shooting guide and the electrical schematics.

I will run the diagnostic procedures tomorrow to see if determine why the evaporator defrost system are not working, I'm hoping that it maybe something as simple and a loose connection on the the wiring harnesses associated with the defrost circuits.

Jim, I had mine repaired in the coach, however I had to pull the unit out of the recess and have it where the tech could get to both the front and back of the unit. I had the part replaced and only had to pay for the labor. If I remember correctly the labor was about $300.00.

The Samsung RF18 is a high tech unit that uses a micro processor to control the defrost cycles. The refrigerator and freezer sections have separate evaporators and are controlled independently. Defrost cycles are only activated when icing is detected and duration of each cycle is variable.

Since the evaporator icing is occurring on both the refrigerator and freezer evaporators, it's leading me to believe that the problem lies with in the micro processor. The only reboot option is to interrupt power to the unit. have tried this with no success. I have run the self diagnostics and no faults have been detected in the temperature sensors and the only component common to both the refrigerator and freezer defrost is the microprocessor.

Jim, A number of microprocessor system's Do Not like the modified waveform generated by a number of the inverters. There are a number of manufactures that state that fact in there technical information. Many others do not specify the information. Modified waveform can mess up the clock and timing circuits.

I did not give a description of the timer mechanism. What I was saying is if you monitor the current to the defroster heater, assuming they are ok, then you can tell where the problem is. Measure the current and time to verify the circuit.

There many of the Samsung RF18 in RV's that are running on modified sign wave inverters. I contacted Samsung 4 years ago and was insures that the RF18 would perform without problems with on modifies sign wave power sources. The heaters are 120 v calrod heater the refrigerator heater 120 ohms (120 w) and freezer 60 ohms (240 watts). Both heater check OK

The builtin diagnostics allow you initiate the IO outputs for the different functions by operating the touch pads that control temperature setting. I have no voltage at the heater junctions on either heater. The processor output operated an ice cube relay mounted on the circuit. My next check it determine if the relay is getting a signal from the processor and to determine if there is 120 v at relay contacts.

Same refrigerator in my coach and the frig part defrost failed. Using the Samsung schematics I was able to locate the defrost heater leads in the rear of the unit and found I had an open circuit. Ended up being the thermal fuse located near the heating element. Cheap part but a pain to replace. I now carry a spare.

Contrary to what Samsung told you, I was tole NOT to run it on a modified sine invertor. Guest it's all in who you talk to. Regardless, I am using a pure sine and still blew the thermal fuse so maybe it really doesn't care.

I called them when we were shopping for a refrigerator also. All I got was "it run on house current only" . I made my way up their tech department and everyone was stumped. I gave up and bought a GE that I saw in a Fleetwood product at an RV show. GE told me Modified Sine wave inverter is fine as there are NO delicate electronics in that particular model. Its the computer circuits that usually will not run on MSW.

I had one of them too, but after 5 failures of the retro fit and reading stories of motorhomes with the retro fit still going up in flames I decided to make the change. When I removed my Dometic there was a section of charred wood adjacent to the stack. My brother-in -law is one of those whole lost his MH from a refrigerator fire,

I would like to modify my 3 year-old KitchenAid KRFC300ESS french-door (freezer on bottom) refrigerator to disable the auto-defrost cycle on a short-term basis, preferably by putting in a switch mounted near the front (ideally, connected the low-voltage control circuitry, not the defrost heater itself).

The motivation is that I'd like to be able to drive a few critical loads from a 1kW inverter, during short-term (few days) power outages. The inverter is usually able to handle these with aplomb, but during a recent power outage it could not (overloads and shuts off) even when I isolated so the fridge was the only load. I believe the auto-defrost must be the culprit.

I am a EE, and I'm comfortable going inside of appliances (in fact, I fixed a noise problem on this fridge that a tech could or would not). But I don't have the first clue how auto-defrost works, in theory or in practice.

Auto-defrost just raises the temperature enough that the accumulated undesired ice build up (very thin at this point) melts away while still cold enough and short term enough to not melt the items frozen in the freezer. It does this with a heater inside the fridge to periodically warm the appliance during the defrost cycle. Here's a video that explains it.

If you want to disable, you can find and remove or cut the wire to the heater. There should be a wiring diagram on the back and probably down low. Due to your background, I think that you can take it from here

At the rear of the freezer compartment there is a plastic cover held on with 4 screws. Behind that I should find the evaporator coils, and the defrost heater will be attached to that. If I add a small SPST switch in series with the heater, thing will function normally when the switch is closed. If I open the switch, the heater cannot operate.

During power outages when I'm trying to power essential house loads with the 1kW inverter, I'll open that switch. Seems like the worst that can happen is that the evaporator coils ice up; I can help that not to happen by avoiding door openings. But if it does happen, I'm no worse off than in the olden days before auto-defrost. I'd have to unplug the thing for awhile (perhaps a day) and let the coils defrost. Also, it appears the heater runs off 120vac, so I need to be careful with the way the switch is wired and mounted.

3a8082e126