Samsung NQ70M7770DS/AA Microwave Oven Wall Combo - Microwave works but no heat

[zdmservices]

Model Number

NQ70M7770DS/AA

Brand

Samsung

Age

1-5 years

Hello! I have been troubleshooting this for months off and on and am at a standstill at this point. It all started with a C-A2 code which ended up being a burnt up power relay on the PCB. Samsung tech replaced the wiring harness, PCB, and right door latch/switches to no avail. After a third visit, Samsung basically said there is nothing they can do. At this point I've done the following:

-Replaced both PCBs and checked all the relays for functionality
-Replaced the wiring harness again
-Replaced the latch and all switches on the right side
-New magnetron and diode as well as magnetron TCO
-New upper and lower fans
-New thermistor for MWO (although it appears to be faulty)
-Confirmed functionality of all TCOs
-Confirmed functionality of transformer and capacitor
-All switches tested for functionality
-Tested several wires in the harness end to end to rule out shorts/continuity issues

The oven fully functions. However, the microwave will run on all settings (micro, convection, broil, etc) but will never produce any heat. Also, when the door is opened the magnetron cooling fan turns on but immediately shuts off when the door is closed. I also discovered that the thermistor for the MWO was testing at over 200k ohms but the service manual says it should read 1,080ohms. The replacement one (pulled from a scratch and dent) is also reading this so I'm wondering if it is defective or if I am doing something wrong. Sometimes the screen will read a C-20 error code which pertains to this sensor and the lower oven sensor. The lower oven sensor reads 1,080ohms which reinforces the idea that perhaps the other thermistor is bad. Looking at the schematic, it isn't clear if that is enough to trigger some sort of failsafe for the MWO. One would think this $4,500 unit would be smart enough to thoroughly diagnose itself but I guess that's asking too much.

Any help or insight at all would be greatly appreciated!

 

[actechrep]

Hello! I have been troubleshooting this for months off and on and am at a standstill at this point. It all started with a C-A2 code which ended up being a burnt up power relay on the PCB. Samsung tech replaced the wiring harness, PCB, and right door latch/switches to no avail. After a third visit, Samsung basically said there is nothing they can do. At this point I've done the following:

-Replaced both PCBs and checked all the relays for functionality
-Replaced the wiring harness again
-Replaced the latch and all switches on the right side
-New magnetron and diode as well as magnetron TCO
-New upper and lower fans
-New thermistor for MWO (although it appears to be faulty)
-Confirmed functionality of all TCOs
-Confirmed functionality of transformer and capacitor
-All switches tested for functionality
-Tested several wires in the harness end to end to rule out shorts/continuity issues

The oven fully functions. However, the microwave will run on all settings (micro, convection, broil, etc) but will never produce any heat. Also, when the door is opened the magnetron cooling fan turns on but immediately shuts off when the door is closed. I also discovered that the thermistor for the MWO was testing at over 200k ohms but the service manual says it should read 1,080ohms. The replacement one (pulled from a scratch and dent) is also reading this so I'm wondering if it is defective or if I am doing something wrong. Sometimes the screen will read a C-20 error code which pertains to this sensor and the lower oven sensor. The lower oven sensor reads 1,080ohms which reinforces the idea that perhaps the other thermistor is bad. Looking at the schematic, it isn't clear if that is enough to trigger some sort of failsafe for the MWO. One would think this $4,500 unit would be smart enough to thoroughly diagnose itself but I guess that's asking too much.

Any help or insight at all would be greatly appreciated!

Good afternoon, did you fix the Samsung combo oven?

 

[zdmservices]

Good afternoon, did you fix the Samsung combo oven?

Unfortunately, it was never resolved even after having been looked at by a high level robot tech and a couple engineer friends. Samsung should be absolutely ashamed that something of this nature effectively isn't repairable.

On the bright side, I played Samsung's game and eventually managed to get a replacement unit at no cost.

I do still have the original unit and would one day still like to figure out how to fix it. Since the PCBs, harness, and all of the power related components have been replaced, it really is a mystery as to where to take it from here. So if anyone stubbles across this forum and knows where to start, let me know!

 

[parm_2000]

Unfortunately, it was never resolved even after having been looked at by a high level robot tech and a couple engineer friends. Samsung should be absolutely ashamed that something of this nature effectively isn't repairable.

On the bright side, I played Samsung's game and eventually managed to get a replacement unit at no cost.

I do still have the original unit and would one day still like to figure out how to fix it. Since the PCBs, harness, and all of the power related components have been replaced, it really is a mystery as to where to take it from here. So if anyone stubbles across this forum and knows where to start, let me know!

I'm having the same issue with NQ70M7770DG model. I have replaced the magnatron, diode and capacitor checked the door switches Thermo fuses. Microwave just won't heat it did have a burnt connector on the PCB going to a relay the wire that burnt is for the fan near the magnatron the relay works just redid the crimp connector to have a better connection. No warning signs one day microwave just stopped heating the food. Other then that everything else functions as normal. Try to understand what the issue is no error codes.

 

[Kg135]

Unfortunately, it was never resolved even after having been looked at by a high level robot tech and a couple engineer friends. Samsung should be absolutely ashamed that something of this nature effectively isn't repairable.

On the bright side, I played Samsung's game and eventually managed to get a replacement unit at no cost.

I do still have the original unit and would one day still like to figure out how to fix it. Since the PCBs, harness, and all of the power related components have been replaced, it really is a mystery as to where to take it from here. So if anyone stubbles across this forum and knows where to start, let me know!

We’ve had the same issue and replaced the same parts. Was your unit still in the warranty period. Ours is not and Samsung refuses to help. This is such a common issue they should recall the unit. I hope nobody’s kitchen has caught fire. Had issue with oven where wires actually melted. $500 fix inky to have microwave go out