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Thread: B22CS80SNS/01 Bosch Refrigerator working, freezer warm

  1. #1
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    Default B22CS80SNS/01 Bosch Refrigerator working, freezer warm

    Model Number: B22CS80SNS/01
    Brand: Bosch
    Age: 6-10 years

    I have a Bosch side by side refrigerator model B22CS80SNS/01 that has worked perfectly in the 2 years I've owned it (came with the house). Suddenly the food started to thaw in the freezer. The freezer is now blowing almost room temp out of the vent, and the refrigerator vent is blowing about 38 F.

    I tested the freezer compartment transducer using a table in the service manual. Resistance matched table values from near freezing to about 85F, as measured at the connector on the control board located on the top of the unit.

    I also ohm'd out the compressor, looks good with 7 ohms between each of the 3 pins. However, it's a variable speed compressor, and the inverter is only getting 2.3V DC. My understanding is that it should be 4-6 Vdc, but there is no value in the manual.

    This unit has two evaporators that share a single condenser, one evaporator in the freezer and one in the refrigerator. A solenoid controls refrigerant flow to each evaporator. Since one compartment is warm and the other cool, I assume the solenoid is blocking refrigerant to the freezer evaporator. The solenoid has two wires to it. I couldn't get the meter into the connector with it connected, but with it disconnected I measured 40V AC to ground on one pin and 0 V to ground on the other. I realize now that I should have measured pin to pin...but it was past midnight. Does anyone know how the solenoid is controlled by the 2 wires? It's labeled AWECO KMV432 120V 60Hz, so I assume it's AC. Couldn't find any info on it.

    I'm thinking it's a bad control board but don't want to buy the wrong part. To make matters worse, I can't find a wiring diagram for the unit anywhere, so I don't know for sure which of 3 boards control the solenoid or the inverter voltage. Service manual is terrible, doesn't give any info.
    Are there any other tests I can try? Any help would be greatly appreciated.

    Thanks! Brad

  2. #2
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    The problem is the main control board is not sending the correct signal voltage to the inverter. You're correct, connected to the inverter there should be approximately 4 to 6 VDC. Disconnected about 12-13 VDC. The main board is above the fresh food section. Replacing the board will reset the 3-way valve to the home position.

    650629 Control Unit
    Click image for larger version. 

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    OWNER RICK'S APPLIANCE REPAIR
    APPLIANCE TECHNICIAN FOR 31 YEARS
    REFRIGERATION SPECIALIST
    ONLINE SERV TECH: ApplianceBlog.com
    CERTIFIED TYPE 1; TYPE 2.....REFRIGERATION SERVICE E.S.

  3. #3
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    I installed the control board, still doing the same thing. 2.3 vdc to the inverter. How do check it disconnected? When I disconnect it the refrigerator won't start up at all.
    Thanks, Brad

  4. #4
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    I figured out why the fridge wouldn't work with the inverter unplugged. Two of the wires on that connector are the power cord. So I cut the DC PWM wires at the inverter and measured voltage and frequency with it connected and disconnected:

    With dc wires to inverter connected: 2.33 Vdc, 52.99 Hz
    With dc wires to inverter disconnected: 2.48Vdc, 52.99Hz
    I also measured 110V current to inverter with a clamp on ammeter. It started around .7 amps, but after running a minute or two settled at .42 Amps.

    The compressor runs, all fans seem to be running, but no cooling. This is with the new control board. I can't find a wiring diagram so I don't know which connector on the board supplies the inverter control. Even assuming the wires stay the same colors on the back side of the connector which I can't see, there are about 10 wires of the same size and color on the control board connectors.

    I think I could figure it out if I had a wiring diagram. I've never had an appliance that doesn't supply one...anyone got one?

    Thanks Brad

  5. #5
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    Hi Brad, looks like we had a little communication problem. I was under the impression, after reading your first post, there was no cooling because the compressor was not running. In your last post you mentioned,
    Quote Originally Posted by BradVA
    The compressor runs, all fans seem to be running, but no cooling.
    If the compressor is running and there is no cooling taking place there's a problem with the sealed system. It could be a refrigerant leak, system restriction, or a failed/inefficient compressor. Check your warranty. Some machines have a five year warranty on the sealed system.

    If you're the original owner and haven't had any service work done on it before there is a tech sheet/wire diagram somewhere on that machine. If you had work done on it there's a good chance the last tech stuck it in his tool box. Common places is under the door hinge covers, behind the lower grill, Taped to the bottom of the machine next to the condensor, and inside control housings. Some can fold up the size of a business card.
    Last edited by rickgburton; February 21st, 2017 at 10:03 PM. Reason: Added tech sheet info.
    OWNER RICK'S APPLIANCE REPAIR
    APPLIANCE TECHNICIAN FOR 31 YEARS
    REFRIGERATION SPECIALIST
    ONLINE SERV TECH: ApplianceBlog.com
    CERTIFIED TYPE 1; TYPE 2.....REFRIGERATION SERVICE E.S.

  6. #6
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    Thanks Rick,

    But if it were a compressor problem or refrigerant leak wouldn't the control board be sending 4-6 Vdc to the inverter? I'm only getting 2.4vdc to the inverter, which makes me think the compressor/inverter is not being sent the correct control signal. Is it possible that this inverter is supposed to operate at only 2.4 V?

  7. #7
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    Quote Originally Posted by BradVA View Post
    Is it possible that this inverter is supposed to operate at only 2.4 V?
    Bosch is not a popular brand and it's almost impossible to get any service information. Every inverter that I've seen so far regardless of brand is the same style inverter. They change 120 VAC to a high DC voltage using 4-6 VDC signal voltage from the control board. If the signal voltage is not correct the compressor will not run. I haven't worked on a Bosch machine with an inverter however it looks the same as all the others:
    Click image for larger version. 

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    Here's where I get confused. If your compressor is running then it's possible that inverter works with less signal voltage. If the compressor is running and there is no cooling the problem is in the sealed system. If the compressor is not running (which I suspect) then the problem is most likely the signal voltage. On whirlpool and GE machines, with the all the connections made, the signal voltage is 4-6 VDC. If the signal voltage is disconnected then you'll usually read the boards supply DC voltage (12 VDC- 13 VDC)
    OWNER RICK'S APPLIANCE REPAIR
    APPLIANCE TECHNICIAN FOR 31 YEARS
    REFRIGERATION SPECIALIST
    ONLINE SERV TECH: ApplianceBlog.com
    CERTIFIED TYPE 1; TYPE 2.....REFRIGERATION SERVICE E.S.

  8. #8
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    Rick, thanks for all the help. The compressor is definitely running, but seems to be running at a low speed. I found 2 other posts on your forum when i searched for 'Bosch inverter', and they both were complaining that the inverter was only being sent 2Vdc, so maybe they really do run on that low voltage or maybe its a common Bosch problem for the voltage to drop. The inverters you show in the picture sure do look similar. I even tried to call Embraco to get specs for the inverter, but they will only talk to professionals.

    I actually found the pins on the control board which supplies the inverter signal, so I know the board I replaced is the right one. Here's what the inverter control does:

    When plugged in, the fridge goes through self tests that take about 2 minutes. During this time, the compressor is not running and the inverter control jumps between 2.6 and 2.7Vdc at a frequency of 14.99 Hz. After self tests complete, the inverter control goes to 2.4Vdc and 59Hz and the compressor starts up. The compressor runs fast for a few seconds, then changes to a slow speed. A couple seconds later the inverter control drops to 52 Hz with the same dc voltage.

    Any ideas? I'm getting desperate and thinking of buying a piercing valve to check the refrigerant pressure. I've done some HVAC work and have gauges, vacuum pump, etc. But I hate to open the sealed system before I've tried everything...

    Thanks! Brad

  9. #9
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    Default B22CS80SNS Service Manual

    I was able to locate the service manual for that model. Signal voltage (page 46) 5-15 VDC. Bosch service manuals are very hard to understand sometimes. Let me know if you have trouble with it.
    Attached Files Attached Files
    Last edited by rickgburton; February 24th, 2017 at 07:46 PM. Reason: Added service manual
    OWNER RICK'S APPLIANCE REPAIR
    APPLIANCE TECHNICIAN FOR 31 YEARS
    REFRIGERATION SPECIALIST
    ONLINE SERV TECH: ApplianceBlog.com
    CERTIFIED TYPE 1; TYPE 2.....REFRIGERATION SERVICE E.S.

  10. #10
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    Wow, that's awesome. Thanks so much. I see the 5-15Vdc, very interesting. It'll take me a while to go through the manual, but this gives me so much more to work with.

    Thanks again!
    Brad

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