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B22CS80SNS/01 Bosch Refrigerator working, freezer warm

BradVA

Premium Member
Joined
Feb 16, 2017
Messages
9
Location
Portsmouth VA
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
 

rickgburton

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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
bosch-control-unit-650629-ap4513128_01_m.jpg
 

BradVA

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Feb 16, 2017
Messages
9
Location
Portsmouth VA
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
 

BradVA

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Messages
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Location
Portsmouth VA
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
 

rickgburton

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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,
BradVA said:
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.
 
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BradVA

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Location
Portsmouth VA
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?
 

rickgburton

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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:
Inverter Compressor.jpg

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)
 

BradVA

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Portsmouth VA
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
 

rickgburton

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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.
 

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BradVA

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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
 

BradVA

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Portsmouth VA
Rick,
I've gone through the whole manual and the part I'm having trouble with is the important page you referenced.

It says "Check the X4.5 and X4.7 in ASP. What does ASP stand for?

I'm assuming X4.5 would be connector X4 pin 5. Sure enough, the connectors on the main control board on top of the fridge are labeled X1-X9. But voltage between pins 4 and 7 of that connector is 101 VAC. ??

I cant find anywhere that describes what the function of the Power Module PCB inside the compressor compartment is. It's connectors are labeled CN1-CN7. One of the connectors has 120VAC in, I believe straight from the house, and the other 2 pins have 19VDc. Does this board produce DC voltage for the whole fridge?

I also ran though the Service Program on the display panel where you can turn on individual components and it gives the expected wattage. Measuring using a clamp-on ammeter on the power cord, I measured about 54W for the compressor instead of the ~100W listed, and about half expected wattage on a lot of the other things, but close to normal on others. My measurement method wasn't very accurate though.

Appreciate any thoughts or ideas of things to try.

THanks! Brad
 

rickgburton

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What does ASP stand for?
I believe it stands for Analog Signal Processor. Bosch uses a lot of abbreviations. I don't know what half of them stand for. That's why I mentioned that Bosch manuals are very hard to follow.

I cant find anywhere that describes what the function of the Power Module PCB inside the compressor compartment is. Does this board produce DC voltage for the whole fridge?
The power module supplies power to the control board, the IWD (Ice Water Display) board, and the lighting. I don't know if it supplies DC power for the entire machine but I believe it does supply DC power to the main control board.

But voltage between pins 4 and 7 of that connector is 101 VAC. ??
X4-5 and X4-7 is the 5-15 VDC for the inverter. Since you replaced the control board it's very possible the power board is the problem.

00627437 Control Unit
bosch-control-unit-627437-ap5657294_01_m.jpg
 

BradVA

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Thanks Rick.I tried unplugging the x4 connector and the control board seemed to run the same with it unplugged. The 100V at is in the connector, so it's coming from somewhere else, not generated by the control board.
Are you thinking the power module is supposed to send 5-15vdc to control board which uses it to make the 4-6 vdc modulated signal for the inverter?
 

rickgburton

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Something like that. Keep in mind I haven't worked on Bosch refrigerators very much maybe two in last five years. I'm kind of going by other inverter model machines which are not exactly the same.
 

BradVA

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Rick, thanks again for all the help. I finally talked to an authorized Bosch repair tech to find out how much it would cost to have him take a look. He told me something that may be useful to other DIYers working on Bosch refrigerators; my 2.4 V DC to control signal to the inverter is a normal voltage level for Bosch. I also managed to get my hands on an oscilloscope, and the signal was a nice square wave.

So based on your previous advise and the advise of the Bosch tech, I decided it was probably a compressor problem or refrigerant leak. I put a piercing valve on the low side and found out I had 0 psi with the unit not running, and a big vacuum with it running. I added the amount of R134a listed on the fridge tag, I think it was 7.4 Oz, and everything started working normally again. Obviously I have a refrigerant leak, so my plan is to see how long it goes to try to get an idea of how big a leak. I read somewhere that if it goes a couple weeks, R134 with stop leak may work. I have a leak detector, but have never had much luck with it but I'll try that too...plus soapy water.

Anyway, so far it's been 4 days and the freezer is still at 0 degrees F. Hoping for the best....Brad
 

kody

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British Columbia
Hey Brad,
I'm having a similar issue. My fridge is staying cold, but my freezer is warm. My fridge is actually icing up at the back, but my freezer is totally fine. Sounds like you didn't have any cooling whatsoever though in the end?

What did the Bosch repair guy tell you for a rough estimate?
 

pfbzzz

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us
Bumping this very useful thread. I'm having similar problems with my Bosch B22CS30SNS/01 again...

Problem:

RC stays 36-40F, regardless of setting
FC stays 10-20F, regardless of setting.

Diag info:

All fans working. Inverter board on compressor replaced about six months ago. Self diag tests show no problems.

Ice ball on RC evaporator, not all over but a big cluster of ice in one spot.

Status:

Technician who came out today (fairly basic level of knowledge) said it was a sealed system problem, he was not certified, different tech needed to come out and test.

Questions:

Does the ice blob vs. overall frost specifically indicate a sealed system leak? Might it not be a defrost problem instead? Tech did zero diagnostics or menu control of defrost functions.

If I want to troubleshoot the sealed system, I need to install a piercing valve onto the coolant line? I'm familiar with troubleshooting automotive AC sealed systems and have auto AC pressure gauges, but never worked on a fridge sealed system before.​

Next steps:

Give up on the old girl (and deal with all the potential problems of a replacement) or or continue to test/debug the defrost system and/or sealed system??​
 
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rickgburton

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Ice ball on RC evaporator,...Technician said it was a sealed system problem, Does the ice blob vs. overall frost specifically indicate a sealed system leak?
He's correct. It doesn't necessarily indicate a leak but a refrigerant shortage. It can be a leak or it can be a restriction in the high side. It can also be an inefficient compressor.
 

pfbzzz

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He's correct. It doesn't necessarily indicate a leak but a refrigerant shortage. It can be a leak or it can be a restriction in the high side. It can also be an inefficient compressor.
Thanks for the reply

Sounds like it's likely new fridge time...

Just for completeness, I defrosted the RC evap and tested the sensors (Good), RC defrost coil (good), Fans (good) and took this picture of the ice ball partially defrosted...

bosch fridge icing - 1.jpg
 
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rickgburton

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That looks like a sealed system problem. The evaporator is at low pressure so when the refrigerant enters the low pressure system it boils off. Where it boils off is where it gets cold and frosts. On yours there's only enough refrigerant to frost the first few inches of the evaporator.
[video=youtube_share;Hv-KNpdw0O0]https://youtu.be/Hv-KNpdw0O0[/video]
 
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