Repairing BOSCH B20CS30SNS/01 fridge

[jcdammeyer]

Alarm went off when temperature rose in freezer. System test reports L 00 through L16 and does not result in an ERROR __ value.
Fan runs cooling the external coils. Compressor does not come on. Suspect either control board relay or some other board relay or else the compressor is toast.

Fridge is 12 years old.

Suggestions? Control boards run over $500 and there are several not to mention cost of service call. Equivalent fridge is in the $3500 range assuming inventory is available.

 

[Janger]

ideas John....
1. bad crimp on connector? I had a bosch dishwasher fail due to a bad crimp on the heater coil. The wire melted off.
2. apply power manually to compressor to see if it still works? Sounds like lots of disassembly and work.

Best - J

 

[jcdammeyer]

This is what the motor control board looks like on the bottom:

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Essentially 110VAC in 220VAC 3 phase out. According to the bar code number the control signal is a frequency. It measures about 2.5VAC. The power into the board is 120VAC. The fuse on the bottom left corner shows continuity.

The bottom of the plastic box is slightly discoloured in the area around the 6 driver transistors on the bottom of the board and the bridge drivers close to the motor connector.

So either the driver board is shot or the compressor itself is shot.

Used ones run up to $200 with no guarantee that it's the problem. Compressor is 12 years old. Methinks I'm better off to just replace the fridge.

Can't figure out how to get at the main control board from either inside or from the back. The back panel is held with a number of screws and a bunch of rivets. Even with all of them removed it still appears glued into place.

What a shame.

 

[Susquatch]

Amazing. A VFD run freezer. Who wuda thunk it! Wow!

At the risk of repetition..... Connectors connectors connectors...... But you already know that so I assume you already checked them all.

Easy to fall victim to the old blame it on whatever I can't see or understand trick. We've all been there, done that, no matter how much we should know better.... (Ask me how I know that......)

Given that it's basically a VFD based 3phase system, you ought to be able to put a scope on it and walk the signals back one step at a time. Obviously you can't simply jump the motor, but maybe you have a spare low power VFD to do that with.

 

[Janger]

It’s run by a vfd. That’s amazing. Why or what engineering reason is there to do that? Fridges are usually on or off ?

Have you got another vfd you could use as a driver to test the compressor? You could borrow mine if you lived close? Maybe somebody else closer by could if you don’t have one?

 

[Janger]

It’s run by a vfd. That’s amazing. Why or what engineering reason is there to do that? Fridges are usually on or off ?

Have you got another vfd you could use as a driver to test the compressor? You could borrow mine if you lived close? Maybe somebody else closer by could if you don’t have one?

We need those right to repair laws. Products should be disassemble able. (Is that a word?) I mean repairable.

 

[Janger]

I think the board is more suspect than the compressor given that heat discolouration you discovered. The substitute board is cheap enough. If it works buy a second? Add some cooling?

 

[jcdammeyer]

Back after a run to the various appliance places to see what we can get for the interim or as a replacement. Last year I promised my wife a wine fridge for Christmas but that never happened. We decided we'd rather have an apartment size fridge for wine and other things. And with that in mind that purchase never went further.

So we're thinking for now we may get that 'wine' fridge for downstairs, but put it upstairs until we decide if we need to replace the big one or repair but have to wait for parts. Seems most of the places around here don't have inventory. Inventory is in Burnaby etc. and delivery for some time at the end of the week or next week.

Now as far as testing.

I have a 3 phase driver that I was testing a 1/3HP motor with. I was thinking I could connect that to the compressor to see if it works but I have no idea which way to spin it. And I don't know if I'd toast the compressor by turning it backwards.

The alternative is to connect the fridge drive to the 1/3 HP motor. But according to the web, that particular drive requires frequency in to spin the motor. Bottom RHS of the drive photo shows a small bridge rectifier there so I'm guessing that it turns the frequency into a DC voltage level. And yes, that's where right to repair should provide way more information on how to test and rebuild these drives.

I think I'll take stab at connecting the fridge compressor drive to the 1/3HP motor. First though I'll put a scope on the control signal from the fridge to the drive to see what it's trying to tell the drive to do. If I can duplicate that then I can at least see if it will turn an unloaded 3 phase motor.

Oh and the higher end fridges run the compressors at different speeds depending on their cooling requirements. Apparently more efficient. All the high end fridges we looked at today had that feature.

 

[jcdammeyer]

Further tests show, relative to frame, each of the two control wires for the motor drive controller are 120VAC. Difference between the two is 2.5VAC. Frequency, measured with the scope relative to the frame is 60Hz. The control signal in is buffered through an optical isolator triac driver.

Now it seems there is a repair for these if the bigger FETs or other parts aren't smoked:

and his tester:

 

[Susquatch]

Now as far as testing. I have a 3 phase driver that I was testing a 1/3HP motor with. I was thinking I could connect that to the compressor to see if it works but I have no idea which way to spin it. And I don't know if I'd toast the compressor by turning it backwards.

This was bothering me too as I thought about it. If the current VFD Works, you can use your scope to see which phase leads which.

The alternative is to connect the fridge drive to the 1/3 HP motor. But according to the web, that particular drive requires frequency in to spin the motor.

What the heck does that mean? I no capiche. Of course it requires frequency. All AC motors require frequency. You totally completely lost me on that one.

Bottom RHS of the drive photo shows a small bridge rectifier there so I'm guessing that it turns the frequency into a DC voltage level.

Prolly just there to create a power supply for on board controls and smarts.

I think I'll take stab at connecting the fridge compressor drive to the 1/3HP motor. First though I'll put a scope on the control signal from the fridge to the drive to see what it's trying to tell the drive to do. If I can duplicate that then I can at least see if it will turn an unloaded 3 phase motor.

And also determine which way it is supposed to turn.

Oh and the higher end fridges run the compressors at different speeds depending on their cooling requirements. Apparently more efficient. All the high end fridges we looked at today had that feature.

Didn't know that. I would never have guessed. But it makes sense. Variable speed motors can save a lot of coin!

 

[jcdammeyer]

This was bothering me too as I thought about it. If the current VFD Works, you can use your scope to see which phase leads which.

I'm not so sure it works yet.

What the heck does that mean? I no capiche. Of course it requires frequency. All AC motors require frequency. You totally completely lost me on that one.

Say you have a 3 phase drive like the one in the photo I posted earlier in this thread. It takes a POT or 0-10V input to create the variable speed out to the motor. The drive does that by varying the frequency while maintaining the 220VAC voltage to the windings

Now imagine you have my AC servo motor on my milling machine spindle. Still a 3 phase motor this time along with an encoder on the back. But the although the electronics can accept a 0-10V signal for velocity it can also take step/dir signals so you can even position the AC servo.

So I'm assuming that the fridge compressor accepts a frequency in of 53Hz to 150Hz which in turn results in the 3 phase driver electronics creating the 53Hz to 150Hz. Again not a lot different from a VFD that has a pot or 0-10V and creates 20Hz to 120Hz for example.

But I don't really know. The guys tester just couples the 60Hz line through the two resistors into the drive opto coupler input. On my the part number ends up being this guy:

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[Tecnico]

Alarm went off when temperature rose in freezer. SNIP! Suspect either control board relay or some other board relay or else the compressor is toast.

Fridge is 12 years old.

First off, given your youtube links I presume you've Googled for posts in forums like appliance repair. I never cease to be amazed at how often someone else has already had the same problem and posted a solution. My recent experience with a heat pump is just the latest. Looks like you're better equipped than me to understand the electrical side too.

My fridge story is the 4 year old Maytag that had a compressor fail, the sales guy laughed and said it was about right. Fridge before that I had the compressor replaced after about 15 years for a couple hundred bucks but nobody replaces compressors anymore.

It’s run by a vfd. That’s amazing. Why or what engineering reason is there to do that? Fridges are usually on or off ?

Oh and the higher end fridges run the compressors at different speeds depending on their cooling requirements. Apparently more efficient. All the high end fridges we looked at today had that feature.

The other reason for the VFD is it is probably used to minimize the noise emissions, partly because of controlling speed and partly by spreading out the (mechanical) power pulses over 3 phases compared to single phase.

IMO heat, showing witness discoloration is a marker (obviously the hotter they run, the shorter the life) but I'm inclined to suspect moving parts like the compressor.

Right to repair should also include having the product designed/manufactured to be worth repairing (blame marketing/bean counters not the engineers/designers) vs. throw away. That also comes home to roost when you look at life cycle waste of scarce resources and things like appliances filling landfills.

Down off the soap box.

Good luck with the diagnosis & repair!

D

 

[DPittman]

My fridge story is the 4 year old Maytag that had a compressor fail, the sales guy laughed and said it was about right. Fridge before that I had the compressor replaced after about 15 years for a couple hundred bucks but nobody replaces compressors anymore.

I've got a fridge in my basement that was my parents and is around 65-70 years old and I don't believe it has ever failed. The racks are and door handle are rough/missing but it runs like a charm.

 

[jcdammeyer]

Oh and this is the processor on the board.

https://www.nxp.com/docs/en/data-sheet/MC56F8013.pdf

The key element of the processor is:
"One multi-function six-output Pulse Width Modulator (PWM) module"
which provides the drives for the IR2304s

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which drive the 6 FETs which provided the PWM based 3 phase AC waveform from the rectified/boosted 120VAC to create the 220VAC 3 phase.

I've got a fridge in my basement that was my parents and is around 65-70 years old and I don't believe it has ever failed. The racks are and door handle are rough/missing but it runs like a charm.

Our little fridge downstairs and the top load freezer are both older than than the Bosch. But not nearly as sophisticated. I'll report back once I get capacitors in stock and replace them.

 

[Doggggboy]

This is too true

 

[Janger]

The old iron does seem to go and go but the old iron also uses something like four or five times the electricity. Might be $200 a year to run those old fridges.

Frigidaire seems to make fridges that work. After owning some Maytag gear I’ll never buy them again. An asko brand dishwasher came with the house. The manual states we expect this appliance to last 20 years. I’ve owned it ten years now. One problem only so far the drain hose cracked easy fix.

 

[jcdammeyer]

I worked it out but then deleted the posting as probably boring. Essentially the cost of the fridge over 12 years works out, with our power costs, to using about 310W per hour 24/7. That's not including the real power that it uses. I don't think the old inefficient fridges used that much power.

 

[Susquatch]

I still don't understand John. Perhaps there might be some fundamentals here driven by slightly different perspectives of how things work. Or maybe just your choice of words. English has to be the worst language in the world.

Say you have a 3 phase drive like the one in the photo I posted earlier in this thread. It takes a POT or 0-10V input to create the variable speed out to the motor. The drive does that by varying the frequency while maintaining the 220VAC voltage to the windings

I would have preferred to say that the VFD uses a 0 to 10 Volt signal to determine what frequency to output to the motor. The 0-10 itself doesn't create the output. The VFD creates the output using the 0-10 as a control signal.

Now imagine you have my AC servo motor on my milling machine spindle. Still a 3 phase motor this time along with an encoder on the back. But the although the electronics can accept a 0-10V signal for velocity it can also take step/dir signals so you can even position the AC servo.

Again, I'm confused. Does the Fridge motor have an encoder on it? If so, it isn't likely used for position control, just speed.

Many VFDs have a Sensorless Vector mode to determine speed. An encoder on the motor is not required in this mode. However some can use a sensor (encoder) on the motor to determine speed.

My VFDs are capable of being programmed to use both modes (and a few more).

But none of my motors have an encoder. So I use SLV (sensor less vector) mode. Does yours have an encoder?

Is there a chance that your source is confusing speed feedback with CNC position control?

So I'm assuming that the fridge compressor accepts a frequency in of 53Hz to 150Hz which in turn results in the 3 phase driver electronics creating the 53Hz to 150Hz. Again not a lot different from a VFD that has a pot or 0-10V and creates 20Hz to 120Hz for example.

Again, I think English is interfering with my understand and ability to follow you.

The majority of 3phase motors cannot handle the full range of frequency outputs that VFDs can deliver. So VFDs are often programmed to output minimum and maximum frequencies that are less extreme. 53hz is less extreme, but 150 is on the very high side. I presume this relates to the motors application bathed in refrigerant.

But I don't really know. The guys tester just couples the 60Hz line through the two resistors into the drive opto coupler input.

I confess I didn't watch the videos. I don't like YouTube and generally avoid it. So I can't really comment on this.

Generally, my observation is that most VFDs are capable of generating their own 10V reference voltage internally. The user can either use this voltage or generate their own externally. I assume that yours uses an external 10V reference simply because it has another controller board that determines the speed it wants to run at instead of a human being controlling it via a potentiometer.

 

[jcdammeyer]

Getting way too complicated. I was trying to generalize.
According to the data sheets I've found for this 115VAC 1Phase input to 220VAC 3Phase output driver is that some of them use a simple ON/OFF control and others use frequency input. As the photo of the label showed the output is 53Hz to 150Hz and the bar code # implies frequency input for control. It's not your typical VFD of the sort we refer to

Given that they are using a very powerful Digital Signal Processor the ability to analyze an input signal for frequency and generate a corresponding 3 phase output control is rather trivial.

All electrolytic capacitors age over time and it's likely the ones on this board are no exception so I've ordered replacements. The board is at least 12 years old and the marking on the board is 2008 so it's perfectly reasonable that the age of the capacitors might well be an issue.

I used the most expensive, highest quality, widest temperature range capacitors for the control of the lights on the Lions Gate Bridge. It's been running now since summer 2009 from dusk till dawn so not 24/7. But even so I expect that they will start having failures in the next few years. I hope not. So far they've been great.

 

[Susquatch]

Getting way too complicated. I was trying to generalize.

This is absolutely hilarious. Usually you seem to love complicated! But I agree it is complicated! And prolly too complicated. Mostly, I am trying to understand what you are saying because I get the distinct feeling I can learn something. I love learning. Sometimes that requires challenging the sources. I do appreciate your patience.

According to the data sheets I've found for this 115VAC 1Phase input to 220VAC 3Phase output driver is that some of them use a simple ON/OFF control and others use frequency input. As the photo of the label showed the output is 53Hz to 150Hz and the bar code # implies frequency input for control. It's not your typical VFD of the sort we refer to

Yes, part of the learning I referred to above. What the heck is this frequency control input all about!

And ya, it isn't typical. The mere fact that there is another controller controlling the VFD, indicates a significant step up in complexity and capability. Not that I need another project, but it also makes me think about doing similar things with the 3 VFDs I have in my shop. Not too likely to happen, but it gives my mind something to think about other than fixating on the other things going on in my life.

Given that they are using a very powerful Digital Signal Processor the ability to analyze an input signal for frequency and generate a corresponding 3 phase output control is rather trivial.

Exactly. But I'd love to know what it is that your fridge is doing that involves frequency input. My mind doesn't immediately embrace the need for such an input or analysis. Which implies that there is a chance to learn something cool!

All electrolytic capacitors age over time and it's likely the ones on this board are no exception so I've ordered replacements. The board is at least 12 years old and the marking on the board is 2008 so it's perfectly reasonable that the age of the capacitors might well be an issue.

Yup! Prolly a good call.

I used the most expensive, highest quality, widest temperature range capacitors for the control of the lights on the Lions Gate Bridge. It's been running now since summer 2009 from dusk till dawn so not 24/7. But even so I expect that they will start having failures in the next few years. I hope not. So far they've been great.

I hope not too.

But Awesome Lighting System! Does your contract include maintenance? Hopefully that doesn't mean crawling around up there......... I would die just thinking about it!

John - please don't let me try your patience. It's not my intent to challenge you. I'm really only insanely curious because the information doesn't fit my current knowledge base.

Feel free to bluntly tell me to pound salt or better yet provide a few links to explore on my own.