BMW 61.35-1 394 205 Electronic burned

[Mato]

Hi to all,

sorry for the silly question but I am can't such here. I need to repair the  BMW 61.35-1 394 205 electronic. This is a simple control unit for a BMW 3 series 1987 electric roof. Is there someone who can help me with a schematic?

[shakalnokturn]

Schematic? Doubt it...
You could get some help but with better pictures after cleaning the soot. Bottom side would help.

4 relays likely for a H bridge (inverting polarity to the motor), my guess is you have a cooked resistor for current sensing (anti-jam).
The resistor could have fried due to one relay stuck closed.
The component the current sense is sent to could also have suffered. Not sure what all the rest is about.

[techman-001]

Schematic? Doubt it...
You could get some help but with better pictures after cleaning the soot. Bottom side would help.

4 relays likely for a H bridge (inverting polarity to the motor), my guess is you have a cooked resistor for current sensing (anti-jam).
The resistor could have fried due to one relay stuck closed.
The component the current sense is sent to could also have suffered. Not sure what all the rest is about.

The picture quality is poor as you say, and so it looks to me like the burnt component is a power Zener diode that has shorted out from a spike on the 12 volt system. This is very common and if that's the only bad part the board should still work, but the Zener should be replaced to prevent further damage to other parts. The Zener sits across the input battery voltage and in some designs with a small value resistor in series designed to burn out should the Zener short, and thus protect the pcb.

There may be a copper track that also burnt out when the Zener short circuited, again very common and easy to find with a multimeter on the resistance range.

The motor current sensor is probably that "U" shaped component at the bottom of the picture.

Repairing the board will be hard if any IC's are dead because like all automotive electronics it's covered in a very tough plastic(cky) coating.

A schematic is highly unlikely to be found anywhere, so I recommend tracing it out with a beeper, drawing up a schematic and releasing it on the Internet so it will help others with that board fault.

[Mato]

Hi,
Thanks for the answers. I want to publish as much as I can and find out about this electronic. The cars are oldies right now and have excellent collector value, and it will be a shame if this is not possible to repair or rebuild.

I have taken some more pictures in better quality. The protective layer is a pain in the ass to get poled down.

I think the current sensing happens on the left side with the big shunt resistor (a piece of steal).

 

[Mato]

some from the front

[Mato]

one more

[Mato]

and an absolutely hard to get service manual... (part 1)

[Mato]

and here is the part 2. sorry I hate to post 2 .pdf-s... if I posted one I can do this only if I reduce the quality and the .pdf is in low quality already

[techman-001]

some from the front

It looks like the burnt device is the series (fuse) resistor and the small round device above it is the overvoltage protection zener which I bet is shorted out. Replace the resistor, cut a lead to the Zener if its shorted (or you'll burn the replacement resistor out) and I bet the board will power up and run, but you do need to replace the Zener to provide overvoltage protection again.

[Mato]

Hi,
the part nr. 1 (Zener diode) is shorted out and have 2 Ohm resistance in both directions.
the part nr. 2 (Fuse?) in kind of funny. When I measured the resistance between the burnt resistor and the upper side(on the picture the place where the nr. 2 is ) from the fuse the resistance was 1.2 OHM on the other side 1.8MOHM. So I took it down and the part on is an open circuit now. If I measured the resistance between the resistor  (on the picture the pin that is " stand-alone" and (part 3 lower contact)) I get 5.6Mohm.
the part nr.3 (Resistor?) if I measured it I get constant 1,2KOhm... Can it bee that he has survived and that this is his real value?

Because I did not rip the resistor off. He has taken so much beading that his leg was melted away. 

What parts I need to get for replacement?
   

[eurgenca]

Hello.
Can you read markings on diode (part 1)?
From where are you?
Regards, Sebastijan.

[Mato]

Hi Sebastian,

The code on the Zener diode is BZT03C18. Sorry to all that I did not get this information before. With my naked eye, I was unable to see the information. With a microscope and some cleaning of the Zener, it was possible.

Link to the Zener:
https://si.farnell.com/vishay/bzt03c18-tr/diode-zener-18v-3-25w/dp/9398333

Sebastian, I am from Sentilj (near Maribor).

Best regards,



 

[techman-001]

Hi Sebastian,

The code on the Zener diode is BZT03C18. Sorry to all that I did not get this information before. With my naked eye, I was unable to see the information. With a microscope and some cleaning of the Zener, it was possible.

Link to the Zener:
https://si.farnell.com/vishay/bzt03c18-tr/diode-zener-18v-3-25w/dp/9398333

Sebastian, I am from Sentilj (near Maribor).

Best regards,

Replace the Zener with a new one and try a value around  10 Ohm 1 to 3  watt for the resistor replacement. I can't be certain what part you need but that is a typical value I've seen in other 12 volt automotive gear.

Optional: It would help to draw the circuit of the input voltage section with the Zener and resistor. If you can't do that, try and find a electronics technician who can ?

[eurgenca]

Hello.
I agree. Replace 18v zener diode and resistor with couple of ohms and check part 2. It is not a fuse i think that is diode. Desolder and check with multimeter. If broken try replace with BYD17D.

Seba.

[techman-001]

Hello.
I agree. Replace 18v zener diode and resistor with couple of ohms and check part 2. It is not a fuse i think that is diode. Desolder and check with multimeter. If broken try replace with BYD17D.

Seba.

The small tubular glass component (2) is probably a diode I agree.

[maginnovision]

Definitely not a fuse since the module has over current protection.

[techman-001]

Definitely not a fuse since the module has over current protection.

I never thought it was a fuse, in previous posts I said that the burnt device was probably a resistor which burns out when the Zener shorts.

The resistor burning out acts a bit like a fuse and usually prevents destroying copper tracks. I've seen plenty of them burnt out in different automotive/agricultural gear in the past.

Whilst the device has overcurrent protection for a jammed motor, ironically the overvoltage protection Zeners always short out and cause this exact type of board damage. I've never seen a open circuit Zener failure.

[Mato]

Hi,

techman-001 I tried to draw the input. I hope it helps.  I ordered the 10 OHM 3W resistors and the Zener diode. I hope I get it in a day or two. The problem is the BYD17D because I don't know where to get it. If I order it out of E-bay, it will take forever, and I can't find the component by a shop where I can get the part FAST.

eurgenca have you a hint for me where to get this?

[Mato]

I forgot...

I desoldered the component 2 and it simply fall apart. So I can not measure anything.

[techman-001]

Hi,

techman-001 I tried to draw the input. I hope it helps.  I ordered the 10 OHM 3W resistors and the Zener diode. I hope I get it in a day or two. The problem is the BYD17D because I don't know where to get it. If I order it out of E-bay, it will take forever, and I can't find the component by a shop where I can get the part FAST.

eurgenca have you a hint for me where to get this?

Well done, your schematic makes much analysis much easier.

12 volt power must come in on INPUT CONNECTOR 18 I think.

This is what I think happened , the Zener was shorted by a high voltage inductive spike from the alternator (very common) which cooked the series resistor and fused the input polarity protection diode.

There will be equivalents of the BYD17D Zener by other brands.

[techman-001]

I've redrawn your schematic to show the logical layout as I see it.

Don't worry about component 2, it's just a diode, probably a 1 -3 Amp 400V diode is fine.

[amyk]

It's an electric roof. I'm surprised it needs any active electronics at all.

I would be tempted to just rewire the whole thing with a few relays.

[maginnovision]

The problem with that is no open/close protection and if someone pressed the button while driving you might ruin your car. It can be actuated manually which is probably what I'd do, close it forever, unless I were selling it.