e89 roof problem

RobbiZ4 · Post by **RobbiZ4** » Fri Jul 30, 2021 9:20 pm

Pondrew wrote: ↑Fri Jul 30, 2021 9:06 pm ...so momentarily make the switches. Why would this have a bearing on the whole process stopping randomly?
Also, why would an ohm-meter be useful to determine the operation of a switch? A continuity tester, I can see.

Well, these microswitches are not only simple switches. They also carry 2 resistors internally, one in a row, the 2nd in parallel.
It's not a simple switch, there is always a current flow between the 2 wires of a microswitch. That's why you can diagnose it with an ohm meter: 570 ohms vs 2.770 ohms are the standard values.

The Cabrio Top Module (CTM) always checks the presence of all sensors as well as of all actors. If a wire is broken the CTM can identify it. If there is a short between 2 sensor wires , it can be detected as well. In addition, the 2 states OPEN as well as CLOSED.

The problem over the years arises by corrosion inside of the switches. Depending on the weather, the humidity inside of these microswitches can differ: the one day it works fine, the other not.

Pondrew · Post by **Pondrew** » Fri Jul 30, 2021 9:42 pm

RobbiZ4 wrote: ↑Fri Jul 30, 2021 9:20 pm Well, these microswitches are not only simple switches. They also carry 2 resistors internally, one in a row, the 2nd in parallel.
It's not a simple switch, there is always a current flow between the 2 wires of a microswitch. That's why you can diagnose it with an ohm meter: 570 ohms vs 2.770 ohms are the standard values.

The Cabrio Top Module (CTM) always checks the presence of all sensors as well as of all actors. If a wire is broken the CTM can identify it. If there is a short between 2 sensor wires , it can be detected as well. In addition, the 2 states OPEN as well as CLOSED.

I didn't understand most of that Robbie, but I know you have more knowledge than me.
However, I have taken one of these switches apart (just for fun and out of genuine interest) and cannot find any resistors in there.

RobbiZ4 · Post by **RobbiZ4** » Fri Jul 30, 2021 9:49 pm

Pondrew wrote: ↑Fri Jul 30, 2021 9:42 pm ... and cannot find any resistors in there.

LOL.
Where did you search for it?
You have to cut out the housing, then you will find a green circuit board. There are 2 SMD resistors soldered on it. One with 570 ohms, the other with 2.2kohms. In total 2.770 ohms, depending on the switch state (opened or closed).

Pondrew · Post by **Pondrew** » Fri Jul 30, 2021 10:06 pm

Nope, no resistors

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Ole gits rule · Post by **Ole gits rule** » Fri Jul 30, 2021 10:09 pm

Are they are SMT (surface mount resistors), tiny squares on the board maybe?

Pondrew · Post by **Pondrew** » Fri Jul 30, 2021 10:13 pm

Ole gits rule wrote: ↑Fri Jul 30, 2021 10:09 pm Are they are SMT (surface mount resistors), tiny squares on the board maybe?

Ok, where's wally?

Ole gits rule · Post by **Ole gits rule** » Fri Jul 30, 2021 10:14 pm

Pondrew wrote: ↑Fri Jul 30, 2021 10:13 pm
Ole gits rule wrote: ↑Fri Jul 30, 2021 10:09 pm Are they are SMT (surface mount resistors), tiny squares on the board maybe?
Ok, where's wally?

I cant see them either in your pic but it's the only thing I can think off coming from an electronics back ground

Pondrew · Post by **Pondrew** » Fri Jul 30, 2021 10:20 pm

Ole gits rule wrote: ↑Fri Jul 30, 2021 10:14 pm
Pondrew wrote: ↑Fri Jul 30, 2021 10:13 pm
Ole gits rule wrote: ↑Fri Jul 30, 2021 10:09 pm Are they are SMT (surface mount resistors), tiny squares on the board maybe?
Ok, where's wally?
I cant see them either in your pic. thumbsup:

That's because they are not there (unless they're hiding)

Ole gits rule · Post by **Ole gits rule** » Fri Jul 30, 2021 10:23 pm

Pondrew wrote: ↑Fri Jul 30, 2021 10:20 pm
Ole gits rule wrote: ↑Fri Jul 30, 2021 10:14 pm
Pondrew wrote: ↑Fri Jul 30, 2021 10:13 pm
Ok, where's wally?
I cant see them either in your pic. thumbsup:
That's because they are not there (unless they're hiding)

I can see fair amount of solder but that's it

RobbiZ4 · Post by **RobbiZ4** » Fri Jul 30, 2021 10:25 pm

Will post a pic of mine soon. Still on a bar trip...

Pondrew · Post by **Pondrew** » Fri Jul 30, 2021 10:29 pm

Ole gits rule wrote: ↑Fri Jul 30, 2021 10:09 pm Are they are SMT (surface mount resistors), tiny squares on the board maybe?

How can an SMT equal a surface mounted resistor?
Surely (and I am thinking logically here not technically) an SMT is a surface mounted transistor, an SMD is a surface mounted diode and an SMR is a surface mounted resistor!
As I said earlier, I am genuinely interested but so far am hitting a brick wall

Pondrew · Post by **Pondrew** » Fri Jul 30, 2021 10:31 pm

RobbiZ4 wrote: ↑Fri Jul 30, 2021 10:25 pm Will post a pic of mine soon. Still on a bar trip...

Maybe Germany get much better switches than we do in the UK. I blame Brexit

Ole gits rule · Post by **Ole gits rule** » Fri Jul 30, 2021 10:36 pm

Pondrew wrote: ↑Fri Jul 30, 2021 10:29 pm
Ole gits rule wrote: ↑Fri Jul 30, 2021 10:09 pm Are they are SMT (surface mount resistors), tiny squares on the board maybe?
How can an SMT equal a surface mounted resistor?
Surely (and I am thinking logically here not technically) an SMT is a surface mounted transistor, an SMD is a surface mounted diode and an SMR is a surface mounted resistor!
As I said earlier, I am genuinely interested but so far am hitting a brick wall

SMT means surface mount technology as opposed to pin and hole

RobbiZ4 · Post by **RobbiZ4** » Fri Jul 30, 2021 10:46 pm

.. and SMD is Surface Mounted Device! Not Diode.

SMD is a generalization for all parts.

RobbiZ4 · Post by **RobbiZ4** » Fri Jul 30, 2021 10:48 pm

Pondrew wrote: ↑Fri Jul 30, 2021 10:31 pm Maybe Germany get much better switches than we do in the UK.

Yes, of course. Your SMD's will be taken off as toll fees.

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