A68B Microswitch, roof shell 2 closed, left - Updated!

[True-Blue]

Afternoon all,

The Mrs car decided to throw a wobbler earlier today, with the roof stuck open and unable to open the boot.

The error code is per thread title, and from research it seems that this is normally a break in the wires rather than the switch itself, only thing is the car had a completely new roof loom by a BMW main dealer 2-3 years ago.

I thought I’d read something from ‘Robbie’ that suggested the microswitches in the 2nd clamshell never fail and it’s always the wiring.. but this seems a bit unlikely here.

I’ve also read that it’s possible to open the boot with some special software via a laptop.

Any thoughts anyone…. Wiring isn’t my bag so will probably need to get a local fix.

 

[B21]

Maybe the guys didn’t route the harness correctly and it’s failed..again?

 

[True-Blue]

Maybe the guys didn’t route the harness correctly and it’s failed..again?

Possibly, I’ve had a look and it all looks spotless under there with no evidence of frayed wires… I wonder if it’s a rare example of the code actually being accurate on this occasion.

Still need to get my head around the work around for opening the boot, something about fooling a sensor into thinking the roof’s closed

 

[B21]

Maybe the guys didn’t route the harness correctly and it’s failed..again?

Possibly, I’ve had a look and it all looks spotless under there with no evidence of frayed wires… I wonder if it’s a rare example of the code actually being accurate on this occasion.

Still need to get my head around the work around for opening the boot, something about fooling a sensor into thinking the roof’s closed

It is the Achilles heel of this model… :tumbleweed:

Pity I just love the convertible aspect of this car..

 

[flybobbie]

My experience the right tends to fail.
So was the new just the right side, now left has failed?

 

[True-Blue]

My experience the right tends to fail.
So was the new just the right side, now left has failed?

That’s a good question, and I’m not sure. I’ll need to work back through the paperwork that came with the car

 

[javis20]

Could still be a broken wire, if they incorrectly installed the harness.. Locate the 2 major bends in the harness on the left side. Grab with you hand and flex it a bit. If it's a broken wire, sometimes it will still make periodic contact and allow you to open the top.

If you have ISTA or Bimmergeeks Protool software, you can open the boot.


Otherwise, use pin 12 trick to open the boot.
https://z4-forum.com/forum/viewtopic.php?t=144888

 

[flybobbie]

But the odd thing the 3 breaks on my car all been on the straight sections.

 

[AnubisZed]

The factory replacement loom does NOT come with any microswitches, and the only ones you may need to change (on a full loom change), due to new connectors (as explained very well in this link https://z4-forum.com/forum/viewtopic.php?t=122363), are in the boot. So as most of the microswitches come with about 6" of wire connected from them to the loom plug, then this could be the issue here.

 

[True-Blue]

@RobbiZ4

looking for a bit of guidance please.

I’ve got into the boot and measured the voltage at pin 20 and pin 7, both read 12.5v with the ignition on.

My symptom is that the roof shell 2 goes so far up on the open cycle, then falls and bounces back up, and falls etc… Could’t it be that there’s a break in the signal wire which is in closed contact (making a circuit) when the roof is down so the roof tries to go up, but then breaks connection, so falls back down.. reconnects, tries to go back up breaks the cycle etc.

Currently can’t close the roof or fully open it, windows are down, and code is as stated earlier in the thread. I don’t want to get the roof elevated sufficiently and start looking for split wires if this isn’t likely to be the issue.

Many thanks

 

[True-Blue]

Further update…

Having checked the voltages on pins 7 & 20 they both read @12.5v

I’ve plugged the pin back in and reinserted the connector, re-read the fault codes and A68B has disappeared, where it was ever present?

I’ve still got a flashing red roof light, but this is hardly surprising as the boot is open and the roof isn’t closed, windows still down.

I’m toying with the idea of closing the boot and trying the roof again….

Any thoughts anyone?

 

[javis20]

I would try to get it down and see what happens.

 

[True-Blue]

I would try to get it down and see what happens.

Tried it, same again…. Bouncing and same fault code.

I’ve been methodical, checked the correct pins, voltage to both…. Hmm

 

[True-Blue]

Thinking out loud here…

Clear fault code and before trying to activate roof it doesn’t come back

Pins giving correct voltage when ignition is on and shell 2 is in lower (almost closed) position

Try to close roof, shell two starts to rise, then falls back and starts to rise… bouncing up and down

Fault code reappears

Clear code

Read codes again - no code

Try roof again - code

The logical part of my brain is saying break in wire that opens the circuit when shell 2 moves beyond a certain point, causing shell 2 to fall backwards closing the circuit again…

Am I losing it or does that seem like a logical deduction?

 

[javis20]

The voltage at the CTM connector doesn't tell you much. It can be few things.
1. Broken Wire
2. Defective microswitch.

For a broken wire, you could bypass the microswitch wires one at a time. Pull the pins at the CTM connector and plug wires in and route them up as close to the microswitch as you can. Beyond the drastic bends. That will confirm if wires are broken.

Another option is to buy a microswitch and wire it directly into the CTM connector and operate it manually. If the roof still doesn't work, you know it's not the switch or the wires. At this point look toward the hydraulics. Please take note, these microswitches are not open and close. Not pressed, they are 550 ohms and pressed they are 2.7K ohms. If can reach in to activate the microswitch, you can measure the resistance at the CTM connector. To verify the switch is good.

Concerning the boot, you can use ISTA software to trigger boot open. You can also use Bimmergeeks Protool App on an Android phone or tablet to accomplish this. Lastly you can go the connector block under the glove box and do the pin 12 trick to trigger the boot. Google pin 12 trick bmw z4. Very easy, you short pin 12 to a fuse for the 12v and it will trigger the boot.

If all of that doesn't help check you salmon relays. They trigger the hydraulics to operate the roof hydraulics. In fact you may want to check those relays first...

 

[B21]

The voltage at the CTM connector doesn't tell you much. It can be few things.
1. Broken Wire
2. Defective microswitch.

For a broken wire, you could bypass the microswitch wires one at a time. Pull the pins at the CTM connector and plug wires in and route them up as close to the microswitch as you can. Beyond the drastic bends. That will confirm if wires are broken.

Another option is to buy a microswitch and wire it directly into the CTM connector and operate it manually. If the roof still doesn't work, you know it's not the switch or the wires. At this point look toward the hydraulics. Please take note, these microswitches are not open and close. Not pressed, they are 550 ohms and pressed they are 2.7K ohms. If can reach in to activate the microswitch, you can measure the resistance at the CTM connector. To verify the switch is good.

Concerning the boot, you can use ISTA software to trigger boot open. You can also use Bimmergeeks Protool App on an Android phone or tablet to accomplish this. Lastly you can go the connector block under the glove box and do the pin 12 trick to trigger the boot. Google pin 12 trick bmw z4. Very easy, you short pin 12 to a fuse for the 12v and it will trigger the boot.

If all of that doesn't help check you salmon relays. They trigger the hydraulics to operate the roof hydraulics. In fact you may want to check those relays first...

 

[Dr-Jon]

Further update…

Having checked the voltages on pins 7 & 20 they both read @12.5v

I’ve plugged the pin back in and reinserted the connector, re-read the fault codes and A68B has disappeared, where it was ever present?

I’ve still got a flashing red roof light, but this is hardly surprising as the boot is open and the roof isn’t closed, windows still down.

I’m toying with the idea of closing the boot and trying the roof again….

Any thoughts anyone?

True Blue, if it helps you can trick the car into thinking that boot is closed (so the roof mechanism will operate ) while in fact it is still open.
If you open the boot and push a small screwdriver into the 2 off locking mechanisms when you push the second one up you should hear the self closing motor run, the car now thinks the boot is shut, the roof will operate, obviosly you would want the boot closed but as you have already locked it it will sit on the 2 soft close plungers and will be fine if the roof operates.
once your finished and you need to lock the boot again you can open it via the keyfob or boot handle and it will open the 2 off locks in the boot lid. close as normal then.
Hope this helps, it has helped me out a lot lately

 

[True-Blue]

Thanks for all the input…

I’m going to pop the boot again this evening using the pin12 trick (did this the other day, very straightforward).

I’ll check the Salmon relays, but fairly confident they’ve been replaced fairly recently.

Does anyone know how to safely bridge the left sensor with the right one to trick the roof into thinking both are good? This seems to be simplest rout to identifying if it’s the wiring/switch on the left that is faulty?

If this is the case, should also enable me to elevate the roof to better inspect the wiring etc without messing about with the pump itself.

Thank you very much again all

 

[javis20]

I really hate to post this video, here it is...

https://www.youtube.com/watch?v=3q52HtkK6mU


Nice video, but his wire repair was ass.

 

[javis20]

Further update…

Having checked the voltages on pins 7 & 20 they both read @12.5v

I’ve plugged the pin back in and reinserted the connector, re-read the fault codes and A68B has disappeared, where it was ever present?

I’ve still got a flashing red roof light, but this is hardly surprising as the boot is open and the roof isn’t closed, windows still down.

I’m toying with the idea of closing the boot and trying the roof again….

Any thoughts anyone?

True Blue, if it helps you can trick the car into thinking that boot is closed (so the roof mechanism will operate ) while in fact it is still open.
If you open the boot and push a small screwdriver into the 2 off locking mechanisms when you push the second one up you should hear the self closing motor run, the car now thinks the boot is shut, the roof will operate, obviosly you would want the boot closed but as you have already locked it it will sit on the 2 soft close plungers and will be fine if the roof operates.
once your finished and you need to lock the boot again you can open it via the keyfob or boot handle and it will open the 2 off locks in the boot lid. close as normal then.
Hope this helps, it has helped me out a lot lately