E85-86 Convertible Top - Electrical Issue

[JamesZ42006]

I have a 2006 3.0Si Z4. Soft top worked 100% fine until a few days ago, when putting the top back up, it closed ~95-98% then just stopped and the red light at the up/down buttons started flashing. No noises, no hesitation, just stopped cold/dead. Turned car off/on, still nothing and red light flashing.


Pulled the red ring in the trunk, put it down the rest of the way and used the allen-key method to activate the windshield locking hooks and close it 100%. Red light still flashing; up/down buttons don't do anything - windows don't move, windshield hooks release motor doesn't engage, zilch.


Since it's a RED light blinking and not ORANGE, I didn't think it was the micro switch in the trunk for the shelf being down, but just to confirm I took my micro switch out yesterday and tested it w/ an Ohm meter and it does change values upon clicking and unclicking the lever; so I assume that works fine. And I haven't changed the truck shelf or had anything in the trunk for a long time.


Researching online, I found several discussions on this one, mostly due to the hydraulic pump failure due to water damage. I live in a dry zone, hardly ever rains, and the car is always inside, so hardly any water exposure, so I don't think I (luckily) have any issues w/ the hydraulic motor. And this seems to be a purely electrical problem.


I also took off the small access panel behind the driver seat and found the Convertible Top Control Module (white box). Unscrewed the mounting nut and pulled it out to check cable connections. Appears to be connected solidly, but I don't know if there's a way to check any specific voltages or continuity on specific pins to diagnose whether this module is working properly or not. Does anyone happen to know if there is a way to diagnose this module?


I could try buying a used module and swap it out, but don't want to waste the time/money doing that if it isn't the cause, or risk causing other issues putting a different, potentially faulty module in the car if the current one if fine.


I do have a basic BMW scanner and have this code: "22 Switch Cowl Panel Unlocked; short circuit to ground." I believe the "cowl panel" is at the bottom of the windshield (is that right?), so I'm not sure if this means there is something faulty with a sensor in the top bar of the convertible top that attaches/locks to the windshield..? Or if this could mean a cowl panel for the rear of the convertible top...?


Anyone experienced this electrical problem before and have any guidance?

[JAS1169]

I believe the cowl is the front of the top where it meets the windshield frame. Given your error code I believe you have a broken wire in the wire harness which runs from the white module to the front of the convertible where it locks into the windshield. However, there are two sensors in the front as well, your problem might be one of these. Your going to need to eyeball these sensors and there wiring connections.

If it's a wire in the harness you can either attempt to find the broken wire or get a new harness. Either way, you'll need to remove the roof line from the top (not all the way).

A fellow on the UK Z4 Forum had a broken wire in the roof harness. He pulled a portion of the liner and opened the wiring harness & found the broken wire and fixed it. Please look at the following:

https://z4-forum.com/forum/viewtopic...40610#p1840610

I would contact the original poster and run your problem past him. If need he should be able to give you tips on pulling the roof liner, checking the sensors and how to open the harness & check the wires.

[Clearancediver]

Realoem.com….. insert last 7 digits of your VIN

A lot harder to get correct place to do that as there is a tremendous amount of adware showing up on screen…. However once you get VIN inserted and accepted and then click on browse parts…. You get to where you want to be…

Finding what you want amongst the diagrams is another matter when it comes to electrical parts etc…. But persevere and you will be awarded.

What the code likely means is a switch failed in the folding roof and the motor that controls the locking mechanism is located in the top “cowl” which is the part that comes down and attaches to the top of the windshield

You have already accessed the area where that particular switch is likely located when you manually latch the top down.


Sent from my iPhone using Tapatalk

[JamesZ42006]

Thanks gang. I was able to take some parts off to access the wire loom and it appears there is a break somewhere near the bottom of the cable, as moving this slightly allows the top to work intermittently but then eventually stops. I am going to try to disassemble the paneling behind the driver's seat to access this lower part of the harness where it is "crimping" around the lever arm connection of the top, to see if I can find the break point.

[tedvadala]

i had the same problem broken wire fix that but now when top down does not unlock tu go up i have tu du that manualy

[JAS1169]

If you believe the issue is behind the paneling in the driver area, it is not the common wire break in the roof. Once you remove the paneling unplug the harness from the white box (convertible controller) and spray Electrical contact cleaner (Not costly) on both the harness plug as well as the plug area of the white box. Given the age of the car (I have an old one as well) it's a good idea to use Electrical contact cleaner whenever you unplug anything.
If this doesn't work, the controller might have failed and may need replacing.