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///M 'n it up!
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Discussion Starter · #1 ·
Does anyone know how to defeat the "brake safety" for the convertible top? I'd like to be able to put the top up and down without pressing the brake.

Here's what I do know. Last night I moved the top up/down button from between the seats, to the left of the DSC button under the climate controls; basically I just cut the connector and soildered in extension wires. While doing that, used a volt meter to determine the states of the control wires and how the button works. The button has 5 wires running to it. (Don't quote me on this, I'm doing it from memory)

Grey-Red is Power for Light
Brown is Ground for Lights
Brown-Yellow and Brown-Red are open collectors
Brown-Red is Ground for Controls

Basically the way it works, is when the brake is depressed, the open collectors go high (12v). When you then press up/down, the butotn connects on of the open collectors to ground, and therefore that open collector is pulled low.

My guess is that instead of building a $5 analog circuit of transistors and relays, BMW used a computer for the logic. When you depress the brake, the computer pulls the open collectors high. When you press the button, the line open collector line is pulled low, and the computer detects the change and runs the auto-top motor with the correct voltage (+12v or -12v).

In the case that my guess is correct, the answer would be to completely bypass the computer, and run my own wires and relays that control the auto-top motors. I could make the design fairly easily, its the find all of the wires parts that would be hard.

Anyone have any information to the contrary?
 

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///M 'n it up!
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Discussion Starter · #7 ·
Interestingly enough, I believe that simply switching the two relays depicted in ctop.pdf would defeat the "brake safety". Instead of being requried to press the brake to run the motor, you would be required NOT to press the brake to run the motor!

Infact, simply swapping the relays would also be the most efficient method. If one were to tie always on 12v to the brake input of the relays, the relays would always be drawing a current (probably the standard 40ma). By simply switching the relays, they would remain in their state of rest, and would be in a position that does nothing for the connected circuit when the brake is pressed.

I'll see if its physically possible to swap the relays and post the results here.
 

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///M 'n it up!
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Discussion Starter · #8 ·
ok, I swear I have purchased the ETM, but I still don't have it. Can you tell me where x18363 and x18364 (the auto-top relays) are located?
 

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///M 'n it up!
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Discussion Starter · #9 ·
I found two relays behind the driver's side amplifier in the trunk; both of mine are purple.

Unfortunantley they are both normaly open relays. The ctop.pdf clearly shows one of them being normally closed, which means my car's wiring doesn't match that schematic.

I am going to borrow some normally closed relays and see if that fixes the "problem".
 

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19,585 Miles
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wildag said:
I found two relays behind the driver's side amplifier in the trunk; both of mine are purple.

Unfortunantley they are both normaly open relays. The ctop.pdf clearly shows one of them being normally closed, which means my car's wiring doesn't match that schematic.

I am going to borrow some normally closed relays and see if that fixes the "problem".
The purple relays that I'm familar with have both a normally closed and open contact.
 

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///M 'n it up!
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Discussion Starter · #11 ·
Nope, that just blew fuse number 1 in the engine bay fuse box; 30A!

Back to the drawing board.
 

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///M 'n it up!
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Discussion Starter · #12 ·
Ron Stygar said:
The purple relays that I'm familar with have both a normally closed and open contact.
Aha! so it may be the wiring on the connector. I was really hoping to get away with a "no cuts" mod. :mad:

Well, since I'm an idiot and a glutton for punishment, I'm going to try to determine what would need to be "cut" and "modified". I'll wait until I get the ETM in.
 

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I'm not sure why you need this mod anyway. Speaking for myself and Randy, it's never been a big deal to hold the brake while raising the top with the car moving. Left foot on brake, right on gas. You don't want it going up/down at anything but low speeds anyway, unless you're looking for a quick way to destroy the ragtop and possibly other things. :)
 

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///M 'n it up!
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Discussion Starter · #14 ·
I want the mod because I drive about 1/2 a mile down a 5 mile an hour entrance way into a parking garage everyday. I'd like to be able to put up the top without looking like a monkey. Example: Left foot on brake, right on gas, left hand on steering wheel and right arm streched all the way behind my chair up to my shoulder trying to find the top up/down button while still looking forward (I'm short).

Moving the button helped alot, but now I'd like to be able to put the car in neutral, coast down the slight incline and put the top up while controling my speed with the brake (no gas needed down this incline to stay at 5 mph).
 

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wildag said:
I want the mod because I drive about 1/2 a mile down a 5 mile an hour entrance way into a parking garage everyday. I'd like to be able to put up the top without looking like a monkey. Example: Left foot on brake, right on gas, left hand on steering wheel and right arm streched all the way behind my chair up to my shoulder trying to find the top up/down button while still looking forward (I'm short).

Moving the button helped alot, but now I'd like to be able to put the car in neutral, coast down the slight incline and put the top up while controling my speed with the brake (no gas needed down this incline to stay at 5 mph).
So you're already applying the brake because you're travelling downhill, and the car isn't in gear. Hmm, what am I missing?

I can't count the number of times I've put the top up or down while moving. 'Lots' would be my best guess. Button is now up front, but I didn't have trouble doing it with the button in back before I moved it.

Don't get me wrong; there's nothing at all wrong with modding for the sake of modding.
Go forth and ignore me. :)
 

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///M 'n it up!
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Discussion Starter · #16 ·
I find "safety" features like this anoying. I'm not a frigin idiot, I know not to put the top up/down while traveling 80 mph. I want to be able to put the top up/down whenever I want, and not have any other constraints.

This goes along with what I did to my Accord. I rigged a remote start unit to be controlled by the seat belt, and I defeated the steering column lock. Remote unlock, get in, buckle the seat belt and the car starts; ready to drive - no keys. The "genious" part of this is that its still completely "factory"; the steering column lock could be fixed by removing a pin from the steering column. You can still use the keys if you want, and what thief is going to break into a car and buckle the seat belt? The funniest part? I sold it to a dealership with everything still intact. Somewhere someone is driving an accord that has a hidden switch in a box WAY up under the dash, that when flipped, alows them to start the car with their seat belt.

So in a nutshell, yes I'm going to keep ignoring the little birdies that roll their eyes :D
 

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Just a thought, and I'm not sure if it will work or not, but could you put a toggle switch in line with the break switch to simulate pushing the break? Flip the new switch, put the top up/down without using the break, flip the new switch again. This may also disable something else, but it may not be a problem for the length of time to put the top up/down.

Ken
 

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///M 'n it up!
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Discussion Starter · #18 ·
I do see your point, but it doesn't really work out. The toggle switch would have to be between the break light junction and the input to the top up/down relays. This means the switch would be in the trunk; unless I wanted to run an extravagant number of wires.

I am going to have to simply cut the wires that go to the two relays, and apply "Ignition 12v" to the "Brake input" lines. I suppose I could put a toggle switch back in the trunk with the relays... I'm just not sure I care enough for that kind of trouble.
 
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