Mk4 Brake Assist Default Off

Further to a recent post on the forum.
I have had this 'feature' trigger for no reason, thankfully just the dash lights rather than the full brakes applied.  I regularly tow a boat and an Ifor GD trailer and the thought of this 'feature' deciding to fire off at 50mph whilst towing does not inspire confidence.  Indeed, reading through the user manual (section 2-73) it would appear Suzuki agree as it says to turn it off when towing or an accident could occur due to the system!  A "safety feature" that can cause an accident it seems - not so many years ago the idea of vehicles randomly applying the brakes for no good reason would of made headlines.

I know it can be turned off with the prolonged push of a button but I just do not want this "accident aid" defaulting to on.  With the addition of a 555 timer relay circuit, some small gauge cable and a plug and socket the default can be changed to off.  The switch can still be used to turn it on when required and it can be put back to standard without the use of tools or repairing cut wires.

This first link is to the 55 relay timer Quantity 1 @ 12v
www.aliexpress.com/item/1005005181688604...gatewayAdapt=glo2fra

This link is for the plug and socket I bought 2 in case I bu**ered up the first
www.aliexpress.com/item/1005002895195123...gatewayAdapt=glo2fra

In addition a permanent ignition switched live supply is required via a piggyback fuse to keep the circuit alive.
I'll add a circuit diagram and plug socket pinout next but I don't own a smartphone so there might be a slight delay.

555s aren’t particularly resilient to voltage spikes, I used one (IC/chip) in a circuit a couple of years ago and blew two before I put a socket in rather than soldering directly to the board.

I massively updated the 12v input regulator/filtering and it was then ok.

I assume that if you buy a module designed for a vehicle it is adequately protected.

Hi, yes I read something to that effect. I bought 5 of these modules as they are so cheap and expected some of them to be faulty, if not I would try to break one with over voltage, poor voltage regulation etc. which I have not managed to do; during testing I used a very poorly rectified 13.8vdc which simply caused both leds on the board to illuminate followed by a variable voltage supply stopping at 18vdc.

This mod does not introduce electronics into the cars wiring as such, only another switch (in the form of the board relay) in parallel with the dashboard switch. In the event the board looses power or goes faulty the relay closes and the vehicle sees the fault as too long a push on the dash board button - unplug board, fault is cleared.

When pressing the dash button to turn the feature off we are temporarily connecting the signal wire (plug pin 4) to the earth wire (pin 1).  A period of approx 6 seconds is required, hence the need for a timer circuit.  By placing another timer controlled switch in parallel to the dash switch - the board relay, we can automate the button press and at the same time keep the dash button.

The first photo shows the timer board.  Connecting the board to power brings on the red LED and the timer commences.  The time is defined by the blue potentiometer brass screw from 0 to 10 seconds, increased by turning the screw clockwise.  Once the timer has expired a relay click can be heard and the blue LED aluminates.  This can be played with on the bench with a 12 volt source to obtain approx. 7 sec delay.

We need to use the NC contacts on the relay so that the circuit is made with ignition on and then opened once the timer expires thus automatically turning the function off upon ignition on.

Second photo shows the circuit and the connector pin outs.  Pin 5 is not used, pins 2 and 3 are wired through from plug to socket and supply the dimmable light supply for the dash switch.  The only issue left is to pick up an ignition switched +12v supply to the module via a piggy back fuse wire from the fuse box.

The most difficult bit is wiring the pins into the plug and socket (especially if you are starting to need reading glasses!)

I will watch this string with interest, but in the meantime I am trying to train my memory banks to remember before each trip.
Switch that bxxxxy thing off!

Roger

ps so far, so good.

major clanger wrote:

Hi, yes I read something to that effect. I bought 5 of these modules as they are so cheap and expected some of them to be faulty, if not I would try to break one with over voltage, poor voltage regulation etc. which I have not managed to do; during testing I used a very poorly rectified 13.8vdc which simply caused both leds on the board to illuminate followed by a variable voltage supply stopping at 18vdc.

This mod does not introduce electronics into the cars wiring as such, only another switch (in the form of the board relay) in parallel with the dashboard switch. In the event the board looses power or goes faulty the relay closes and the vehicle sees the fault as too long a push on the dash board button - unplug board, fault is cleared.

I am not sure if it’s over-voltage that kills electronics, it’s probably more likely to be negative spikes in the supply rails caused when [inductive] loads are switched off.  Anyway if you have 5 of them at least you have a few spares and just because you have 5, you will never blow a single one.

Good luck with the mod.

Now if you decide to do a variable intermittent wiper, let me know.

Robin