Brake Switch to Analog Input

I just would like to know if i’m allowed to connect battery voltage to analog inputs or will i damage the ECU?
I would like to connect the brake switch directly to the brake light.

Thank you very much!!

why not use Switch inputs ?

AIN is 0-5V. I don’t think I’d want to be testing it out with 12V.


You can connect the +12v to analogue in, it will not damage the ADC.

I strongly advise using CAM#2 input as a switch if the input is available.



The car doesn’t have a brake switch because of it’s age. It’s an old VW Beatle. And i don’t think you can use +12V on a Switch Input.

CAM#2 is available. I will connect the Brake Light to this Input. Thank you!

K lets nip this in the bud before it gets said again

You CAN safely connect 12V to an analog input.

The analog inputs are just looking for voltage. They do only measure up to 5V but for a switched input this is fine.
Now that said the CAM #2 input if not in use is a better input to use as it doesn’t tie up an analog input or risk altering the sensor ground, but it will not damage the ECU.

@sven kinda doesn’t, but it would have to have some switch for the brake lights somewhere, its probably pressure based instead of mechanical on the pedal like on newer cars. It’s still going to be 12V so where ever its easiest to get the signal from.
Ensure your CAM #2 settings look like this when you go to set it up


Thank you very much!


What about the input switches #1-#3? Will they be damaged if i accidentally put 12V on them?

They are designed to be connected to ground. I don’t think they would be damaged but they are pulled up to the 5V onboard power supply so I’d strongly recommend not connecting them to 12V.

Yes i totally agree with you. The reason why i am asking is the PNP adapter for the VW 1.8T Bam engine. The brake and clutch switches pull the switch inputs up to 12V when active or vice versa. Maybe the Adapter has some interanal circuit to convert the 12V to a ground signal.

I just read about the switch inputs yesterday afternoon and had no time to check if the signals will be converted accordingly. Hopefully they will and if not the 12V do nt damage the input.

Hi Folks,

in the last days i disassembled the BAM 1.8T Adapter and found out that there is no circuit to adjust the brake and clutch switch inputs from 12V to 0V and High Z.

So watch out which kind of brake and clutch switch your car has. Some of them may have switches that closes to GND when activatedn or vice verca.

Since i have built in the adapter into a US Passat there may be differences.

I also have to admit that my cabeling was not correct and the 12V never reached the 5V of the Switch inputs. (My car is an Golf 3 with 1.8T Anb enginge from US Passat with Passat harness)

I hope this information helps somebody! :slight_smile:

Best regards