Car window motor control output

I'm toying around with a car window, and used this tutorial to try and make it work:
https://itp.nyu.edu/physcomp/labs/motors-and-transistors/dc-motor-control-using-an-h-bridge/

I've set it up almost exactly as the tutorial says, however i supplied 12v as i've found that's what the control motor needs. Furthermore i removed the switch, as i want to control the motor movement directly from the code.

However, when i turn on the arduino and the power supply, the window only moves a little; quickly slows down and then stops (i can still hear the motor trying to work though). I measured the output to the motor while running, and it seems it's only getting around 1,5V from the h-bridge in the start, and it drops while running.

The arduino code i'm using is very simple:

const int controlPin1 = 3; // H-bridge leg 1 (pin 2, 1A)
const int controlPin2 = 4; // H-bridge leg 2 (pin 7, 2A)
const int enablePin = 9; // H-bridge enable pin

void setup() {
 pinMode(controlPin1, OUTPUT);
 pinMode(controlPin2, OUTPUT);
 pinMode(enablePin, OUTPUT);
 digitalWrite(enablePin, HIGH);
 digitalWrite(controlPin1, LOW);
 digitalWrite(controlPin2, LOW);
 delay(10);
}
void loop() {
 digitalWrite(controlPin1, HIGH);
 digitalWrite(controlPin2, LOW);
 delay(1000);
 digitalWrite(controlPin1, LOW);
 digitalWrite(controlPin2, HIGH);
 delay(1000);
}

The motor runs just fine when connected directly to the power supply (where i manually reverse the polarity), but it just won't work properly through the arduino + h-bridge.

I'm quite rookie to electronics, so it might be a rookie mistake i'm into. But halp pls.

EDIT: I realised that when i plug it directly to the power supply the current is around 2 amps, but when i plug it into the h-bridge the current starts out at 1 amp and then decreases. So it might be a current problem, however i do not have any other bridges to test with right now.