Something is causing a drain on the battery, I have had the alternator changed, timing belt, when I rev the car the lights go away. But there seems to be like the car is cutting out when I’m driving it. I’ve had the vacuum lines changed as well. The mechanic said it could possibly be the ECU. I have had problems with the relay that is behind the B pillar that controls the fan for cooling the injectors. I need help

 

Need more info. Are you saying the headlights are going dim and finally go out while revving the car, and go back to normal when idling? Was this happening before changing the alternator? If so, were the symptoms th3e same before changing the alternator?

Once the car is running, the alternator should be running the lights. The faster the alternator spins, the more electricity it makes.

Put a volt meter on the battery terminals and see what the alternator is putting out at idle (over 12 volts) and while revving the car (over 14 volts). Won't be the first time a bad new alternator was sold.

As for the car cutting out, a bad alternator will make the car run worse and worse until the battery finally dies. In my case, the tach was reading lower and lower until the car would barely run. At 60 MPH, in 5th, the tach read 1000 RPM instead of ~2200.

Bad vacuum will also make the car run like crap, but not affect the lighting systems. So my vote is check the alternator first because it can cause both symptoms.