I do have a AMP. ALPINE PDX 4.150. I also checked if the hum was present with the ignition on but car not running. It was NOT there. It is only there when car is running. I also check in the engine bay for a CDI. I didn't see one? Could it be located somewhere else on a 89? Im in the process of checking all the grounds on the car. How many are there? I found the one on the AMP and there are 2 on the left and right hinges of the spoiler.
Rob G
Quote:
Originally Posted by ischmitz
CDI stands for Capacitive Discharge Ignition. It is the silver box with the cooling fins on the electric panel in the engine bay.
It uses a DC/DC converter that runs with 3.5kHz. To check if that is the culprit simply turn the ignition to ON but do not start the engine. If the hum appears it is likely the CDI unit. If the hum only appears when the engine is running it still could be.
The fact that the hum is NOT changing pitch with engine RPM makes me think you could have a ground loop. Are you using an amplifier or only the head unit driving the speakers?
Ingo |