Alternator humming with key off.
Thread Starter
Joined: Aug 2012
Posts: 1,539
Likes: 84
From: Mesa, Arizona
Alternator humming with key off. Hey guys, I've run into a strange issue on another swap. I've tested a few things on this swap and compared it to mine and can only come up with one conclusion which is a bad PCM.
Problem is that the alternator is making a humming noise and draining the battery with the ignition off. I've already tested all the orange and pink engine harness wires and everything is wired properly to constant and ignition hot.
Pin 15 on RED C2 (generator turn on) is putting out 5 volts on this car with ignition off and 12 volts with ignition on. When compared to my car the wire is 0 volts until ignition is turned on and then 12 volts when on.
It's acting like the PCM isn't completely turning off this output.
Anyone ever run into this issue?
Problem is that the alternator is making a humming noise and draining the battery with the ignition off. I've already tested all the orange and pink engine harness wires and everything is wired properly to constant and ignition hot.
Pin 15 on RED C2 (generator turn on) is putting out 5 volts on this car with ignition off and 12 volts with ignition on. When compared to my car the wire is 0 volts until ignition is turned on and then 12 volts when on.
It's acting like the PCM isn't completely turning off this output.
Anyone ever run into this issue?
Had this issue when I did my swap. Alt is going to take a **** on you soon. The diodes are fried and you will need to replace the alt.
By any chance did you add any wires to the standalone harness going to the alt?
By any chance did you add any wires to the standalone harness going to the alt?
Thread Starter
Joined: Aug 2012
Posts: 1,539
Likes: 84
From: Mesa, Arizona
Hey thanks for the reply. The alternator was already replaced and is good. The car is using a 2002 camaro harness with the one signal wire going to it. The problem is the signal wire has 5 volts on it with the car off even when unplugged from the alternator. With the ignition on it does turn on and go to 12 volts.
I had the same problem with one of my swaps. All of a sudden it starting doing exactly what you are describing. Initially it worked perfect. I ended up just wiring pin on Alt to a keyed source with a resister.
