I have a 2000 V70XC with 225,000 miles. I just had the engine replaced with a used motor. The ABS light was on and the speedo and odometer did not work when I picked up the car. Mechanic did not know why. I needed the car so I picked it up and started driving it. I found the battery was going dead after a few days. I had the "old" alternator put in the car but the battery is only reading 12volts when running. I consulted another shop and they told me it was my ABS control module. The ground for the alternator is somehow connected to the control module. I had the ABS control module rebuilt and my speedometer, odometer now work fine...ABS light and Check Engine lights are off. Car is still killing batteries. Anyone know why I am only getting 12 volts out of my alternator. Thanks for responding!

Tirewall

 

No ideas? Thanks for viewing!

 

Look for a ground wire not hooked up. The missing ground means the circuit that' missing it is finding another route. That route remains "on" while the car is off, draining the battery.

 

Mechanic resolved the problem...the alternator was only putting out 12volts because a wire on the starter looked tight but was not...it is somehow interconnected with the alternator. Getting plenty of voltage now!