mattcmag

I have an 03 F-250 super duty diesel that the batteries keep loosing power. The batteries were tested and still good. not sure what is causing this issue.

R.S.LOGAN

If batteries are o.k have you tested alternator output or for a parasitic drain ?

Bajarider

Hello:
I had the same problem with my 6.0 Excursion. The voltage regulators fail due to heat. The alternator will then default between keeping the alternator connected to the batteries at shutdown, thus draining the batteries, or making no connection at all. (Don't forget that the voltage regulator does more than just regulate voltage). Make sure the alternator's airflow is not restricted by the hood insulation when you replace the alternator or regulator.