Dead Battery

[Corkwheats]

Hi Folks,

I have a battery that keeps going dead on me. It is a nearly brand new Interstate Battery. I have had the alternator checked at the local store - it's good. Once I charge the battery back up, and put it back in the truck (71 F100) it starts and runs perfect all day. Then, if I go to start it up a couple days later - dead battery!

Isn't there a Voltage Regulator that can go bad? Is that the next thing to try? Where would that be located?

Thanks,
Bob

[Nitekruizer]

A bad VR can cause the battery to die while the truck sits. I've had this problem several times with the electronic VRs. They short internally when the transistor fails and drain the battery through the alternator's field windings. (I've never had a mechanical VR fail)

One quick way to check is to feel the battery cable and the alternator housing with the engine cold. If the cable or alternator is warm, suspect the VR. Another quick way would be to disconnect the battery cable with the ignition switch "off" and all accessories "off" and the doors closed. There should be no sparks at all. If you do get sparks, try unplugging the VR and check for sparks again. There are other problems however, besides the VR, that could cause sparking when disconnecting the battery cable.

I'm assuming that you've already checked your wiring harness for shorts, bare and broken wires, etc.

The VR should be on the rad support between the rad and the battery, if no one has moved it.

I hope this is helpful.

[Nitekruizer]

You should be able to tell if the VR is bad because the system will likely be either overcharging the battery (upwards of 15 Volts @ battery) or it won't be charging the battery at all. I would do all of these checks.

[Corkwheats]

Thanks for the input, guys. Got a new Voltage Regulator from Advance Auto Parts for $21.99 (had it in stock). Installed it in a flash, and have had no battery issues since. We have a bingo!

Thanks,
Bob