Gen 1 Battery Drain

[FordTechOne]

Hi Everyone. Well, I thought we had the truck fixed, but while driving home the other day the large battery symbol appeared on the gauge cluster.

Is it possible the alternator we bought does not put out enough amps to keep the truck running and charging correctly? We had the alternator tested on the truck at Oreilys, but that's just at idle. I'm guessing there is more demand on the electrical system at speed? I'm also thinking I need to have the alternator tested at an actual automotive electrical shop. Not a chain store.

The alternator tester should test the alternator under a load to replicate the electrical load of the vehicle. Even 10 years ago most auto parts stores had that equipment, did they test it like that?

Also, battery light/low charging voltage can be more than just a bad alternator. A connector or circuit issue can cause the same thing. A common failure point is the connector at the alternator, they can develop poor pin fit and high resistance due to thermal cycling.

 

[P4SHOCAT]

I would take the battery out and charge over night. Test with voltmeter while charging, should be 13-14 volts while charging. Take off charger and let sit for a hour or so. A good battery will read 12.8 volts. If lower replace with at least a 750 CCA battery. AGM recommended.

 

[Pete_n_SoCal]

OK It's officially fixed. Took the alternator to an actual auto electric place. During the bench test the output was good at some RPMs and nothing at other times, but not consistent. It would be OK at idle, then dead at high RPMs, but then the output would be good at high RPM and dead at idle.

Took the case apart and the rotor had broken wires on it. The copper winding. Installed a new, not rebuilt alternator and life is good.

Thank You to everyone with your suggestions.