77 f150 battery or alternator problems

Asked by Oct 23, 2013 at 07:01 PM about the 1977 Ford F-150

Question type: Maintenance & Repair

i recently chnged my alternator belt and today i tried to turn it on and my battery went low
again... whats eating my battery power...

8 Answers


2 out of 2 people think this is helpful.

...assure that the battery is newer than five....Tin/Antimony Alloy batteries (no lead anymore) will stop taking a charge 10 percent per year~


do yu hve any mods like subs hookd up to it

1 out of 1 people think this is helpful.

If your battery went dead from a bad alternator and you replaced the alternator, You MUST recharge your battery completely by a battery charger NOT your new Alternator. With a dead battery you can burn out the diodes in a new battery within seconds( YES, I said seconds) An alternator is only meant to recharge your battery after starting, not after it's dead. and it also has to power all your car accessories like power windows, fans, lights,etc while it recharges your battery. You might have ruined your new alternator already. Take your battery to an Autozone or similar and have them check to see if it's any good. If still good, have them charge it up while they have it. After it's fully charged or you bought a new fully charged battery, put that in the car then drive your car to the parts store that checked your battery and have them check the new alternator that you just bought. If your battery is fully charged, then and ONLY then can you install a new alternator. You might need to replace the voltage regulator also which should be mounted on the fenderwell near the battery. I hope you saved your receipts. Good Luck, Kenny/MrBlueOval

1 out of 1 people think this is helpful.

ahhh, ye olde voltage regulator~!

NAPA or any parts houses will tell you the correct order number~


Yep, Turn the headlights on while the truck is running, If the headlights flicker or get brighter as the RPM's go up, then it's definitely the voltage regulator. I've changed out mine on my '79 F-250 a few times already over the years, Ofcourse I've had the truck since new, LOL !!! Kenny/MrBlueOval

1 out of 1 people think this is helpful.
Martin Hamel

If you want to know what's draining your battery when your truck is sitting, plug a voltmeter or multimeter in series with your battery. Unplug the negative side of it, then connect your voltmeter between the negative side of the battery and the cable. Without turning the accessories on, start pulling fuses. In the Amp mode, you'll find right away what's drawing power from your battery... Good luck!!

1 out of 1 people think this is helpful.

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