I was coming home from the boat ramp yesterday and all of a sudden the radio turns off, so i look down and see the battery light come on, then the abs light. Slowly my gauges all died and the truck started to lose power i had nowhere to get off so i floored it and tried to get as far as i could till i barely made it into a parking lot flooring it creeping to a halt. I ended up getting home using my boat starter battery and once i got home i watched my gauge and as i turned things on (lights,radio,etc) the gauge would go a little bit lower each time. With everything on the battery gauge is a little below halfway. Could this be a battery or an alternator? How can i go about figuring which one it is?

 

Will it jump start? If so, do it and go to a parts store, they can load test the battery and alternator in the parking lot, free of charge.

If it won't jump or it dies right away, pull the battery and take it to the store, have them charge and test it. If it tests bad, buy a new one, if it tests good, reinstall it. Then start it and take it to the store for an alternator test, unless you want to pull the alternator and take it in for a bench test.

 

Can they test the alternator while its on the truck? Ive got my boat battery in the truck right now and its working and i put my truck battery on the charger

 

They said my battery is good and not sure about alternator im using my boat battery and they said its staying at 11.57vlts so not a normal 13-14 but its not dropping ethier and i would think this battery would be dead by now if alternator is not working right, he said check fuses, which could it be??

 

Sounds like the voltage regulator on the alternator is crapping out

 

My local Autozone's handheld parking lot tester can test both the battery and alternator on the vehicle.

 

They did it but all it is, is a voltage meter how does that test my alternator??? im still using my boat starter battery and it hasnt died yet, they said my truck battery is good but i charged it up put it in my truck cranked it twice and it died... Im so confused its my 2nd full day using the boat battery shouldnt it be dead by now

 

The handheld tester at the Autozone here is a lot more than just a voltmeter. It's a load tester.

Sounds like they don't even know how to load test a battery either. Go find a parts store that knows what they are doing.

 

Your alternator is not charging the battery. Either it is bad or one of it's external electrical component (field fuse, megafuse, harness) has failed.

Use an external charger to fully re-charge any battery before running the engine. With a fully re-charged and serviceable battery and doing everything possible to minimize electrical draw, you can usually get 20-30 miles out of the battery before it's discharged.

 

I did use an external charger to charge my truck battery they said it was at 89 percent i started the truck let it run for 2-3 mins turned it off tried to crank it and it would not crank. The marine battery im using now is a starter not a deep cycle and i have used it for 2 whole days and i cranked my truck on and off 5 times in a row with no problem it sounds like the batterys the problem even though they said its still good, when using the boat battery the gauge fluctuates a little bit but it typically stays higher than half way, also the battery light randomly comes on then goes off, im going to try and get it load tested but with work and school all day everyday its hard

 

okay i thought the problem was fixed but i guess not, went to interstate and they gave me a brand new battery under warranty thank goodness but that was two days ago and im driving through my apartment complex and it seems like lights are a little dim so im watching the battery gauge and its starting to drop i park it shut off my truck try to crank it and it wont crank. should i try and replace voltage regulator first before alternator? can anyone help me out with where exactly the voltage regulator is in my truck 04 f150 2wd 4.6l

 

There is no separate voltage regulator, it's part of the alternator.

Again - GO GET THE ALTERNATOR LOAD TESTED.

 

Load test the alternator and also check the wire between the alternator and battery, Ohm test it. There is a fuse-able link in between if I remember right. I don't have my truck right now to double check.

 

The alternator in an 04 F150 is controlled by the PCM.

Be careful what you're blindly mucking around with lest you really screw things up even worse.

 

How about start the truck take a volt meter set to dc and see if battery is getting charged. If it is getting charged there should be a reading of at min 13 to 14 max. maybe a little over 14. If you only get like 12 or below 13 you need to look at alt.

You should be able to take it to autozone and have alt tested. Hopefully by the time you read this you have it fixed.