bad battery or bad altenator?

Question

car seems to have power but wont start,starts right away with a jump but when it is turned off won't start again . sometimes will start on own drive it and turn it off then won't start after awile of sitting starts again. the other day while driving the radio lost power headlights became dim after a couple of minutes radio came back on and lights returned to normal.
there is a fuse that constantly blows(dash instruments and gauges) anyone have any ideas thanks

Answer 1

When's the last time you had your battery replaced? If it was less than a year, I'd venture a guess that it's a bad alternator.

Answer 2

Here is the test procedure for determining battery or alternator problem after requiring a jump start. Note, requires a voltmeter [$3.50 at Harbor Freight]
1] Check battery voltage on non-start vehicle. Will probably be under 12V. Verify good clean connections, look for cracked corroded or loose terminals.
2] Jump start. Note, always have the jumper vehicle running when performing a jump start, sounds basic but I actually had a friend who argued it should not, meaning he would be jumping with less voltage & could strand both vehicles.
3] With jumper cables removed, check voltage at battery. It should be 12.8V to 13.7V. If below 12.8V the alternator or voltage regulator are suspect. If in the range, the battery is either dead, low on water or in need of a full charge. If over 14.7V the voltage regulator is not functioning properly.
4] Failing those problems, with the vehicle shut off & the doors closed, disconnect the battery ground cable, put a 12V test light between the battery negative & a known good ground. If it lights, something, like an interior or glovebox lamp, is staying on. Remove fuses 1 at a time to find the problem circuit.

When chasing an intermittent blown fuse problem it is often easiest to remove the fuse & replace it with a circuit breaker of the same amperage rating. If need be make up a small harness to either clip or plug into the space vacated by the fuse. Then, with the circuit live, try to wiggle individual wires or components [like the radio] if the circuit breaker clicks, you’ve found the problem.

Answer 3

First I would look for the short causing the fuse to blow.........Added accessories usually does this, a wire being cut by metal contact?
As for no start, but will with jumper...........Low battery........could be voltage regulator, have you cleaned the battery cables? Remove and clean clamps and posts on battery.
With engine running battery voltage should peek out at 14.8 volts nothing turned on. Some will normally run as high as 18 volts hot. Anything below 13 volts, you have a problem.
With some alternators you can feed the regulator terminal with battery power and determine if it's a regulator problem, of Alternator. Caution a good alternator can be driven to over a hundred volts @ 100 amps. Yes! You can be killed!

Answer 4

Could be either. Check the water level in the battery (if not a no-maintenance type - lift the two covers (three holes under each) off the openings (carefully -there's acid residue in there) and fill to just below top with pure water). If it isn't that, listen when you crank car to start, if you're hearing clicking noises, the alternator's shot. If it whines while running it could be a loose fanbelt, causing the alternator to work less efficiently. Good luck.

Answer 5

The cause could be bad alternator, but I believe you have more than one cause-bad earth could also affect the charging circuit.
Best is to do complete electrical check of the charging systtem for short circuit or voltage drop at both ground and positive sides. If possible seek help from a competent electrician who understand principle of auto electric.

Goodluck!

Answer 6

You have a short circut in the circut that keeps popping breakers. It sounds like a bare wire is touching somewhere. Is your radio a stock unit or is it something that was added after the car was bought? If it is not a stock unit, I'd look at all of the connections to the radio for a bare wire. If it is stock your best bet is to tell a mechanic about it and let them find it.
Good luck-electrical searches suck!

Answer 7

start the vehicle, jump start...or whatever. While the vehicle is running, disconnect the battery. If the vehicle runs, its the battery, if it dies, its the alternator. The alternator is what keeps the engine running...the battery is used to supply power to the alternator to start the vehicle.

Answer 8

ARE THE BATTERY CABLES AND TERMINALS IN GOOD CONDITION...ARE THEY TIGHT WITH NO CORROSSION(BUILD UP )? YOU MIGHT HAVE A BAD CABLE GOING FROM THE ALTERNATOR TO THE BATTERY( SOMETIMES THEY BURN FROM INSIDE THE PLASTIC COATING. AND ALSO CHECK THE TERMINAL OF THE BATTERY...SOMETIMES WE BANG ON THEM AND CRACK THE TERMINALS ON THE BATTERY BY BANGING TO HARD

Answer 9

alternator for sure unless it's just the belt, which has drained the battery, you might need both if it blew the cells in the battery.

Answer 10

can be bad altenator .