'91 Ford F150....would an alternator keep draining the battery and making it not start? And if so would you be able to keep jump starting it?
2006-06-29 03:21:38 · 16 answers · asked by Mz_AmanDA 4 in Cars & Transportation ➔ Maintenance & Repairs
My 1989 Ford 5.0 had the alternator slowly fail over several weeks. At first the battery just drained overnight so I thought I had a short in the electrical system. Then I needed a couple of jump starts. Eventually the alternator stopped charging completely.
Charge up the battery and measure the voltage. It should be 12 or 13 volts. Then start the truck and measure the battery voltage. If it is 13 or 14 volts then the alternator is charging. If the battery voltage drops with the engine running then the alternator is bad.
To test to see if the alternator is slowly failing: With the engine off measure the current flow between the positive battery terminal and postive battery cable. Then disconnect the alternator wiring harness and see if the current draw goes down. The only thing draining the battery with the truck off should be low amp things like the clock, etc. If the alternator is drawing curent then it has a bad diode or something and is draining the battery.
Your alternator has the voltage regulator built in and costs about $90 to replace.
2006-06-29 03:37:49 · answer #1 · answered by idaho98076 4 · 5⤊ 0⤋
If an alternator is bad it can still produce enough electricity to keep an engine running. It takes aprroximately 8 or more volts to start a well tuned engine, but very low voltage to keep it running. A jumped battery can run an engine for a good half hour, not 1-2 min., even if it has a weak or bad cell. Best bet is have the alternator tested at a test station(service center or parts store that does free tests). they can also test your battery & the rest of the electrical system if needed.
2006-06-29 13:08:14 · answer #2 · answered by No! Freedom of speech is abused 2 · 0⤊ 0⤋
Yes. A bad alternator COULD drain a battery. However it's doubtfull that it is draining the battery. A simple way to see if it is the problem is to use a volt meter while it's running to test the battery voltage. It should be over 12.7 volts DC.
If it is bad, you've probably burned one of the rectifiers (basicaly a big diode) that changes the voltage from AC to DC.
An Alternator technicaly generates an AC current and the rectifier changes the voltage to Direct Current. If you have a bad rectifier, the battery current is allowed to go backwards thru the alternator to ground.
2006-06-29 10:32:45 · answer #3 · answered by Mr. KnowItAll 7 · 0⤊ 0⤋
Take off negative terminal so that if you accidently touch a metal object it will not arc, and possibly cause an explosion of hydrogen gas that is present when a battery is low on charge. If it keeps running, then it is not the battery. Find out if you have an external voltage regulator.Take the alternator to a place that can load test it. You can have it rebuilt if you can find knowledgable people to do it for you. Also sometimes your starter can draw on the battery enough so that if you take several short trips,starting and shutting off the engine and restarting it, your alternator does not have enough time to recharge the battery correctly.
2006-06-29 10:52:12 · answer #4 · answered by ccf0005701 2 · 0⤊ 1⤋
To test the alternator, start the truck. Loosen and remove the positive (+) cable from the battery. If the truck dies, it's a bad alternator. If the truck stays running, it's something else.
Jumping the truck will not hurt the battery, but running the truck with a bad alternator for a long time can damage the battery.
2006-06-29 10:27:08 · answer #5 · answered by wildbill05733 6 · 0⤊ 1⤋
Measure the voltage of the battery with the truck running, it should be above 13V. If not, the battery is not charging. The other option is to remove the alternator, bring it to a parts shop and have them test it. If the battery is draining with the truck not running, you have a ground somewhere. Hope this helps.
2006-06-29 10:29:04 · answer #6 · answered by Tim D 1 · 0⤊ 0⤋
Absolutly. My car won't start RIGHT NOW because my bad alternator has drained the battery. I had to get 3 jump starts just to make it home from a 3 mile radius. My advice, get an alternater, FAST. I'm making arrangments now.
2006-06-29 10:26:59 · answer #7 · answered by morethanacuteface 1 · 0⤊ 0⤋
The alternator is the generator of electricity. If it is not working the battery will be constantly flat the wipers would be really slow and the lights dim. The turn signals would flash really slow and the engine would misfire and stall. Jump starting wouldn't get you very far either. Jules, auto tech and lecturer. Australia.
2006-06-29 10:28:12 · answer #8 · answered by Jules G 6 · 0⤊ 0⤋
alternator does not "drain" battery....the opposite happens. here's a good test to see if your alternator isn't working: get the vehicle started. remove battery. if engine dies, then alternator is bad. if it conitnues to run, yet in the morning, or few hours the motor won't start, then you have something electrical draining the battery...or simply a bad battery that needs maintenence or replacing.
2006-06-29 10:26:31 · answer #9 · answered by Ryan 4 · 0⤊ 0⤋
The alternator is what keeps your battery at a certain charge while its running, so if it's no charging you battery, then that' s a problem.
2006-06-29 10:25:52 · answer #10 · answered by Amanda 4 · 0⤊ 0⤋