Umm Bad Alternator?
Senior Member
Joined: Jul 2004
Posts: 5,155
Likes: 0
From: Eau Claire, WI
Vehicle: 97 Tib
If the car was running and you disconnected the battery and it stayed running, then your alternator is fine.
Your problem sounds like ..
1. a bad case of corrosion. Use a mixture of baking soda+water and scrub with a toothbrush or battery terminal cleaner (make sure to scrub the insides of the terminals (rings) too). Then, you go to the parts store and buy some WHITE grease, smear that stuff all over the terminals and posts and be generous about it, that should stop corrosion in the future.
or
2. a bad battery. get a new one. fing02.gif
keep in mind if your terminals are very corroded, then you may still have problems even on a new battery.
Your problem sounds like ..
1. a bad case of corrosion. Use a mixture of baking soda+water and scrub with a toothbrush or battery terminal cleaner (make sure to scrub the insides of the terminals (rings) too). Then, you go to the parts store and buy some WHITE grease, smear that stuff all over the terminals and posts and be generous about it, that should stop corrosion in the future.
or
2. a bad battery. get a new one. fing02.gif
keep in mind if your terminals are very corroded, then you may still have problems even on a new battery.
Senior Member
Joined: Sep 2009
Posts: 4,185
Likes: 0
Vehicle: Elantra HD / 2007
1. check battery voltage when engine is off and everything in car is off too. Should be a bit higher than 12V.
check voltage when engine is off, headlights on, blower, etc. , should not go lower then 11V.
then try checking voltage while turning on starter (should not get lower then 11 - i think).
If it's not - probably you have faulty battery.
2. check voltage when car is running it should be about 14V (if not - probably faulty alternator or voltage regulator).
3. you can also check power drain.
turn all everything, disconnect 1 terminal and use ampermeter between disconnected terminal and disconnected wire. It should be close to 0, could be 0.08A for example.
check voltage when engine is off, headlights on, blower, etc. , should not go lower then 11V.
then try checking voltage while turning on starter (should not get lower then 11 - i think).
If it's not - probably you have faulty battery.
2. check voltage when car is running it should be about 14V (if not - probably faulty alternator or voltage regulator).
3. you can also check power drain.
turn all everything, disconnect 1 terminal and use ampermeter between disconnected terminal and disconnected wire. It should be close to 0, could be 0.08A for example.