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Can bad diodes in the alternator cause the battery to go dead when the car is off?
Wiki User
∙ 14y ago
Bad diodes in the alternator can cause the battery to go dead when the car is off. The diode bridge (six diodes) is directly connected to the battery, and is used to convert three phase delta AC from the alternator's stator to DC for the battery. Normally, if the engine is not running, the diodes are reverse biased and do not conduct current. If one of the high side diodes is shorted then the diode trio (another set of three diodes supplying the regulator/rotor) could conduct and drain the battery. Often, a diode failure is a short or an open. A short in a high side diode along with a short in a low side diode would result in high current from the battery, and that would probably blow the fusible link. An open would result in poor performance of the alternator.
Wiki User
∙ 14y ago
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Will a bad battery ruin a new alternator?
Yes, it can. A completely dead battery can blow the alternator diodes, at least in older systems - I am not so certain about newer systems, whether or not they are protected against this annoyance. In any case, the alternator is not generally designed to charge a battery from scratch, but just to keep it charged during normal use. The alternator will not be completely ruined, but it will not function until the diodes are replaced.
What problems does a bad alternator cause?
Dead battery, car will not start
Why does the battery in 1999 Mercury Grand Marquis go dead in a few hours after turning off motor and headlights?
Either the battery is very weak or the alternator has bad diodes .
Can you charge a dead battery by getting a second car that is running take the good battery out of the running car and put the dead battery into the running car as a means of charging it?
No, this will place a very heavy load on the alternator of the car and may result in burning out the diodes of the car charging the battery. You could easily ruin the alternator. Purchase a battery charger and charge the dead battery with that. Alternators are not made to charge dead batteries.
Would a bad alternator cause a battery to go dead?
either the alternator is dischargeing the battery or it is going flat just because its not getting re charged
Will a bad alternator cause new spark plugs to smoke?
Spark plugs don't smoke. A bad alternator would cause a dead battery.
Can running a new alternator on a half charged battery cause damage to either the battery new alternator voltage regulator etc?
Not likely, but running the engine with a dead battery can damage some alternators. Always fully charge the battery when installing an alternator.
How long do you run your car after a a car jump?
I assume you mean how long to charge the battery. You should never let the alternator charge a dead battery if possible. The alternator is designed to keep the battery charged but not to charge a dead battery. You put a strain on the alternator and it can cause a diode to burn out. Drive home and then put a battery charger on the battery to fully charge it.
What would cause a battery to drain in a 1989 mercury sable if it is not the power cords or alternator?
dead cell in the battery or something is on pulling power from the battery.
What would cause the battery to not charge even when the alternator tests good on a 93 Mercury Cougar?
the battery could have a dead cell, this could cause it to not charge. Have the battery tested to be sure.
Would a erg valve cause a dead battery?
no a egr valve would not make a dead battery. a bad alternator or maybe a bad connection post to battery would make it die ,
What could cause a 1999 Regal LS to occasionally have a dead battery the battery and alternator test good?
Bad connection, connections to battery aren't tight.
