quick questioncar

[jimc347]

i put a brand new battary in my car. starts runs for 5mins then battary[ is dead. what to check???????

 

[HISSIN50]

A new battery does not mean a charged (or even good) battery.

But do you have alternator output? On a car that is off, put your DMM on the battery terminals. Look for ~12.6 volts. Once started up, look for 13.5+ volts. If you are below 12.6 volts while the car is running, you are running off the battery.

Good luck.

 

[jaymac]

alternator.
Good luck.

 

[srothfuss]

If the alternator proves to be good, you could have a bad DIODE. This little device prevents the battery from being drained when the car is off.

 

[jaymac]

also, make sure no loose wiring connections or wires are present. I had a wire that was not seated all the way in the harness for the alt., and the battery would die within seconds. It didn't look loose, but it was....

 

[jimc347]

okay thanks alot

 

[CoupedUp]

If the alternator proves to be good, you could still have a bad DIODE. This little device prevents the battery from being drained when the car is off.

Just to expand on what he's talking about ...
A diode is a one-way valve for electricity.
The diode only allows current to flow in one direction.
A/C = alternating current
D/C = direct current
An alternator generates alternating current (a/c).
The diodes in the alternator "turn" the a/c into d/c to recharge the battery, because a battery is a D/C circuit power source.

Like srothfuss said, if a single diode or group of diodes (rectifier) is shot it can discharge your battery quick enough. A fully charged battery usually takes longer than 5 minutes though.