voltage drop

[terry]

hi folks, i'm having a problem with my 68 barracuda that after about 15 minutes of driving i notice that my volt gauge starts to very slowly drop from about 13.8 to 12.8 volts.now i may go out tomorrow and it will start again at 13.8. any idea's as to what may be the culprit?
terry

 

[KitCarlson]

Step 1. Verify your gauge with a multi-meter.

Step 2. Measure voltage drops with mult-meter.
Use a volt meter (multi-meter) to measure from (-) battery terminal to the engine where the (-) lead connects. If you find more than a few tenths a volt it could be the ground cable, or connection at the battery. Also check from the (+) terminal of the battery to the alternator output, again only a few tenths is good. Since it starts out at 13.8V, I assume your alternator is working. Now you can take this a step further and measure voltages on the interior side of the bulkhead, referenced to the (+) battery terminal. When you find about a one volt drop you may have found your problem.

Danger!!!! Keep meter leads and fingers away from moving objects like the fan and belts.

 

[RedFish]

Thats the norm for mine. Use up some cranking amps during starting and the alt' builds it back in the first few minutes of run.

 

[SGBARRACUDA]

I don't think you have a problem. When you start the car your starter draws alot of juice out of your battery. This why your gauge is showing 13.8. As your battery recharges it will drop down. If it didn't you'll cook your battery.

 

[terry]

thanks for the input. i am tending to lean towards sg reply. the battery that i had in the car was in it for 5 years plus another 5 years in another car. well just last week i put a new battery in the barracuda because the old one would not stay charged if i left the dome light on for ten minutes.
so as i see it the new battery may be the reason it doesn't charge as much.
terry

 

[69swinger340391]

Heat could be affecting the voltage regulator, causing it to maintain lower voltage as it is heated by the engine.