I have a 78Z. When I go to start it in the morning after sitting for a couple days the battery is dead. It jumps with ease and the volt meter is reading 16volts. I let the car run for about an hour. All guages where reading fine. I reveved the motor and pulled it into the garage. the volt meter dropped to 121/2 volts and the charge light was on. I rev the motor with no change. I am thinking i my have a couple different issues. The first is I think I have a short that is drainng the battery. The second is I think the brushes in the alternator are starting to go and when I rev the motor the brushes are failing. The alternator is only 2 years old but is a remanufactured one. i have only put about 7k on the car in the past 2 years. Most of that the first year. The 2nd year I may have driven it only 500 miles.

I am looking for any input to helpme out.

Thanks
Shane

 

Test battery
1. Remove battery and charge it with a plug in battery charger overnight. (slow charge) Then unplug all wires and let it set for 2 days. Check voltage. If its low then of course the battery is bad. It loses charge with nothing plugged in. If its good, then put it back in the car and see if it starts the car. If it does, then something is draining the battery in the car. (probably)

2. Replace your battery cables. A lot of the time this is a cause for charging and starting problems. Maybe even add a second or third small ground strap to the frame and to the engine head. The main ground usually goes right to the starter. (which is basically bolted to part of the engine block.

You have an amp meter which is difficult to get any good info from. They tell me nothing. If you have an aftermarket volt meter or even a shop voltmeter, wire it in temporarily and set it in the passenger seat. See that when the car is off the battery reads 12 or 12.5 volts. Then when you crank it it should read 10 volts or so, but as soon as the engine starts if the alternator is putting out good current the voltmeter should read 14.4 volts with all lights and electrical accesories off.

When your engine is running, is the BATT light on? (on the dash)

get back to us on what you've done for any additional suggestions.

 

I tested the Battery and she is at 11.97 VDC according to my Fluke meter. I installed a dual amp fuse block. I ran 1 main power line into the block. It then splits into to 2 40amp fused links. I hooked the 2 main wires that are attached to the fire wall to this. I mounted the box to the firewall next to the battery. ( While I was at it I shined my dip stick).
I started the Z and checked the voltage. The battery was sitting at 14.23 and so was the Alternator. So i am guesssing everything is good there. I also tested the battery after shutting the Z off. It tested at 11.97 volts.i plan on checking this every hour or so. it is 21 degrees out in the garage so i am freaking cold.

I will keep you posted.

 

Your battery should be 12.6V fully charged. 11.97 is quite dead. You probably need a new battery.
-jeremy-