1971 350 base motor.No air or power steering
OK one night after riding home with head lights about 1 hour shut car off then got back in it and battery was dead. Did not look at volt gauge at all during ride home. Charged battery to get car started and put in garage.
Put voltmeter on battery after trickel charger turn to green and voltage read 12.8 volts. Started car and volts went up to 14.2. Turned on lights and wipers and radio and still holding 14 volts.
Next trip out early morning turning lights on and volt gauge was going up then down all the time lights were on .
Pulled alternator and took to parts house and it test bad for voltage. Purchased new unit installed it.
Check battery with engine off 13.6 volts. Started car and 14.6 looked at gauge and gauge went to past middle 0 then into plus range half way then back to just at zero.
In the past my guage was always barley past center 0 towards plus reading.
Now without lights off its is there but with lights on it goes into the negative.
Check battery without car off 12.67 volts car on 14.6 then after lights on went down to 14.0 stayed there 10 min. with engine ideling at 800 RPM. At 1200 RPM would go up to 14.3.
Hope I am explaining myself correctly
Is this normal or do I have another problem.
Oh battery is 4 years old.
Never have a starting problem with it it always would crank it over.
Is the new Alternator seem to work correctly?
Do I need to replace battery?
Could my Volt gauge just be bad.
Or something eles?

 

You have some bad wiring or connection(s) in the charging circuit. The alternator is providing some charge, but not enough to keep up with electrical drain when lights, etc. are on. It could be a weak fuse link somewhere in the power wire side or some frayed/damaged ground strap/wire. The most common cause for that situation is a bad connection or wire on one of the battery terminals.

 

Tanks . Ground from battery to frame is new and is well cleaned same for positive side.
What else to look for?

 

As mentioned, check any fuse-links in the charging system power feed wiring plus all connections on power and ground wires between alternator and battery.

 

It sounds as if it is working fine. 4 years on a bat is enough, time for a new one. Volt guage seems good, but amp guage may be a little off or it could possibly be the old bat. Try the bat first since it is due anyway. Some amp gauges will read discharge at idle with a load on them and there is no problem. As you said it starts every time. I think you are fine

 

Thank you both for the info.

 

'71s don't have a volt gauge, they have an amp gauge that shows which way current is flowing. If it's on the + side the current is flowing to the battery.

 

4 years is the average life for batteries. Change it before you have to change it. Cheers.