Battery or alternator Options

[iankarr]

Hi guys

My "new" 914 has been having trouble turning over, even when cold. I found out the PO hadn't changed the battery in 8 years, so I headed to the store to pick a new one up. about 100 yards from the store the car died cold. No juice at all. I did the push of shame:).

Put a new battery in and was able to start the car and drive home. Now I'm wondering if I may have an alternator issue. When the car is off, my multimeter on the battery terminals reads 12.0V. When I start the car it goes up to 13.5V. Does that mean the charging circuit is working? Is there a more conclusive test?

FYI, the "gen" light never goes on while driving, but does illuminate when the key is turned to the acc position, along with the oil indicator.

Thanks!

[914itis]

I think it's all normal , I don't se e an issue . Unless I am missing something. You changed the battery and it started . Battery life is 5 to 5 years .

[dangrouche]

13.5 is correct voltage at the battery terminals when running. the idiot light you described is also correctly working. since this car is new to you, you may want to check your ground points for good connection:
1. engine compartment: battery to chassis
2. beneath rear trunk: ground strap braid, transmission to rear trunk
3. engine compartment: beneath relay board
4. passenger compartment: above fuse panel
5. engine compartment: top of engine case beneath trunk lock
6. front trunk: headlight grounds

I have an Optima that is 8 years old and I regularly put it on a trickle charger. A new battery really makes a difference. I generally use my Harbor Freight battery load test meter before I go right out and buy a new battery.

use this google search engine for all your 914 inquiries:

https://cse.google.com/cse/home?cx=00240834...772:ajvfxschcgc

[iankarr]

Thanks. The part that concerns me is that the car totally died. I would usually expect a weak battery to keep it from starting, and that a running car would keep running even if the battery is weak. Unless maybe that battery was totally shot

[SLITS]

Car will die below about 10 volts. Not enough juice to run the fuel pump, ignition and whatever else you have on.

I say 10 volts because that's what my gauge read when the car died. Alternator pulley sheared off. Was running on battery alone ... made about 250 miles before it quit.

[Dave_Darling]

It was 9V for me. Stepped on the brakes, the brake lights lit up, and pulled the system voltage down from ~10V to ~9V. I conjecture that was too low for the fuel injection computer to run, so it died.

The alternator was bad--I knew that, but tried to drive it home anyway. Almost made it, too.

--DD

[falcor75]

Is there an earth cable in the engine between engine and chassis? I've never seen that....?

[Dave_Darling]

If there is, it was added by someone. The ground path for everything grounded to the engine is: Through the crankcase to the transmission case, through the transmission case to the ground strap, through the strap to the bottom of the trunk floor, through the chassis to the battery ground strap, and through there to the battery ground post.

--DD

[Spoke]

When the car is off, my multimeter on the battery terminals reads 12.0V. When I start the car it goes up to 13.5V. Does that mean the charging circuit is working? Is there a more conclusive test?

12.0V for a battery at rest is low. It should read 12.6V or so. Seems like something is discharging your battery.

13.5V as mentioned is ok for the charging system.