74 2.0 FI with console voltage gauge, shows 13+ volts running with no lights on. Turning on parking lights or stepping on the brake drops it to about 12.2. Turning on headlights drops it further to just below 12. Fog lights have no effect (they are working) but turn signals will drop it to 11 with headlights on. Brakes with headlights on also drops it to 11 volts. Battery (Red Top) shows 12.5 volts with engine off after a good run.

Before someone says: "Did you read the threads here on this?" Yes, I have, and the same conditions draw responses ranging from "that's normal" to "your regulator/aternator/phisoginator is about to fail", so they leave me right where I started.

I have cleaned the grounds in the front fenders right by the headlight motors, with no effect.

So, three dumb questions:

1. what's the best way to check the voltage being sent to the battery
2. where is the ground connection to the body for the tailights,
3. am I worrying about nothing?

Happy Thanksgiving to all and thanks for any advice.

Check the actuall battery voltage at the battery.

The tail light ground is on the side wall below the relay board.

The stock voltage gauge is almost useless.

The console gauge is, like horoscopes and 911 oil level gauges, 'for entertainment purposes only.'


At the battery posts.

can't help you on that one, sorry...

Probably. Where the console voltmeter connects, it cannot be reliable, except when it shows '0' with the ignition off...

I should have clarified that the battery voltage of 12.5 was measured at the battery, not taken from the gauge.

This is caused by where the voltage reading is being taken. Off the harness from fuse S9 after the power is being applied to other loads.
Best place to monitor battery voltage is directly from the battery.
It is normal for this to happen on the 914 due to the place where the voltage is monitored, the voltage at S9, not the battery. Lots of "line loss/ IR drop" involved. If they had used larger wires, it wouldn't be so evident either.
Tom

Each cell of the battery is about 2.1 volts. A car battery has 6 cells. Your voltage at 12.5V is acceptable. Most alternators/regulators do not produce charging voltage below 1500rpm. At idle with all your loads turned on, you should see less than 12.5V. At >2000rpm you should see about 13.5-14.5V at the battery. The stock volt gauge is wired to see all the loads in the car. That's why you can turn on the blinkers and watch it bounce. If you want the stock gauge to be more "accurate", you would need dedicated power and ground wires from the battery 12gauge or larger.

At 12.5 volts at idle with everything on, yer fine. Best use I found for the stock gauge is to verify the brake lights and turn signals are working. No needle movement, and you have a failure!

I use mine to remind me that I've left the turn signal on, again.

Don't let your old voltage regulator fail & boil your battery.