Can a battery read 12v and still be bad?

Yes it can be bad if it’s output is 12 volts with no load and the engine not running… Load it down and watch the voltage drop… The starter is a good load to use for measuring the output under load.. Even a new battery voltage will drop with the starter running, but the battery should easily crank the car….

What is the reason for low output of voltage in an alternator?

Poor ground connections are an often-overlooked cause of low charging output and alternator failure. Check for voltage drops at the positive and negative battery cable connections, the alternator BAT+ power connection and the engine ground strap(s). Voltage drops on the negative side can cause overcharging.

How do I increase alternator output at idle?

The best way by far to obtain more power at lower engine speeds is to install an oversize alternator. The physically larger alternators produce more power at lower engine speeds and are much more reliable at higher outputs.

What should alternator voltage be at idle?

Most alternators that are charging properly should produce a voltage of about 13.8 to 14.2 volts at idle with the lights and accessories off. Always refer to the vehicle manufacturer’s specifications. Many Asian vehicles, for example, have higher charging voltages of around 15 volts.

Why does my battery gauge keep going up and down?

When the battery’s state of charge is low, the voltage is raised slightly to quickly put the charge back in. When the state of charge is high, the voltage is lowered slightly to prevent overcharging. If the vehicle has a voltmeter gauge, you may see the voltage move up or down. This is normal.

Where does the voltage meter in the dash show the battery?

The gauge is powered from the same circuit that provides switched 12VDC to all of the gauges, plus the AC components, safety switches and about everything that is powered up when the ignition switch is in the on position. It is a blue/white wire (according to this diagram) and comes from the fuse panel.

What should the dash gauge be right after start?

Right after start, at the alt or batteries (doesn’t mater) it will be low – the batteries are charging. Wait 5 min then measure. It should be 13.8 volts. If its 12 its too low. Alt neefs replaced. The dash gauge in these trucks is a joke. Huh, my answer when reading the post title was gonna be,,,, Stock gauges suck!

What’s the voltage on my boat dash gauge?

Voltage on my boat dash gauge is now running way high, like… I got 1973 Aristocraft boat with mercury 165hp inline 6 in it. Motor used to start so easy (not in water) and shifter functioned normal reverse and forward … read more Vocational, Technical or Tra…

What makes my voltage gauge read low when the engine is running?

Oluseun, with the engine running the gauge should measure the output of your alternator. The low voltage may be indicative of issues with your alternator. If you have one of those that shows the voltage without the engine running, then check your gauge for a bad resistor on the dash panel.

Why does the dash gauge switch from battery to alternator?

OK now that is starting to make sense. If the dash gauge switches over from reading battery voltage to alternator voltage after the engine starts, and there’s a diode between the alt. output and the battery, it would explain a lot. I will take readings at the alternator and let you know what I find.

What should the battery gauge read when the engine is not running?

A fully charged battery should read about 12.5 volts when the key is in the ignition and turned partially, but the car’s engine is not running. Step 2 Look at the voltmeter while the engine is running. Readings of 14 to 14.5 volts on the gauge when as a good sign.