How does a voltage drop test work on a car?

A voltage drop test will assess voltage losses at the battery, the alternator and the starter. 1) With the voltmeter connected to battery, and key and engine off, record a “base” voltage reading. (Your battery should have a minimum of 12.4 volts.)

What should the voltage be on a car charger?

The charging voltage should be at least 0.5 volt above base voltage reading. If not, excessive resistance could be present. Ensure the vehicle’s batteries have been tested and that the terminals have been cleaned and tightened.

How does a negative meter connect to a positive battery?

With all electrical loads off connect the meter, on a low amperes scale of about 1 ampere or so, in series with the battery negative post to ground. The positive meter lead connects to the car chassis, and negative meter lead to the negative post of the battery. A good electrical system battery drain

What’s the voltage regulator on my Silverado truck?

The truck now has 85,000 miles and on my way to go camping (about 125 mile trip one way) the voltage regulator dropped to around 11 or 12. Of course I panicked and found the nearest parts store to check for a bad alternator, they said all good no problems.

What makes my car voltage gauge read low?

As a vehicle slows, engine/generator RPM slows and the current (amperage) output of the generator may not be sufficient to supply the loads, the vehicle system voltage will drop and the lights will dim. Dimming of the lights is an indication that current is being pulled from the battery.

Why does my car voltage drop when idle?

• At idle, vehicle electrical loads may exceed the low speed current (amperage) output of the generator and when this happens the shortfall comes from the battery. This will result in a drop in the electrical system voltage as the battery delivers the additional electrical current to meet the demand.

What should voltage drop be on 12 volt battery?

12-volt system: 0.500 volts maximum voltage loss 24-volt system: 1.000 volts maximum voltage loss 2) Replace cables or repair circuits with excessive voltage loss. If the voltage drop exceeds specification, check for corrosion, frayed strands of wire, loose connections or a battery cable gauge that is too small.

What does a 5 Volt voltage drop mean?

But, before you condemn it, run a voltage drop test between the alternator and battery. GM typically runs a fusible link wire between them for overload protection and they can go bad, mimicking a bad alternator. A voltage drop of .25 volts or less is Ok and the alternator is bad. A voltage drop of .5 volts or more means the wire is bad.

Why does my voltage guage only show 9-10 volts?

My voltage guage usually points near the red mark at 9-10 volts. Batteries cranks the starter quickly and it does not seem to lack any electric power. Some times driving, it will raise to about 12 V, but never above, and the next minut point at 9 again.

Why does the battery gauge go back to 12 volts?

When your gauge read ~12volts and a new battery it went back to 15 volts, the old battery was overloading the alternator with an internal short. At one time I had a battery short bring it down to 9 volts and the computer went nuts. The engine back fired I just made it to a battery shop.

What’s the battery voltage on my GM 05?

My 05 does the same thing with a new alternator and battery. In the city it is around 14 volts, when I get on the highway it drops to 11-12 volts. If I put all 4 windows up at the same time the lights dim for a second and then the voltage goes up to 14-15 volts.

What’s the battery voltage on a Chevy Silverado?

As soon as I let go of the buttons it drops back to 11-12 the guage on my 2000 silverado and the 2002 stays at the 14 volt point with the engine running and very rarely moves off this reading. when the alternator regulator started to go the voltage would drop to just above 12 volts then jump back to 14volts.