What voltage should a battery drop to when cranking?

You can test for proper cranking voltage with a voltmeter while—you guessed it—cranking the engine. The several hundred amperes of current the starter motor draws should pull the battery voltage down to a normal 9 to 10 volts.

What should a 12v battery read under load?

A healthy 12 volt motorcycle battery should maintain a range from 9.5 – 10.5 volts under the load, for a good 30 seconds straight. Batteries with open cells may read fully charged in idle, but they fail under a load test.

What should the voltage drop when cranking a BBC starter?

I found that a bbc starter will use about 300 amps. with 2 gauge cable at 18 feet I should expect 18% voltage drop. ie 12.8 should show about 10.496 while cranking, which is all well and good. at the relay for the ignition, its 12.77 at rest, 9.5 cranking. alternator is the same thing. 12.77, 9.5 while cranking.

Why does the battery voltage drop when cranking?

You will see a voltage drop in almost all cases “WHILE CRANKING” The amount of drop is a factor of the quality of the battery you are using. 11.7 to 9 volt is 25% of the battery capacity. Cheep bargain batteries are prone to this condition.

What should the voltage drop be on a car starter?

Either post type, crank the engine. Should get less that 0.1 volts. Test the negative circuit with your voltmeter from the battery negative post to the engine block and crank the engine. Should get less than 0.5 volts, but really around 0.2 to 0.3 volts is normal.

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 should my PCM read when the engine is off?

Reconnect any loose wires if necessary. If your PCM has experienced corrosion, you’ll have to skip to step 5 to see if it’s failed. While you’re under the hood, use your multimeter to ensure that your battery has a full charge. It should read at least 12.6 volts with the engine off, or 13.7 volts with the engine running.

What are the symptoms of a PCM failure?

So before we talk about how to test a PCM, here are some common symptoms of a PCM failure. There are other things that could be causing these symptoms. For example, poorly-inflated tires can cause a drop in gas mileage, and hard starting can be caused by a weak battery or failing starter.

Can a bad PCM be a good PCM?

You are quickly getting to the point where a bad PCM is the only reasonable conclusion. So unless there’s a weak power or ground that is good enough to light a computer safe test light but not good enough to power the PCM. While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)?

What voltage should a battery drop to when cranking?