Voltage revisited

[sigtwenty]

Lets start fresh here.

Voltage drop at idle is 12.0 to 12.7.
Driving, when not over 100 outside is 13.6 and up.

Brand new alternator, and brand new battery. Headlights on or off dont matter, maybe a .1 volt but thats nothing to worry about.

This was same on last battery and alternator so I think by now we can rule this out.

No flickering lights. Only headlights dim when I increase idle a bit.

No error codes. No drivabilitiy issues. No starting issues.

[Timm]

Don't trust the OBC voltage - it can be miles out dependant on initial accuracy and which consumers are on.

[sigtwenty]

Voltage is from obd2 port. Obc is about .3v lower than obd2

Battery light never flickers or comes on. Even when I have seen the volts below 12v. It only goes below 12v when its over 100 degrees outside and after its been driven for a while.

[mtnbikerfred]

gounds. its fine. if you really want to know, measure AT the battery. if its low, check the enigine, body, and battery gounds.

[007008]

Use an Ohm meter to check the resistance between the block and the chassis.

[sigtwenty]

gounds. its fine. if you really want to know, measure AT the battery. if its low, check the enigine, body, and battery gounds.
Grounds would cause a flicker tho woundt they?




Use an Ohm meter to check the resistance between the block and the chassis.

Where on the block and chassis. And what is the resistance I should see

[007008]

A bad ground between the engine (cause thats where the alternator is) and the chassis will cause low voltage. The resistance to engine should be 0 ohms, Check between the ground post on the strut tower and anywhere on the engine or alt. that doesn't have paint on it.
On my VW the ground was so bad that I could get a ground jumper to spark.

- - - Updated - - -

Oh, also check for resistance from the negative batt post and the body. If I'm not mistaken the ground cable is attached to a stud right near the battery.

[sigtwenty]

A bad ground between the engine (cause thats where the alternator is) and the chassis will cause low voltage. The resistance to engine should be 0 ohms, Check between the ground post on the strut tower and anywhere on the engine or alt. that doesn't have paint on it.
On my VW the ground was so bad that I could get a ground jumper to spark.

- - - Updated - - -

Oh, also check for resistance from the negative batt post and the body. If I'm not mistaken the ground cable is attached to a stud right near the battery.
resistance is 0ohm

[007008]

I forgot to say, With the engine running.

[sigtwenty]

DOH! ok ill check again