Alternator voltage?

[RobV]

My dad and I were wondering why my voltmeter on the dash was reading 12 volts instead of 13.5 volts with the engine running. It's a Powermaster 100 AMP one wire Ford replacement alternator. So we started measuring voltages at different points. It measures 12 volts at the battery (engine running) and when I measured the voltage at the alternator post, it measured 22 volts. Is this normal?

Rob

[tpiini]

No way. It should read around 13.5 to 14.5 volts while spinning.

[ffindling]

Originally Posted by RobV

So we started measuring voltages at different points. It measures 12 volts at the battery (engine running) and when I measured the voltage at the alternator post, it measured 22 volts. Is this normal?

Rob

Most DC voltmeters won't read properly at the alternator output terminal
because the ripple content there is way too high. You need the capacitance
of the battery for the meter to read properly.


....Fred

[RobV]

Thanks Fred and tpiini, we didn't expect a problem. I don't think it's even possible for the alternator to put out 22 volts. I read on another web site that a voltage meter on the dash may read 12 volts while operating if the battery is charged or will be affected by the wiring (I guess they were refering to resistance) and may not ever read the 14 volts I expected it to read while running?

Rob

[trularin]

You have too much resistance between the alternator output and the battery. There is some kind of problem int he cable or your connection.

May I suggest you trace the output of the alternator back to the battery and see where it drops from 22 Volts to 12 Volts.

The difference is usually no more than 3 Volts from the front of the car to the rear. If there is, it is due to either too small of a wire used or a bad connection.

Just my opinion.

[1bad66]

I have a 80 amp 1 wire GM and had to use a 8 gauge wire to get good readings at the battery, the first wire I used was way to small.

[RobV]

I need to do some additional checking to see what the actual voltage drops are, but I have a "0" wire from the battery to the starter and run the alternator wire to the starter post. The wire from the alternator to the starter post is either 10 gauge or 8 gauge. I need to check. The length of the wire from the alternator to the starter is less than 6 feet. I do go through a relay to provide for a master disconnect. This is a Painless unit.

Rob

[tpiini]

It sounds like your system is set up just fine. You might want to check to be sure the disconnect switch has good contacts.

Tom

[RobV]

Thanks tpiini,

I think it's OK, but not sure. There does seem to be a draw on the battery if it sets for a week or so.