98 Taurus Voltage Regulation - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

MiniMaxMan · 03-16-2007, 08:33

In the post about my smoking alternator, I posted that the output from the alternator seems too high. The battery is reading about 14.8 volts with the engine running.

Does anyone know how the voltage regulation works? Could there be a trim pot somewhere to adjust? I just put in another new alternator. The little 3 terminal plastic module on the alternator has OEM Ford markings. The last rebuilt alternator that burned up had a plain white plastic module.

If there a way to set this or adjust it, I would like to drop the voltage to about 14.0-14.2 volts.

SHOZ123 · 03-16-2007, 10:21

Non adjustable. The regulator should be outputting 14.6V but they usually are under that. Is the battery gassing excessively when at that voltage? Maybe the meter is not quite accurate.

MiniMaxMan · 03-16-2007, 13:56

I'm not sure if the battery is gassing yet. It's only a few weeks old. My son doesn't drive the car much, mainly to school. He only put 1200 miles on it in 3-1/2 months. I used my Fluke meter to measure the battery at 14.8 volts, the same meter reads my Nissan at 14.05 volts. The battery is getting about 9 amps of charge current. That seems too high just to keep it charged. When a lead-acid battery is fully charged at 14 volts, the charge current should only be an amp or two.

SHOZ123 · 03-17-2007, 00:36

Yes if the voltage is 14.8 and the amperage is 9 then either the battery is no good and gassing like crazy or the regulator is bad. What is the battery voltage after sitting for 24 hours of rest?

MiniMaxMan · 03-20-2007, 12:48

It's a brand new battery, 2 months old. I checked it while the neg cable was pulled for the alternator change. I think it was reading 12.6 volts.

**jwko** · 03-20-2007, 21:05

To me, 14.8 is within the norm and I would just drive it. I wouldnt worry about the 9 amps either. I tried to post on the other thread something I found that shows how the voltage will fluctuate but I guess no-one understood what I was meaning.

Other than that, go get a different alternator, battery or cables.

And I Quote:

Quote:

The exact charging voltage will vary according to the battery’s state of charge, the load on the vehicle’s electrical system and temperature. The lower the temperature the higher the charging voltage, and the higher the temperature the lower the charging voltage. The "normal" charging voltage on a typical application might be 13.9 to 15.1 volts at 77° F. But at 20° F below zero, the charging voltage might be 14.9 to 15.8 volts. On a hot engine on a hot day, the normal charging voltage might drop to 13.5 to 14.3 volts.

Charging amperage is another number that can reveal the condition of the alternator. With the engine idling and no load on the charging system (lights and all accessories off, and battery fully charged), the amperage output should be relatively low (typically less than 10 amps). With the headlights and heater blower fan on and the engine running at 2,000 rpm, the output should jump to a higher reading, typically 25 to 30 amps or more.

SHOZ123 · 03-20-2007, 23:29

A good indicator of battery condition is the minimum amperage from a 120V battery charger, not an ancient one, after the battery is fully charged.

Say after 12-18 hours and the charger set to the low limit the battery should only take <1A.

If you take an ohm reading of the battery then you can use ohm's law to figure out the battery's true peak voltage and amperage to keep it there.

**jwko** · 03-21-2007, 00:01

Ohm a battery, that sounds hazardous to a meter, or is it? Its been several years since I was in HVAC school (only took a semester) but seems like I was taught to measure ohm's you actually used the voltage of the meter to test, you wouldnt meausre a live circuit.

If the car was at idle, alternator's output was 14.8v, amperage was at 9 wouldnt that be considered normal with the fuel pump,computer and all the sensors are drawing current?

quote: The battery is getting about 9 amps of charge current. That seems too high just to keep it charged. When a lead-acid battery is fully charged at 14 volts, the charge current should only be an amp or two.

Thats fine on a battery charger, but if the car is running then there is a drain on the battery therefor amps will be higher.

Thats all I know to say about this thread, drive it, its fine