1G 1g with Saturn Alt dropping voltage when hot

[monster24]

Wondering if anyone has any pointers or can recommend where I look into this issue. When car fires up it will show 14.3v all the time on my fuel tech but after some driving and things get warm seems that it drops well into the 13s. This is a brand new alt so wanting to make sure I’ve checked everything I should before swapping alts out. Also I see some conflicting information on wiring up the new connector. Should you use the factory wiring and connect to the new GM pigtail or do you just wire up a lead from 12v to the F pin on the GM pigtail?

 

[monster24]

Wondering if anyone has any pointers or can recommend where I look into this issue. When car fires up it will show 14.3v all the time on my fuel tech but after some driving and things get warm seems that it drops well into the 13s. This is a brand new alt so wanting to make sure I’ve checked everything I should before swapping alts out. Also I see some conflicting information on wiring up the new connector. Should you use the factory wiring and connect to the new GM pigtail or do you just wire up a lead from 12v to the F pin on the GM pigtail?

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[chrysler kid]

That’s typical alternator operation. After starting the car will increase voltage to charge the battery and as driven the voltage should drop to 13.4 ish to maintain the battery and run the car’s electrical system . What you want to see is that the alternator responds to voltage demands, that once the dip occurs it will respond to a situation, that if you turn the headlights on the voltage does not dip from the demand of current draw from the headlights. So if it’s 13.4 and you turn on the headlights and it dips to 13.2 and does not go back to 13.4 the alternator is not responding to the voltage draw

 

[miliman13]

That’s typical alternator operation. After starting the car will increase voltage to charge the battery and as driven the voltage should drop to 13.4 ish to maintain the battery and run the car’s electrical system . What you want to see is that the alternator responds to voltage demands, that once the dip occurs it will respond to a situation, that if you turn the headlights on the voltage does not dip from the demand of current draw from the headlights. So if it’s 13.4 and you turn on the headlights and it dips to 13.2 and does not go back to 13.4 the alternator is not responding to the voltage draw

Facts

 

[diambo4life]

Where is your 12V reference?

 

[monster24]

Where is your 12V reference?

My 12v reference is from my relay board

 

[monster24]

That’s typical alternator operation. After starting the car will increase voltage to charge the battery and as driven the voltage should drop to 13.4 ish to maintain the battery and run the car’s electrical system . What you want to see is that the alternator responds to voltage demands, that once the dip occurs it will respond to a situation, that if you turn the headlights on the voltage does not dip from the demand of current draw from the headlights. So if it’s 13.4 and you turn on the headlights and it dips to 13.2 and does not go back to 13.4 the alternator is not responding to the voltage draw

Im worried that the change in voltage is affecting my tune though

 

[miliman13]

Im worried that the change in voltage is affecting my tune though

Unlikely your ECU runs on 0-5v and so do the rest of the car - sensors.
the things that do run on 12v will still receive 12v, because your above 12v.

Do you have any data that suggest this is occurring? current and or prior for comparison.
Is anything wrong?

I get your just inquiring.

 

[monster24]

Unlikely your ECU runs on 0-5v and so do the rest of the car - sensors.
the things that do run on 12v will still receive 12v, because your above 12v.

Do you have any data that suggest this is occurring? current and or prior for comparison.
Is anything wrong?

I get your just inquiring.

I don't have any data on it as was hoping to investigate some more prior to working on the tune. Just was thinking I would ask before I go through all the work and the voltage varying ruining all the work put into a tune. I guess as long as it dips into the 12s everything should be fine.

 

[chrysler kid]

As long as it stays over 12.4 you should be ok. Always check your ground wires and make sure battery terminals have a clean connection

 

[CrazyDave]

Voltage drop test. Take DVOM from positive battery to Alt stud, should be almost 0 Volts. If there is resistance in the circuit it can lower the voltage, also a weak battery will cause low than normal voltage.