98 ranger voltage never drops from 14.5

[Rob_p]

I’ve been reviving my old ranger and had what I thought was a drain issue, after 20 mins the drain would go from 350ma to 250ma so I assumed that was the issue because everything I’ve read says after 20 minutes it should completely drop to the 40ma area. but after waiting an hour it now drops to 40ma, so I assume that’s all fine. Now I notice no matter what with a brand new battery and alternator the voltage will never drop from 14.5 which is the high limit. I swapped alternator again and still the same thing. I’ve verified I’m getting battery voltage to the yellow wire and I am. if it were bad that’s the only reason it would stay in (charge mode) that I can think of. Any ideas? I’m at a loss.

 

[RonD]

Welcome to TRS

Yes, 14.5volt long term can cook your battery

What is battery voltage after sitting overnight or at least 4 hours?
New battery should be 12.8v
3 year old, 12.5v
5/6 year old 12.3v

12.2v or less can cause alternator's voltage regulator to stay high, battery is failing

Test if voltage regulator is working
Start engine
Test battery voltage
Then turn on all lights, heater fan to high
Voltage should drop and then come back up, if it just drops a bit and stays there, then voltage regulator is stuck

Then try raising RPMs while watching battery voltage, it should go up as RPMs go up and then if you hold RPMs at say 2,000, voltage should drop down to what it was before, regulator is not stuck

The voltage regulator sends 7-9volts to the brushes for rotor, this is what controls the AMP/Volt output from the alternator's 3 Fields
If its stuck at one voltage then turning on devices will increase AMP draw and lower voltage
And increasing RPM will increase AMPs so voltage goes up

Regulator is suppose to adjust the voltage to rotor to match amp draw, which I will called "Pushback"

Just after start up Pushback is low because battery was drained, so voltage regulator sends more volts to rotor
As battery is recharged Pushback goes up so regulator lower volts to rotor
When you turn on devices Pushback drops again, so regulator raise volts to rotor
In general the Pushback in a system should be about 1.1volts above battery volts after 5 minutes or so of engine running, so 13.4-13.9v
And it will go up to 2v above battery voltage just after start up, so 14.3 to 14.8v

 

[Rob_p]

After sitting it’s 12.8, I can’t turn the stuff on and watch for movement but last time I did it it went from 14.56 to 14.51. I’m at work for the night so I’ll check for raising or lowering of voltage with RPM. What externally from the regulator can cause this to happen? As of today this is three alternators in a week with the same exact issue.

 

[Rob_p]

So I just got home to be able to test, the regulator does appear to be regulating if you will. After a long drive and significant idling the voltage appears to drop out at 14.35 and stays there. If I turn on highbeams I can see the voltage drop to about 14.2 and then very quickly jumps back to 14.35. I also once again verified that the yellow wire is receiving battery voltage as well. After sitting 12 hours the battery was right at 12.83 V.

 

[RonD]

Were they all the same brand of alternators?

 

[MikeG]

And by the way it wouldn't hurt to check your multi-meter. When the battery starts to go on that..... it can affect the readings. If it has an AC mode then use to to check the wall current in your house, should be close to 120 volts.

 

[Rob_p]

Were they all the same brand of alternators?

Yes, motor craft from oreilly

And by the way it wouldn't hurt to check your multi-meter. When the battery starts to go on that..... it can affect the readings. If it has an AC mode then use to to check the wall current in your house, should be close to 120 volts.

I have another tester, I’ll try it in a bit.

 

[RonD]

12.8v at rest battery voltage and engine running 14.3v after 10min or so is only a 1.5v difference so close to the 1.1v and its not the full 2.0v quick charge

So maybe thats spec for the 1998 charging system

 

[Rob_p]

Fair enough, anywhere I can look up the actual documented specs to know for sure? Also it took a long time to drop to the 14.3 so that kind of makes me nervous but I guess I’ll just let it ride and see what happens. Thanks for the help!

 

[RonD]

You can check with Battery Maker and see what their specs are for maintenance charge voltage, and whats "too high" long term
The 14.0-14.8volts won't hurt any of the vehicle equipment, only concern is overcharging battery and shortening its life

 

[4x4junkie]

So I just got home to be able to test, the regulator does appear to be regulating if you will. After a long drive and significant idling the voltage appears to drop out at 14.35 and stays there. If I turn on highbeams I can see the voltage drop to about 14.2 and then very quickly jumps back to 14.35. I also once again verified that the yellow wire is receiving battery voltage as well. After sitting 12 hours the battery was right at 12.83 V.

Completely and 100% entirely normal.

When the alternator (engine) is cold, it's volt regulator purposely boosts up the voltage a bit for about 10-20 minutes until everything is warmed up (the amount of voltage boost is proportional with outside temperature). This is because a cold battery needs more voltage to charge properly than a warm battery.
On a very cold morning (32°F or less) it's actually normal to see voltage of 15V or more for several minutes. In more moderate weather and after driving for a bit, the voltage should gradually drop, finally ending up in the range of 14.25-14.4 volts (as you found).

 

[Rob_p]

Completely and 100% entirely normal.

When the alternator (engine) is cold, it's volt regulator purposely boosts up the voltage a bit for about 10-20 minutes until everything is warmed up (the amount of voltage boost is proportional with outside temperature). This is because a cold battery needs more voltage to charge properly than a warm battery.
On a very cold morning (32°F or less) it's actually normal to see voltage of 15V or more for several minutes. In more moderate weather and after driving for a bit, the voltage should gradually drop, finally ending up in the range of 14.25-14.4 volts (as you found).

Awesome thanks, everything I kept reading on multiple sites kept saying after the drop you shouldn’t be over 14 or you’ll cook your battery. I appreciate it! Glad to be done with this.

 

[4x4junkie]

That was probably before "maintenance-free" batteries that use either lead-calcium, or pure-lead plate construction became the norm.
Old-school "low-maintenance" batteries (having lead-antimony plates) would evaporate their water rather quickly if charged at much over 14V in a hot underhood environment (they are now mostly obsolete for underhood use).