Voltage Swing'n

[Tias63]

OK, in park, at idle, or idle in Drive the Voltage seems normal, about 13.8-14.0 volts. When I accelerate and hold my speed to traffic and running at normal RPM's the voltage swings up to about 15.5-15.8, then drops if I stop and idle. I'm not sure what the Alternator should be kicking out, but that upward swing does not seem normal.

 

[493 Mike]

You are correct, over 15 volts is too much. Check all the area ground connections and charging system power connections for defects, corrosion, and tightness. Rule that stuff out first.
Mike

 

[Ironbuilt]

What kind of gauge are you getting those numbers from? Are you sure the gauge is accurate?

 

[Ranger16]

What type of voltage regulator?

 

[Tias63]

What kind of gauge are you getting those numbers from? Are you sure the gauge is accurate?

Autometer, Analog, phantom

 

[Tias63]

What type of voltage regulator?

Stock style look, but electronic solid state internals

 

[Ironbuilt]

Autometer, Analog, phantom

I run those same Autometer Phantom gauges in my pickup, they are really accurate from my experience.

 

[66Satellite47]

Possibly a weak battery.

 

[Tias63]

You are correct, over 15 volts is too much. Check all the area ground connections and charging system power connections for defects, corrosion, and tightness. Rule that stuff out first.
Mike

I finally got around to checking all the grounds at both Stock style and electronic ign. volt regulators. I also used a Volt Meter to check everything and I have 15.3 coming out of the Alt. and at the Starter relay, bulk head, and battery I show 14.5-14.8. (running at 2000 rpm) Is that still too high?
I have a side step with the Alt. wire connected to the Starter Relay, then Starter relay to the bulk head connector.
Relay set up for headlights

 

[kiwigtx]

Everyone jumps in and says to "Check the grounds" frequently....but you should always check ALL connections first.

Live (positive) and negative connections (terminations) all matter.

The lower the voltage, the more a loose or tarnished/burnt connection will affect the system.

 

[Mopars & Missiles]

What kiwi said ^^^^^

Most likely you have a "voltage drop" in the regulator "reference" circuit. This is the wire that the voltage regulator uses to "monitor" the actual battery voltage. When it sees battery voltage drop, it ups the alternator output by increasing the field current.

Therefore, if your regulator sees a false "low battery voltage" due to a poor bulkhead connection (corrosion or loose fitting spade connectors, etc.) it will try to increase alternator output when it really shouldn't.

You're probably a volt too high at idle right now due to the same corrosion induced false reference voltage.

 

[Wietse]

I had a similar issue where the voltage was spiking up to 15 Volt, i could see it alarming on my Holley Sniper screen.
After checking i found that the positive terminal at the alternator (with internal regulator) was rusty, cleaned all connections back to bare metal.
Also the alternator ground wire had the same treatment and i have not seen the voltage come up that high any more.. 14.4-14.6 V
Worth checking on yours to see if that causes it?

 

[Tias63]

I'm still working this out. So I was reading and on the Head, by the intake is a spare bolt hole, and I read that this can be used for the battery ground. I was using the front left Intake Bolt, which also holds the return spring bracket. Well, some time ago I did the ol' silicone on the Intake bolts. I removed the grounding cable, cleaned a bare spot on the head, and secured the cable at that location. Cranked the car up and no more 15.0-15.8+ swings, I guess the Silicone was not allowing a solid contact. But I kind of have the reverse, now I'm only showing 12.2-12.4 volts when the car is running--lol. Battery is a Yellow Top fully charged @ 12.6 when the car is off.

 

[Mopars & Missiles]

I'm still working this out. So I was reading and on the Head, by the intake is a spare bolt hole, and I read that this can be used for the battery ground. I was using the front left Intake Bolt, which also holds the return spring bracket. Well, some time ago I did the ol' silicone on the Intake bolts. I removed the grounding cable, cleaned a bare spot on the head, and secured the cable at that location. Cranked the car up and no more 15.0-15.8+ swings, I guess the Silicone was not allowing a solid contact. But I kind of have the reverse, now I'm only showing 12.2-12.4 volts when the car is running--lol. Battery is a Yellow Top fully charged @ 12.6 when the car is off.

At that level, all you are seeing is the Battery voltage itself. The alternator is NOT charging at all. Continue to run it like that and you will see that voltage continue to slowly drop as the battery discharges.