Voltage

[crytough]

Getting 15.6 volts from battery when car on. This seems way too high what do I look for as the problem ? 12.4 with of. Voltage regulator ? It's on a 1970 challenger

 

[Adam]

Yes, voltage regulator. If you haven’t already done so, I also recommend running a large wire directly from the alternator output stud to the battery positive terminal, or starter solenoid, to take most of the load off the bulkhead connector & ammeter.

You can run this wire from/ through the area by the horns, and up with the headlight harness, over to the battery.

Vintage Chrysler electrical repairs and updates

 

[crytough]

I already did the ammeter by-pass. Need to install voltmeter when I came across this problem. So you say the voltage regulator should be replaced

 

[Adam]

Yes, that is what I would do. The voltage regulator should be keeping the alternator output within specs, as the demand/load increases or decreases e.g. headlights, heater, etc.

 

[aussiemark]

If it smells like rotten eggs when running that will be the battery acid boiling inside the battery.

 

[AUSTA]

The regulator uses the case of the regulator to sense battery voltage if it hasn't got a good clean ground then the voltage will increase sometimes as far as 17 Volts.
Also check the Engine to vehicle frame ground strap the regulator ground should have continuity all the way back to the battery.

 

[crytough]

The regulator uses the case of the regulator to sense battery voltage if it hasn't got a good clean ground then the voltage will increase sometimes as far as 17 Volts.
Also check the Engine to vehicle frame ground strap the regulator ground should have continuity all the way back to the battery.

 

[crytough]

The regulator uses the case of the regulator to sense battery voltage if it hasn't got a good clean ground then the voltage will increase sometimes as far as 17 Volts.
Also check the Engine to vehicle frame ground strap the regulator ground should have continuity all the way back to the battery.

Thanks, just torched my starter relay, going to replace + volt reg.

 

[craigbred]

Hi, I had a similar problem. The screws or bolts that hold the regulator to the firewall may be rusty, or the threads in the firewall rusty. I ended up adding a small ground wire, maybe 16ga. from under the screw head that holds the regulator to a 3/8 bolt that I put in on the back of the head. I also put a little oil or grease on the threads of everything electrical so they won't rust. The regulator must have good ground. Also, clean the contacts inside the plug that plugs to the regulator. I usually use a small twisted up piece of scotchbrite and some break clean to rinse.

With the car running, I normally like to see 13.5 - 14.0v on a fully charged battery, no lights on.

 

[crytough]

Hi, I had a similar problem. The screws or bolts that hold the regulator to the firewall may be rusty, or the threads in the firewall rusty. I ended up adding a small ground wire, maybe 16ga. from under the screw head that holds the regulator to a 3/8 bolt that I put in on the back of the head. I also put a little oil or grease on the threads of everything electrical so they won't rust. The regulator must have good ground. Also, clean the contacts inside the plug that plugs to the regulator. I usually use a small twisted up piece of scotchbrite and some break clean to rinse.

With the car running, I normally like to see 13.5 - 14.0v on a fully charged battery, no lights on.

Thanks for the advice

 

[Mastertech]

To add to the comments already posted the charging voltage on a fully charged battery should be 14.2 volts. Any resistance in the circuit can cause the regulator to increase voltage to try and overcome the resistance. Check all the grounds first, alternator to block, regulator to firewall, negative battery cable to block, battery cable pigtail to rad saddle. Also check that the battery posts to clamps are clean and shiny. It's a good idea to polish all these connections and put a little grease or Vaseline on the bare metal and then tighten them down. I have seen black battery posts create so much resistance that as you increase engine rpm the voltage would just keep climbing well over 20 volts ! As a professional auto electric and tune up tech for 40 years I have always coated battery terminals and clamps with Vaseline inside and out. Corroded cables and battery terminals are then a thing of the past and never have to be worried about again.

 

[crytough]

To add to the comments already posted the charging voltage on a fully charged battery should be 14.2 volts. Any resistance in the circuit can cause the regulator to increase voltage to try and overcome the resistance. Check all the grounds first, alternator to block, regulator to firewall, negative battery cable to block, battery cable pigtail to rad saddle. Also check that the battery posts to clamps are clean and shiny. It's a good idea to polish all these connections and put a little grease or Vaseline on the bare metal and then tighten them down. I have seen black battery posts create so much resistance that as you increase engine rpm the voltage would just keep climbing well over 20 volts ! As a professional auto electric and tune up tech for 40 years I have always coated battery terminals and clamps with Vaseline inside and out. Corroded cables and battery terminals are then a thing of the past and never have to be worried about again.

 

[crytough]

I've had all kinds of electrical issues with this car. Good to know there is a master tech out there, thanks for the tip

 

[Cratos]

I have just put in a new regulator , alternator and optima battery, seeing 15 volts charge regulator has ground to block all the harness are new ( from year one)
went to advanced auto ( where I got the stuff) and he told me the optima's like 15 volts?? is this right? or will it flatten out after a while. I don't have anything extra running at this point still finishing up the car.

 

[Adam]

15 volts to the battery is fine... it could be more or less than that depending on the state of the battery. How much voltage do you have running to everything else?

 

[Chryco Psycho]

I bad diode in the Alternator can also cause overcharging , 14.2 - 14.6 is normal voltage

 

[Cratos]

brand new batt , alt and regulator .took it to advanced and had them test it he said 15 is ok with that battery. only power windows and lights and gauges hooked up.