89 dodge with cummins overcharging battery

[markct]

i have a 89 dodge D250 truck with the 5.9 cummins. it has been overcharging the battery, i put a new voltage regulator on it, its the external type mounted on the firewall, and it was then charging well over 15 volts, i put the old one back in and it was back to a bit under 14.5 volts which is still high, any ideas on what else to check, could the alternator itself be bad, i thought the regulator was all that would realy affect the voltage like that but i dont know

 

[workinallthetime]

duno about dodge but a gm in perfect condition charges at 14.4 all day long, i had a gm that would charge from 14.4 to almost 16 volts, ate up a battery every couple of years but thats it.

 

[Dmace]

With the vehicle running and idling, the voltage read across the battery should be at least 14 volts. If it was only 12 volts it wouldn't charge the battery, it would barely sustain charge. Anything above idle, the voltage can go up to as much as 16 volts. My 94 F350 diesel has a 190amp alternator I just replaced. It was only pushing 11.5 volts and now generates 14.8 at idle and 15.5 anything above idle.

The voltage regulator will not change the amount of voltage sent, instead it regulates the amount so that there is always a constant flow. So if your lights are blinking or going bright-dim-bright-dim while idling, then the voltage regulator is gone. Usually the dash lights are the first thing you notice flickering.

 

[RichNJKubota]

14.4 to 14.6 volts is normal.

 

[scott_vt]

Afternoon Mark,
I agree with Workinallthetime and Rich, thats a normal reading, I have a 2000 Dodge Ram although its a 5.9 liter and those are the readings Im getting !

 

[Mickey_Fx]

i have a 89 dodge D250 truck with the 5.9 cummins. it has been overcharging the battery, i put a new voltage regulator on it, its the external type mounted on the firewall, and it was then charging well over 15 volts, i put the old one back in and it was back to a bit under 14.5 volts which is still high, any ideas on what else to check, could the alternator itself be bad, i thought the regulator was all that would realy affect the voltage like that but i dont know

Personally I wouldn't like to see voltage above 14.25 unless the vehicles use is for short durations. A nom 12V LA battery the voltage can rise to 13.9 without over charging issues. 14.25 is about as high as you want to go without compromising your battery life. The tech books I've read say charge voltage should range between 2.2 and 2.4V per cell.

I think you've mentioned something in your post that gives a clue. I sound like after you reinstalled the original VR the voltage was lower that it was initially but still higher than you would like. This sound to me like there is a faulty connection to the VR and it's reading the voltage lower than the battery actually is. I'd recommend you trace the wiring all the way back to the battery and check every connection looking for faulty connections. Start at the VR and take a voltage reading. How much lower it it then the battery. You want to get the voltage at the VR to be as close to the battery as you can.

YMMV

 

[markct]

well i found the trouble, at one time someone replaced the plug that plugs into the voltage reg, they had spliced it with crimp connectors and one was badly corroded, replaced the connectors with heat shrink type crimp connectors and it charges right about 14.2 so thats about where it should be i guess, thanks for the advice everyone, i always sorta thought 14 was about the max voltage, i didnt realize some stuff charges a bit higher than that

 

[Renze]

My Volvo also charges to 14.2 Volt... Previously to 14.5 volt, but the overhaul shop didnt have the exact Bosch charge controller in stock.

When my brothers old Mercedes 200 D was overcharging a couple of years ago, it toasted the battery.