Having worked on many older 70’s and 80’s cars and trucks at first, I thought it was no big deal just needed to swap out the external voltage regulator.
To my surprise, the voltage regulator now comes built into the onboard computer, which used is around $300-$600 dollars.
This was frustrating, to say the least, since the rest of the truck ran fine, and only the voltage was not regulated.
So remembering how the old Dodges worked with an external regulator, I began searching the forums looking to see how to wire one up and bypass the computer/PCM/ ECM.
To my surprise, there were many others with the same thought and experiences doing what I was looking for.
After reading through the forums and understanding how they are wired, I soon had my Dodge truck up and working in no time.
In this post, I will show how to build one or how I do it.
Items Needed to Build an External Voltage Regulator
Below are the parts I use. A junkyard also might have these parts on the cheap, or they can be ordered online and are low-cost parts.
All the parts should be less than $30-$35 dollars on eBay or Amazon.
- 1970s-1980s Dodge Voltage Regulator
- Voltage Regulator Pigtail
- Inline Fuse
- 14 Gauge wire (I color code mine red, black and green for good ground.)
- Screws to hold the regulator in place.
- Electrical tape.
- Wire Nuts (I solder the connections together, but some people use wire nuts.)
UPDATE: A seller on Amazon has a Dodge adjustable regulator and pigtail. The adjustable regulator would be a good option for those having problems with high voltage output.
The adjustment is a small potentiometer on the back of the unit that is turned with a small screwdriver to up or lower the output.
Dodge Voltage Regulator with Adjustable Potentiometer on Amazon
Standard Dodge Voltage Regulator on Amazon
Tru-Tech VR125T Voltage Regulator
It is a good idea to use an inline fuse.
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How to Build an External Voltage Regulator for Dodge, Jeep, Chrysler
Any Dodge external regulator from 1971-1989 is wired the same. I did find that the regulators from the 1970s put out less voltage than the 1980’s versions, but the wiring is the same.
The wiring is simple enough, with only three wires needed and a good ground.
The center pole on the regulator needs two wires, one that goes to the positive side of the battery and one that goes to the alternator.
The outer side pole on the regulator also goes to the alternator.
The labeled Red wire in the above picture goes to the positive side of the battery; the other two wires go to the back of the alternator.
If you look at the back of the alternator, there will be three connections, one large gauge wire going to the starter that hooks to the positive battery terminal and two small wires that go to the computer.
The two small wires are what regulate the voltage and are the only connections that need modifying on the alternator.
The two wires that go into the alternator from the voltage regulator do not matter and are interchangeable since it is alternating current.
The only wire that is very important (since it will fry the regulator if done wrong) is the center pole on the regulator that goes to the positive battery terminal.
If the center terminal wire going to the positive side of the battery is wired wrong, the regulator will fry.
The center regulator wire will also drain the battery slowly if left connected with a vehicle while not running.
To stop the battery from draining, it is usually wired into the fuse box on at least a 20 Amp fuse, so it breaks the connection when the vehicle is turned off.
Another option is to put in a manual on/off switch somewhere that will break the connection manually.
Either way, simply remember if it is left hooked to the positive terminal, it will slowly drain the battery.
Another important step is that the external regulator must have a good ground to the alternator. If there is no good ground, then the voltage will swing wildly.
A simple way to be sure it is grounded well is to run a ground wire from the alternator casing to the external voltage regulator casing.