Battery - Alternator Charge Wiring with Ammeter

Chrysler, Dodge, Plymouth and similar charging systems wired through the instrument cluster.

Summary
Contents
It is critical to understand how the charging circuit is wired into the rest of the electrical system.  Even if you don't work on the car, you can prevent a fire by understanding that the charging circuit can not handle high loads for any length of time.  If the ammeter swings far to one side or the other and does not quickly return close to center, the circuit will fail.  The fusible link should fail first, but any loose or oxidized connections may melt and even ignite nearby flammibles before that happens.  The ammeter shows the amount of current flow to or from the battery.
How and why this circuit can not support sustained high loads, and what can be done solve various problems is covered below.  
Charge Wire Diagram; Alternator to Battery
Charge System Operations
 - Run when battery is charged
 - Run when battery is slightly discharged
 - Start
Problems
Solutions
Complete Charging System Wiring Diagrams

page 2: How Fusible Links Work in Charging Systems with Ammeter

Credits: This page is an edited and shortened version of explanations and illustrations presented on several forums by mopar enthusiast who goes by screen name "Nacho-RT74"

The Main Charge Circuit Wires; Alternator to Battery.

The battery is recharged by the alternator through a wire that also connects to the wiring main junction.
Notice the main junction is located between the alternator and the ammeter.
  Internally the ammeter has a shunt that carries most of the current.


Charge System Operations:

  Red arrows represent current.  Heavier arrows represent more current. 

RUN When Battery is Fully Charged

When the battery is fully charged, no power flows through the charging wires or ammeter.


RUN when Battery is Somewhat Discharged (after Start)

Current from alternator goes to main junction.
Only current for recharging the battery goes through the ammeter.



START

The battery may supply over a 100 amps for several seconds directly to the starter when the relay closes.
A relatively small amount of current trips the relay and powers the ignition.


Problems

Solutions

Connections:
1. Check for oxidation, corrosion, loose connections especially at bulkhead.  Clean, tighten, fix as needed.
2.  An option is to create better connection or direct wire the  feeds through the firewall, either in addition to, or replacing the bulkhead connector.
 This is essentially the same as Chrysler's modification for certain fleet use applications and keeps the ammeter.
3. Another option is to rewire the circuit using a remote shunt and ammeter, or voltmeter instead of the integrated ammeter.  At least some Chrysler products used a remote shunt ammeter starting around 1975 as did some other companies (but not AMC/Jeep).  (ref. Rick E. Mopar Action reprinted at allpar.com)

High Rate of Charging
:   Maintain battery in good condition.  If battery is low, keep alternator speeds down and monitor ammeter.  Shut off if current is excessive. Use an alternator that can keep up with expected power needs at idle.  Do not simply use an alternator that is rated high output, especially if not needed.  Output goes up with rpm, if the extra current is not needed but the battery is low, it will send all that current into the charging circuit.    (More info on alternator rating games, on Speedtalk forum)

Circuits: If adding headlight relays or other high current circuits, draw power directly from the alternator.  Add fuse or circuit breaker for each new circuit.

Complete thread by NachoRT74 et al on improving the charging system while keeping the ammeter.  (on Dodge Charger forum)


Complete Charge System Wiring Diagram

1985 AMC Jeep SJ, Charge and Headlight Diagrams (has its own page)

1967 Plymouth Barracuda:

Alternator system using positive field regulator (single field wire).
Wire colors will vary with year, make, model.

This Website:
'67 Barracuda Main Page
'85 Grand Wagoneer Main Page

Disclaimer:
    Advice and information provided for discussion and to be helpful.  Neither myself or Nacho can be liable for your decisions or workmanship. You need to make your own decisions, and know about or discover the risks before barging ahead on any endevour.


Claimer:
    The information and pictures on this page are free to use and share by all and may not be sold.  You may not sell anything that I or Nacho has written or illustrated.  If you wish to quote something, you are free to do so.  All I ask for is proper credit.  Credit items on this page other than 67 Complete Charging Diagram  to NachoRT74. 

May 2017