Chrysler Full-Size Trucks 1989-1996 Repair Guide

Disconnecting the Cables



Make sure the battery cables are connected to the correct battery terminals. Reverse polarity may damage electrical components, particularly the (expensive) engine controller.

Before performing work on the vehicle, it is usually required to disconnect the battery from the electrical system. Whether this is to prevent a mistaken start-up or electrical power from being supplied to the system components, the certain measure is to shut off the power at the source.

To disconnect the battery cable(s), perform the following:

  1. Make sure the ignition switch is OFF .

Disconnecting the negative battery cable FIRST with the ignition turned OFFis required to prevent unwanted surges through the electrical system. If a voltage spike is fed through the system, delicate and expensive componentry (like the engine controller) could be destroyed in fractions of a second.

  1. Use the appropriate size wrench(es) to loosen the hardware on the cable clamps. ALWAYS begin with the negative battery cable.

Diesel engine models have two 12 volt batteries connected in parallel (positive-positive/negative-negative). The secondary on the passenger's side is dedicated to providing current to the intake manifold air heater. The primary battery on the driver's side is dedicated to all other vehicle electrical requirements. In order to ensure accurate diagnostic results, these batteries must be disconnected from each other and from the vehicle electrical system when being tested.

  1. If necessary, use a puller tool designed for battery cable clamps and remove the clamp, then isolate it from the battery terminal.
  3. Remove the positive battery cable, if required, once the negative battery cable has been removed.