HID Ballast

This procedure covers the replacement of a failed HID (High-Intensity Discharge) headlight ballast on a 1994-2007 Dodge Ram 2500 with the 5.9L Cummins diesel engine.

Warnings

Tools required

Parts

• HID ballast (35W or 55W, verify original) × 1 — Use OEM specification or aftermarket equivalent matching original wattage
• Zip ties or mounting hardware (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn off all lights and accessories
3. Allow engine to cool completely if recently operated
4. Open hood and secure with prop rod
5. Identify which ballast has failed (driver or passenger side) by checking which headlight is not functioning or flickering

Procedure

1. 1

   Disconnect battery negative terminal
   Using a 10mm socket, loosen the negative battery terminal bolt. Remove the negative cable from the battery post and secure it away from the battery to prevent accidental reconnection. Note this Cummins truck is equipped with dual batteries; disconnect the negative terminal on both batteries to ensure the system is fully isolated. Wait at least 5 minutes for HID ballast capacitors to fully discharge before proceeding.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
2. 2

   Access headlight assembly area
   On the affected side, locate the headlight assembly. You may need to remove the grille or headlight bezel depending on model year. Because any HID system on this truck is aftermarket, ballast location varies by installation. Trace the wiring from the HID bulb to locate the ballast; it may be mounted behind the headlight, on the inner fender, or elsewhere in the engine bay depending on how it was installed.
3. 3

   Locate the HID ballast
   The HID ballast is typically mounted on or near the headlight assembly, often secured to a bracket behind the headlight housing. It will be a rectangular metal or plastic box (approximately 4x6 inches) with electrical connectors on one end. Trace the wiring from the HID bulb to identify the ballast location.
4. 4

   Disconnect ballast electrical connectors
   Identify the input power connector (from vehicle harness) and output connector (to HID bulb). Press the release tabs and carefully disconnect both connectors from the ballast. Note the orientation and routing of wires for reinstallation. If connectors are corroded or difficult to remove, use a flathead screwdriver to gently pry the release tabs while pulling the connector.
   ⚠Do not pull on wires to disconnect connectors. Always grasp the connector body and use release tabs to avoid damaging wiring.
5. 5

   Remove ballast mounting hardware
   The ballast is typically secured with either bracket bolts or module mounting bolts. Remove the fasteners securing the ballast to its mounting bracket or the vehicle body. On some models, the ballast may also have a ground wire secured with a separate bolt. If present, remove the ground bolt and note its location for reinstallation.
   ℹ️If a ground wire is present, clean both the wire terminal and mounting surface with a wire brush or sandpaper before reinstallation to ensure proper grounding.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
6. 6

   Remove failed ballast
   Once all mounting hardware is removed, carefully extract the ballast from its mounting location. You may need to manipulate the ballast around other components or slide it out of a retaining bracket. Note the orientation and position of the ballast for proper installation of the replacement unit.
7. 7

   Inspect mounting area and connectors
   Examine the mounting bracket for damage or corrosion. Check all electrical connectors for corrosion, burnt pins, or damage. Inspect the wiring harness for chafing or damage. If the ground connection point is present, clean the contact surface thoroughly with a wire brush until bare metal is visible.
8. 8

   Install new ballast
   Position the new ballast in the mounting location, ensuring it is oriented correctly to match the original installation. If the ballast uses a mounting bracket, slide the ballast into the bracket first. Align all mounting holes with the corresponding attachment points on the vehicle.
9. 9

   Secure ballast mounting hardware
   Install and hand-tighten all mounting bolts. If a ground wire is present, ensure the contact surface is clean and install the ground bolt first. Snug all mounting fasteners securely by hand/ratchet without overtightening, as aftermarket ballast brackets are light-duty; no OEM torque specification exists for these fasteners. Ensure the ballast is firmly secured and does not move when pressure is applied. Ensure the ballast is firmly secured and does not move when pressure is applied.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
10. 10

    Reconnect electrical connectors
    Apply a small amount of dielectric grease to the inside of each connector to prevent corrosion. Connect the input power connector from the vehicle harness to the ballast input, then connect the output connector to the HID bulb. Ensure both connectors click fully into place and the locking tabs are engaged. Gently tug on each connector to verify secure connection.
11. 11

    Secure wiring and verify routing
    Ensure all wiring is routed away from hot engine components, sharp edges, and moving parts. Use zip ties to secure wiring to existing harness routing points if the original ties were damaged during removal. Verify that no wires are pinched or under tension.
12. 12

    Reconnect battery negative terminal
    Clean the battery terminal post and cable end with a wire brush if corrosion is present. Reconnect the negative battery cable to the negative battery post. Using a 10mm socket, tighten the negative battery terminal clamp bolt securely (approximately 5-8 Nm / 4-6 lb-ft) without overtightening. Note this Cummins truck has dual batteries; verify the correct negative terminal. Do not overtighten as this can damage the battery terminal.
    ⚠Overtightening battery terminal bolts can crack the battery case or strip the terminal threads. Use a torque wrench and do not exceed specification.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Reinstall any grille components or trim pieces that were removed for access
2. Verify all tools and parts have been removed from the engine bay
3. Close the hood securely

Verification

• Turn the ignition to the ON position without starting the engine. Turn on the headlights and verify both low and high beams function properly on the repaired side
• Start the engine and allow it to run. Verify the HID bulb ignites within 5-10 seconds and reaches full brightness within 30 seconds
• Check for any flickering, abnormal color, or intermittent operation that would indicate a faulty installation or additional issues
• Verify no warning lights are illuminated on the instrument cluster
• Test headlight operation with engine off, at idle, and at elevated RPM to ensure proper function under all electrical load conditions
• If available, use a multimeter to verify the ballast is receiving proper input voltage (approximately 12-14V with engine running)

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