1993 BMW 740iFACTORY OEM SERVICE PROCEDURE

Unloader Relay

  1. Check charging system fuse No. 28. Replace fuse if necessary. Remove unloader relay. Turn ignition on. Check for battery voltage at relay socket terminals No. 4 and 5 (Green/White wires). If battery voltage is present, go to next step. If battery voltage is not present, repair circuits.
  2. Ensure relay socket terminal No. 2 (Brown/Black wire) is grounded. If socket terminal is grounded, go to next step. If socket terminal is not grounded, repair ground circuit.
  3. Start engine and ensure charge indicator light goes out. If charge indicator light remains on, check charging system. If charge indicator light goes out, go to next step.
  4. With engine running, ensure a minimum of 12 volts is applied to relay socket terminal No. 8. If voltage is as specified, go to next step to check voltage to accessories. If voltage is not as specified, repair wire to alternator.
  5. Turn ignition switch off. Connect a fused jumper wire between relay socket terminals No. 5 and 6. Turn ignition switch on. Ensure battery voltage is supplied to relay operated systems (i.e., rear defogger relay, heated seats, automatic A/C, etc.). If voltage is not present to these systems, repair circuits. If voltage is present to these systems, go to next step.
  6. Install unloader relay. Start engine and ensure battery voltage is present at relay operated systems. If relay does not work, replace unloader relay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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