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Charge System Warning Never/Always On

WARNING: This page is about a different car, the 1997 Mercury Cougar and 1997 Ford Thunderbird. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check charging system warning to determine if warning is always/never on. If warning is always on, go to next step. If warning is never on, go to step 8).
  2. Remove 3-pin voltage regulator harness connector. Turn ignition switch to RUN position. Measure voltage between ground and voltage regulator connector Light Green/Red wire. If voltage is more than zero, go to next step. If voltage is zero, repair open in Light Green/Red wire and retest system.
  3. Using jumper wire, connect voltage regulator connector Light Green/Red wire to ground. If indicator light is on, remove jumper and go to next step. If indicator light is off, replace light bulb or repair high resistance in light socket or Light Green/Red wire and retest system.
  4. Check for poor ground connections between voltage regulator and generator, generator and engine, or engine and battery. If all ground connections are clean and tight, go to next step. If required, clean and tighten all ground connections and retest system.
  5. Disconnect 1-pin "S" connector from generator. Measure voltage between ground and wiring harness "S" terminal White/Black wire. If voltage is zero, go to next step. If voltage is more than zero, repair White/Black wire which should be hot only when engine is running. Also check for swapped wires in regulator harness connector.
  6. Measure voltage between ground and "S" terminal on back of generator. If voltage is more than one volt and warning light is on with "S" connector disconnected, replace generator and retest system. If voltage is less than one volt, replace voltage regulator and retest system.
  7. Measure voltage between ground and voltage regulator connector terminal Yellow/White wire. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 11 (15-amp) in circuit No. 36 (White/Yellow wire) and replace as necessary. If fuse is okay, repair open in White/Yellow wire.
  8. Disconnect 3-pin voltage regulator harness connector. Turn ignition switch to RUN position. If indicator light is on, repair short to ground in Light Green/Red wire. If indicator light is off, go to next step.
  9. reconnect voltage regulator harness connector. Disconnect 1-pin "S" connector. Using jumper wire, connect harness "S" terminal (White/Black wire) to positive battery post. If indicator light is on, remove jumper and go to next step. If indicator light is off, remove jumper and go to step 11).
  10. Disconnect 3-pin voltage regulator harness connector. Measure resistance of wiring between "S" terminal connector at generator and "S" terminal (center) of regulator harness connector. If resistance is more than one ohm, repair open or high resistance in White/Black wire and retest system. If resistance is less than one ohm, check for a loose or bent pin in voltage regulator or connector. If pins are okay, replace voltage regulator and retest system.
  11. Start engine. Measure voltage between ground and "S" terminal on back of generator. If voltage is at least 1/2 of battery voltage, go to next step. If voltage is not at least 1/2 of battery voltage, refer to generator diagnosis in appropriate GENERATOR article in ELECTRICAL section.
  12. Measure voltage between ground and B+ terminal on back of generator with engine running at 2000 RPM and all accessories off. If voltage is more than 15.5 volts, refer to generator diagnosis in appropriate GENERATOR article in ELECTRICAL section. If voltage is less than 15.5 volts, replace voltage regulator.
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