Charging issues

A regulator issue can cause it. I've seen some reg's not ground the I (switch) circuit, yet the alt worked just fine.

Disconnect the green wire at the alternator and ground it. Then turn the ignition switch to run and
watch the warning light. If the light lights, the circuit is good. If not the bulb is out or the wiring is bad.

Here's why this works: there is a 500 ohm resistor in line with the wiring and is wired in parallel with
the warning light. Grounding the circuit provides a path for the current so the light will turn on. The
light bulb and the 500 ohm resistor limit the current that flows through the wire. That keeps from
making a short circuit that would create smoke and sparks.

Diagram courtesy of Tmoss & Stang&2birds


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website
host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/
Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif