1984-86 Pontiac Fiero Headlight Repair

1984-1986 Pontiac Fiero used a Torque Switch in the Headlight Actuator and external Relays to switch off and on the Actuator power circuit.

Here's how it works:

The headlight door motors reverse direction by reversing polarity

When a motor reaches its limit, one of the 'wires' is disconnected from the motor by the HTS.

Each motor has three wires. The combination of the blue wire, gray wire, and green wire provide polarity reversal to the motor (to make it able to run in both directions) and to run each motor from its resting state, after it has shut off.

The Driver and passenger sides Motors are identical electrically.

This is the wiring use arrangement:

RIGHT HAND MOTOR
              Blue     Green     Gray
UP:                      (+)         (-)
DOWN:    (+)         (-)

In order to run the motor up, the system connects the green wire to the hot side and the gray wire to ground. To run the motor down, the system connects the blue wire to the hot side, and the green wire to ground.

The Driver side motor operates the same, except for its blue wire is actually blue with white stripes.

There is an actuator relay for each light mounted on the body of the light housing. There is also an isolator relay, mounted on the fender wall on the driver's side. When operating properly, the two actuator relays act identically.

The actuator relays get their instructions from the isolation relay. When the motors need to run down, the isolation relay is not energized, the blue (and blue/white) wires make with the hot side through the closed contacts of the isolation relay (which is not energized), and the ground is furnished to the motor through the closed contacts of the actuator relay until the circuit is broken by the HTS. When operating properly, neither the motors nor the relays draw any current in the full down position.

When it's time to go up, the actuator relays are energized when the pink wires coming from the isolation relay are connected to the hot side through the newly closed contacts of the isolation relay, the isolation relay is energized because the yellow wire coming from the head light switch is now hot. When the actuator relays are energized, they furnish 12v from the always hot red wires, through their newly closed contacts, to the green wire. The motor is grounded through the newly closed contacts of the actuator relays. The motors will run up until the circuit is broken by the HTS. When operating properly, with the light doors in the full up position, all relays are energized and draw current, but the motors do not.

There are nonsensical things about this circuitry: When the motors are running UP, both the hot side and the ground are furnished by and through the actuator relay. However, when the motors are running DOWN, only the ground is furnished by the actuator relay because the blue and blue/white wires do not run to or through the actuator relay.

Similarly, when the motors are running down, the hot side is supplied through the isolation relay, when they are running up, the hot side is supplied not by through the always hot fusible link.

It is easy to swap the actuator relays from side to side. If the symptoms change with them, than its probably the relays. The actuator relays look similar to the isolation relay, they are very different, they cannot be swapped.

Trouble shooting Tips:

Headlight Actuators that "run on" are usually caused by a failure in the Actuator of the Gear, or less often by the Torque Switch. When the Actuator Gear fails, the Actuator Motor can never create enough torque to activate the Torque Switch.

Problems with the Isolation Relay or Actuator Relays can also occur.

Repair Tip: Here are a few practice tips for diagnosing the problem.

1. If the Actuator Motor stop turning when the Headlight Door reaches full closed or open positions, but the motor is still trying to run, the most like cause is the Actuator Relay.
2. If the a Actuator Motor continues to run when the Headlight Door reaches full closed or open positions, the most likely cause is a failed gear inside the Actuator.
3. If the the Actuator Motor, or Motors don't run when the Headlight Switch is activated, try wiggling the Headlight Switch from side to side while switching it off and on. The Headlight Switch can become worn and also cause problems. Note when the Headlight Switch is at fault, usually the problems are intermittent.