1990 Ford Aerostar repair

Hello
Your system appears to have a red and yellow warning light. I have attached information on both. Depending on the light determines what needs to be accomplished. Codes need to be checked as discussed below and that will narrow down what it is telling you. I attached a code chart for you to review.

Brake System (Red) Warning Lamp
To check the brake system warning lamp, turn the ignition key to the Start position. The red warning lamp should glow momentarily. The warning lamp will also illuminate if the parking brake mechanism is not fully released. If the warning lamp fails to glow, service of the electrical system is indicated. If the warning lamp illuminates with the ignition key in the Run position, check and repair the conventional brake system as required. If the conventional brake system is found to be operating properly, check the anti-lock brake system for stored codes as outlined under ``Accessing Flashout Codes.'' In certain instances both the red and yellow warning lamps will glow simultaneously. If this occurs, check and repair the conventional brake system as required. If the red warning lamp continues to glow, refer to the ``Warning Lamp Condition Chart,'' Fig. 4, for proper diagnostic and testing procedures, then refer to Tests A through F, as required.

Anti-Lock Brake System (Yellow) Warning Lamp
To check the anti-lock brake system warning lamp, turn the ignition key to the On position. The yellow warning lamp should glow for approximately two seconds and should then shut off. If the warning lamp fails to glow, or glows continuously, refer to the ``Warning Lamp Condition Chart,'' Fig. 4, for proper diagnostic and testing procedures, then refer to Tests A through F, as required. In addition, if the warning lamp continues to glow during vehicle operation, check the anti-lock brake system for stored codes as outlined under ``Accessing Flashout Codes.''

Two warning lamps are located on the instrument panel to alert the driver to a system malfunction. The red brake warning lamp is used to indicate conventional brake system malfunctions such as low fluid level, parking brake applied and low vacuum conditions (diesel engines only). The yellow anti-lock system warning lamp is used to indicate proper warning lamp circuit operation (2 second illumination with ignition On or engine cranking). If yellow lamp comes on while vehicle is being driven, it is alerting the driver of an anti-lock system malfunction and yellow lamp can then be used to access flashout codes. This self-test feature contains codes to indicate area of system malfunction. When a malfunction is detected within the system, the computer module will shut down the anti-lock system and illuminate the yellow warning lamp on the instrument panel. This will permit normal braking and at the same time will store a code in the system memory which can be retrieved by grounding the diagnostic connector of the computer module and counting the number of flashes of the yellow light. If the ignition is turned off before diagnosis is performed, the code stored will be lost. In this case, the vehicle must be started and driven to reproduce the condition. If more than one fault exists, only the first code recorded will be displayed. Additional codes will output only after the first fault has been corrected.