Front Heated Windshield System

The Heated Windshield System provides quick clearing of ice from the windshield even under severe winter conditions. The windshield contains a transparent internal resistive coating that heats when power is applied to it. Power for the system comes directly from the Generator. The engine must be running to operate the system.

Components

The system consists of the special windshield, a Heated Windshield Power Module, a Heated Windshield Control Module, a special Generator and a Heated Windshield Switch. The PCM controls engine idle speed.
The Heated Windshield Control Module receives various inputs and uses electronic logic to determine when the system should turn on.
The Generator is a special model. Three phase AC voltage from the stator is brought out to a connector on the back of the unit. The Generator can continue to supply its normal DC voltage while AC power is being supplied.
The Heated Windshield Power Module receives AC power from the Generator, increases the voltage in an autotransformer, rectifies it to DC and supplies it to the windshield. Voltage at the windshield is between 50 and 85 volts DC. The Heated Windshield Control Module also contains a relay that switches its output on and off.
The PCM increases idle speed in Park or Neutral during Heated Windshield operation.

Operation

With the vehicle's engine running, the Heated Windshield System may be turned on by pressing the Heated Windshield Control Switch. The Switch momentarily grounds terminal A3 of the Heated Windshield Control Module. The Control Module begins the turn-on sequence after turning on the Control Switch System On LED.
The Control Module checks that more than 11.2 volts is present at terminal B6 to ensure that adequate battery voltage is available for the other circuits. While the windshield does not draw current from the Battery, it does reduce the charging current available to the Battery.
The Control Module also checks that the Windshield is not cracked. This is sensed at Control Module terminals A2 and B4. (See Special Feature.)
If all the above conditions are met and the Transaxle is in PARK or NEUTRAL, the Control Module signals the PCM to increase engine idle speed by grounding Control Module terminal A4. The PCM will respond by increasing engine idle speed.
The Control Module then switches on its output at terminal B1 to energize the Heated Windshield Power Module Relays. Power is then drawn from the Generator, stepped up and rectified by the Power Module and supplied to the Windshield, which heats.
The Control Module incorporates a timing feature similar to the Rear Defogger. The first time the Control Switch is pressed after starting the engine, a 4 minute on cycle begins. Pressing the Control Switch again will result in a 2 minute cycle. If the Ignition Switch is turned OFF for more than 5 seconds, the timing cycle will reset to 4 minutes. The system may be turned off by depressing the Control Switch again.
If the Transaxle is shifted out of Park or Neutral while the Heated Windshield is in the first cycle, the first cycle will last only 2 minutes. If 2 minutes have already elapsed, the cycle will finish its 4 minute duration.

Special Feature

CRACK DETECTION. The crack detection circuit monitors the voltage at two points in the system. They are at the vertical bus (reference voltage) and at the narrower vertical sense trace (sense voltage). A crack through either or both of these will cause a voltage difference between terminals A2 and B4 of the Control Module. If the Control Module senses a difference of more than 10 volts between these terminals, it will shut the system down.