Often during wet inclement weather, the ambient light level is too high for the autolamp system to automatically engage the headlamps, but it is desireable for the lights to be illumunated to increase visibility to other motorists. On 2001 and later crown victorias, the headlamps and parking lamps automatically illuminate when the windshield wipers are turned on. But on earlier vehicles, the autolamp system is not interfaced with the windshield wiper circuit.

As explained on the autolamp retrofit page, when +12V is present on autolamp enable input of the lcm, the headlamps will turn on around 20 seconds later. And after the input is removed, the headlamps will shut off around 20 seconds later.

The first part of the project is finding a switched voltage source that only provides +12V when the windshield wipers are engaged. The wiper switch on the steering column uses a resistor multiplex bus so it will not be a suitable voltage source without designing extra circuitry.

But the windshield wiper motor has two limit switches built into it to control the intermittent delay feature and allow the wipers to properly park themselves. When the wipers are parked, both of the limit switches rest at ground. When moving, one will be at +12V until the end of the travel range at which point it will pulse to ground and the other one will momentarily pulse to +12V.

If the limit switches were connected directly to the ambient sensor, the ambient light sensor output would be shorted to ground when the wipers were parked. This would damage either the demand lighting output of the LCM or the sensor if the fuse did not blow first. This would also create crosstalk between the two limit switches so that the wipers would not park properly.


But using a pair of diodes to interface the limit switches to the lcm will alleviate the problems mentioned above and provide a +12V source whenever either limit switch has +12V present on it. With the revision of the lcm software in my 98' police interceptor, connecting only the black/pink wiper park switch to the lcm autolamp enable input was sufficent to trigger the lamps when the wipers were on. But to be on the safe side, I diode connected the other limit switch to the LCM anyways to remove the periodic 0V pulses.

The wiper control module is a black box held on with a single bolt above the ashtray and below the climate controls. Accessing the module is easiest if you remove the ashtray first. The wires that we're after are ([Pin 6] - Black/Pink)  and ([Pin 13] - Red).

At the LCM located above the gas pedal, we're after the bottom connector Pin 7 with the White/Pink wire.

In 01' ford added wiper activated headlamps to the crown vic, by connecting one of the limit switches to a new input pin to the c2027 lcm connector. When Pin15 on c2027 recieves a +12V input for several seconds, it turns on the headlamps and then waits several seconds before turning them off after the signal is removed. So if the vehicle operator momentarily uses the winshield wipers for a quick washer spray and wipe, the lights will not engage. One common complaint about the wiper activated headlights on 01' & 02' vehicle's is that there is no way to turn off the headlights without also turning off the wipers. If black/pink input wire to the lcm from the wiper control module were cut, this would disable the wiper activate headlights all together. If the modification mentioned above for 95'-00' vehicles were now done to the 01' or 02' vehicle, the wiper activate headlight feature would only be active when the headlamp knob was in the autolamp position.


In conclusion, the wiper activated headlamp retrofit project works well in my vehicle. And it also helps me avoid leaving the headlamps on when I shut off the vehicle. I have grown so accustomed to the delayed exit feature leaving the lights on, that I often don't remember to shut off the lights after I manually turn the on by the headlamp switch until after the [engine off/lights on/door ajar] warning chime sounds.

Questions or Comments?

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