nifty toyota trick

My dad's '94 Toyota Camry has a pretty nifty headlight trick that I want to duplicate in my '88 Bronco II. When you shut the car off, the headlights stay on until you open one of the front doors. Once the door is opened, the headlights shut off. If, while door is open and lights are off, you flick the headlight switch off and then back on, the headlights turn on again, regardless of door position or ignition key position.
I tried to figure it out on paper, but I couldn't quite wrap my mind around it. I imagine it would use a few relays and tie into the door switches.
Any help would be awesome.

brownbeard wrote:

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If, while door is open and lights are off, you flick the headlight switch off and then back on...

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Do you mean "you flick the headlight switch ON and then back OFF"?

Also, in the method as last described (where the headlights turn on again regardless of door position or ignition key position), how do you switch them off?.


The first part "staying on" can be done with the headlight relay latching itself on (eg, output 87 feeds coil 86 through a diode, and other 86 triggers (from switches etc) are also fed via diodes), and then something to break that "feedback" circuit.
But it sounds like it's a battery protection feature... IE, headlight switch is on, ignition is turned off. Instead of ignition controlled headlamps (common on older Italian etc autos) or a buzzer when the door is opened (Japanese etc), it cuts the headlights when the door is opened - thus suiting forgetful hearing-impaired drivers that enjoy after dark observations.
But more operational behavior is required for me to provide further suggestions.

Radio On Until Door Opened (Retained Accessory Power) (link)

If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position.   If you want to prevent 12V+ from feeding back into the accessory circuit or have more than one device on this circuit and do not want all of them to stay powered, you can isolate the device you want to stay powered by cutting the accessory wire going to it and adding two 1 amp diodes and an additional relay as shown below. The first diode near the top left of the diagram is to prevent 12V+ from going back into the accessory circuit. The second diode between terminals 87 and 86 prevents the radio from pulling current through the first diode. If the second diode is not in place, the first diode will become toast. The additional relay is needed to prevent the radio from turning off when the key is in the accessory position and a door is open.   Below is the same set up as above for positive door triggers.

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

A rephrase:
The headlights behave normally all the time. But, when you turn off the motor and open the door, the headlights shut off, even though the switch is still in the ON position. If you want to have the lights on, either start the car or turn the switch OFF and then back to ON.
Basically, it ensures that I won't leave my headlights on when I park the car.

Thanks for the diagrams. I think its just what I needed to make this work.