automatic headlight control?

**coolbet13** · 12-15-2005, 05:38 AM

Our cars have the automatic lights that turn on when it gets dark but is there any way to ajust how much light it takes to make them come on (ie Darker outside) when they come on?

**DrMilhouse** · 12-15-2005, 02:15 PM

You can't really change that, but you can defeat them completely so they do not control it at all. You just have to lift up the front of the dash cover to expose the photocell and jump the two wires together so the car thinks it's ALWAYS day time.

You might be able to find a more sensitive photocell, maybe from radioshack.com or some other electronic component place.

**FantaZGuy28** · 12-16-2005, 03:25 AM

Or if your lazy just put your ebrake up 1 click and that will take care of the problem.

**fordkiller** · 12-19-2005, 11:41 PM

I did this today but completely unplugged the whole thing, it worked because my lights dont come on any more at night unless i turn them on, but my blinker doesnt work anymore. Is there any way to do this without unplugging it?

**345hpss** · 12-21-2005, 07:28 AM

The way it works: There is a photoresistor in the dash. This component acts like any other sensor, but with light. As light hits the sensor, the resistance of the sensor goes down, and as darkness falls and less light is on the sensor, the value goes up.

The light control module is preprogrammed to activate the lights when it sees a certain resistance on the circuit. Theoretically, you could modify the sensitivity by adding additional resistors in parrallel with the photoresistor, thereby creating an overall lower resistance load on the circuit.

The easier thing to do is just disable the auto headlamps. Here is my own page and photographs of how to perform this very simple mod.

fasidemedia.com/personal/mike/cars/camaross/mods/autoheadlamps/disableautolamps.htm

Doing this mod this way does not disturb anything with the car (ie blinkers, headlamps, abs, etc, as you are merely replacing the "sensor" with a fixed value resistor). Just as an aside, the system does fail safe... if your resistor should fall out or otherwise fail, the lights will come on and stay on. You can observe this by merely disconnecting the photoresistor and leaving the circuit open.

**coolbet13** · 12-26-2005, 05:20 PM

can I not just put some kind of knob in to adjust the resistance instead of the 1K res? cause I still want them to work just in darker light

**345hpss** · 12-26-2005, 06:02 PM

Originally Posted by coolbet13

can I not just put some kind of knob in to adjust the resistance instead of the 1K res? cause I still want them to work just in darker light

Well how much do you know about basic electronics?

The easiest way to do it, and a way I had thought about doing it, would be to insert a DPDT switch into the circuit. Send one side of the switch through the existing photoresistor circuit, and the other side of the switch through a new circuit you create that contains just a 1k resistor. Now, that switch would control whether the auto headlamps would activate or not. So in the first position, you would have the factory behavior, and in the other position, they would never work automatically.

If you want to "fine tune" it perse, you could theoretically add a variable resistor in parallel with the existing photoresistor. Since more light makes the resistance of the circuit lower, you would be able to adjust the overall circuit resistance to be equal to the photoresistor or lower than the value of the photoresistor. You would have to do some math to calculate exactly what you would need, and quite honestly I think it would be more trouble than it would be worth.

**coolbet13** · 12-26-2005, 07:31 PM

yes I know enough to do some damage! but yeah I follow you but we need to figure this out I still want my DTR's (park lights) to work but just a lower the amouth of light it takes to activate the auto headlights

**345hpss** · 12-26-2005, 07:43 PM

Originally Posted by coolbet13

yes I know enough to do some damage! but yeah I follow you but we need to figure this out I still want my DTR's (park lights) to work but just a lower the amouth of light it takes to activate the auto headlights

As long as you do your modifications to the photoresistor circuit ONLY, you are not going to alter anything in regards to DRLs, turn signals, hazard flashers, etc.

If you mess with the light control module itself, you risk disrupting those functions.

**coolbet13** · 12-28-2005, 06:07 PM

Originally Posted by 345hpss

As long as you do your modifications to the photoresistor circuit ONLY, you are not going to alter anything in regards to DRLs, turn signals, hazard flashers, etc.

If you mess with the light control module itself, you risk disrupting those functions.

Right, so would you be willing to help me come up with some sort of way of doing this?

**Geldingmakr** · 01-03-2006, 10:04 AM

My e-brake does not over ride the atuo on... how do i trouble shoot this?

**coolbet13** · 01-03-2006, 05:09 PM

When the car is running and the E-brake is up does the brake light come on in the dash? If not.... try the switch that tells the car the brake is up. I'm not sure if it's a normally open switch or closed but you should be able to take it off and Resistance check it with a meter.

**Geldingmakr** · 01-03-2006, 05:12 PM

thanks i'll check it

ssilicon · 01-19-2006, 05:36 PM

Here is THE answer to this. I have done it myself and it works as advertised. I just created a "solder bridge" between the two points since they were so close together. This is my 1st post. It won't let me post a URL yet, presumably to weed out those who just want to spam. Anyway, this is not a spam, it is totally good info on this topic. I will try to space out the URL so that it will take.

www xse com /leres/ss/drl.html

**BradZ01** · 01-20-2006, 12:59 AM

I use the E Brake trick. FYI, it will not turn them off if they come on for example when your car is in the garage when you start it, or if you are out cruising and they come on it will not shut them off. You must pull the E brake up BEFORE you turn the key on. Just 1 little click up which is just enough to turn the "Brake" light on the dash on.

**02z28ls1** · 01-22-2006, 08:52 AM

You could put a switch before the e-brake switch in the console-with the flip of the switch before starting the car you could disable the automatic headlight circuit. If I remember right it grounds out-so a switch that would interrupt the circuit ahead of the factory switch and would go to ground would do the trick. Or how about an even easier way of modifying the photocell-experiment with different light filters over the cell itself-by varying the darkness of the light filtering you can decrease the amount of light the cell sees and make it come on earlier-but not later.With a combination of the two previously described methods you should have all the control you need.