What Is DRL Halogen Voltage? (<12V for Automotive relay trigger ?)

Hello.

I asked this in a different thread, but thought it might be best as its own thread:

A - Does anyone know what the voltage of the halogen high beam/DRL's drop down to?
B - Whats the minimum trigger voltage for standard automotive relay?

I ask, as i want to make sure that a standard 12 volt car relay will be triggered by the DRL's less than 12 volts when the high beam/drl's are automatically turned on.

thanks!
 
From looking at Bosch relay specs, I think the "pull-in" voltage is around 8 volts, and the drop-out voltage is between 1 and 5 volts. http://www.bcae1.com/relays.htm way on down the page lists pull-in/drop-out specs.

If no one else posts the DRL voltage here, I'll check it myself on our car and post the results.
 
No need to waste time with it... most relays will work fine at that reduced voltage... DOT rules has set limits on how dim DRLs can be, and because there's only so many different kinds of headlight bulbs out there, the reduced voltages are pretty similar across the board on many cars
 
...Bosch relay specs, ... "pull-in" voltage is around 8 volts, and the drop-out voltage is between 1 and 5 volts. http://www.bcae1.com/relays.htm.

THIS IS GREAT!!! Thanks Patrick!

No need to waste time with it... most relays will work fine at that reduced voltage... DOT rules has set limits on how dim DRLs can be, and because there's only so many different kinds of headlight bulbs out there, the reduced voltages are pretty similar across the board on many cars

Which is pretty much what the spec sheet Patrick posted above inplies... This opens up lots of possibilities for me/us!! All you need is to tap into the high beam wire with a relay, and run whatever aftermarket LED. The relay will turn on with the "pull in" 8 volts (-/+) from the DRL's, and supply full 12 volts to aftermarket lights.



If no one else posts the DRL voltage here, I'll check it myself on our car and post the results.

I still think it would be good to know what exactly "this" car runs at before i go pulling off the front end and cutting in some LED fogs. I would appreciate you posting what you test.
 
DRLs AFAIK, is suppose to run at 13.5 volts above. Hence when you turn off the engine and the voltage drops to below 13v, it would automatically turn off.

Sent from my ASUS_Z012D using Tapatalk
 
Has there been any movement on this? I'd still love to know EXACTLY what voltage is there.

@Luv2Lafmcc DRL UPDATE!!! I just put my multimeter across the high beam bulb plug to check the voltage. What I found was that the high beam bulbs receive FULL BATTERY VOLTAGE 13+ V (engine running) for both DRL use and high beam use. One oddity, though, is that when one high beam harness is pulled, both DRL's become inoperative, but the other high beam bulb will still work for the high beam function.

But the main oddity is that the DRL and high beam functions actually REVERSE THE POLARITY of the wires for each function. So for high beams, the blue wire gets +12V and the yellow wire is ground. But on DRL function (still full battery voltage), the yellow wire becomes +12V and the blue wire is ground.

So I'm not sure how the bulb runs at a dimmer level for DRL, when it's still getting full battery voltage.
 
wow....13v...now im confused again!!!

how do it do what it do??does it drop amperage to the bulb to make it play nice?

on a positive note: Now i dont have to worry about minimum voltage requirements for replay operation! Thanks Patrick!
 
@Luv2Lafmcc DRL UPDATE!!! I just put my multimeter across the high beam bulb plug to check the voltage. What I found was that the high beam bulbs receive FULL BATTERY VOLTAGE 13+ V (engine running) for both DRL use and high beam use. One oddity, though, is that when one high beam harness is pulled, both DRL's become inoperative, but the other high beam bulb will still work for the high beam function.

But the main oddity is that the DRL and high beam functions actually REVERSE THE POLARITY of the wires for each function. So for high beams, the blue wire gets +12V and the yellow wire is ground. But on DRL function (still full battery voltage), the yellow wire becomes +12V and the blue wire is ground.

So I'm not sure how the bulb runs at a dimmer level for DRL, when it's still getting full battery voltage.
Your finding on halogen high-beam/DRL's voltage is truely odd! The resistence on high-beam filament is a constant value no matter the polarity is reversed or not. Hence the dimmer level for DRLs could be the circuitry change from parallel to serial from two high-beam bulbs. This makes some sense as you pulled one bulb connector and both DRLs didn't work but the single high-beam worked in high-beam mode. In this case the bulbs in serial DRL mode still should show 6 volts each but in fact it's not?!

BTW, nice to see you posting again! :)
 
wow....13v...now im confused again!!!

how do it do what it do??does it drop amperage to the bulb to make it play nice?

on a positive note: Now i dont have to worry about minimum voltage requirements for replay operation! Thanks Patrick!

Will your relay be okay with the reversed polarity, though? I'm not sure how they would react. So for example if you have a relay that triggers when DRL is on, then when you turn the headlights on or put the car in park the relay would deactivate (no voltage), but then if you use the high beams, the relay would see reversed polarity voltage. I'm not sure if that could cause any damage or not. *edit* looking up Bosch relay info, it seems like the reverse polarity would be okay. But whatever you're controlling with the relay would activate with both the DRL and the high beams.
 
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