Vehicle spotlight relay cct

[08crd]

I have an SUV that I want to fit spotlights to. On checking the headlights have a constant 12v supply and the high/low beam switch, switches the ground(-).
What I would like to make up is a current sensing cct to operate the spotlights relay as it can't be piggy backed to the high beam supply as normal. Or maybe a cct that detects the volt drop across the high beam when it is on.
Any ideas

 

[Reloadron]

When you mention spotlights are you referring to what are commonly called fog lights placed lower on the front grill work? While it can likely vary from SUV to SUV the fog lights on both trucks we have are controlled by relays that include fusing. The fog lights will not operate when high beam is selected for the headlights. Additionally turning on the headlights or any other lamps, the high side of the lamps are switched through the relays and not the commons or ground.

If this is true of your system then taking advantage of the power to the low beam relay might be an option for the logic rather than current sense. Sensing current is not all that difficult (assuming a good lamp) but does get a little involved.

Ron

 

[SABorn]

I think Ron has it a little backwards as in this country and many others, spotlights or driving lights (fog lights) are by law to be only on when high beam is on and switch off when the lights are dipped to low beam.

I recently fitted a set to a late model 4x4 for a friend and it gave me some grief getting it all working correctly, as on first wiring i used the negative to the high beam to trigger the spot light relay coil, this worked but it also activated all other parking lamps when the spotlight switch was on and the light switch was off........Hmmm not good!!

After much checking with a meter and lots of head scratching, the solution was to take the positive for the relay coil from the headlight circuit and the relay coil negative from the high beam circuit.
This solved all problems and works fine.

The 4x4 i worked on had the positive switched to the head lights via the lights on/off switch and the negative to the head lights switched via the dip switch, which is what i think is most likely also the case with your SUV.

Pete.

 

[Reloadron]

Hi Ya Pete

This is strictly an Equator thing. See since you are down under things are backwards. Seriously, here in the US and I believe Canada it is exactly the opposite. The fog lights will only operate when the low beams are on. Turning on or switching to high beams will disable the fog lights for the duration the high beams are in use. That being specific to factory equipment installed lights. I believe the UK actually has laws governing their use. Here in the US I am not sure how the law defines their use other than by jurisdiction. Anyway, from the factory on two GMC Yukon SUVs they work as I mentioned so go figure?

Ron

 

[SABorn]

Hi Ron,

Guess it makes sense as you refere to "fog lights" which we all know high beam in fog just makes a wall of light and visiabilty worst.

Here we use more driving lights or spot lights that are super bright and shine down the road for miles so we can see those pesty kangaroos and other wildlife, any on coming traffic have their eyeballs burnt out by the blinding light if they are not switched off during low beam.

Pete.

 

[08crd]

Thanks for your reply Ron, but as pete said over here in Australia we tend to use spotlights with our highbeam to detect things that go bump in the night.
Thanks pete for the idea, that may work if I pick up the positive from the low beam which is on both low and high. Then run the negative to the high beam negative, I will give it a go tomorrow and let you know how it goes.
By the way it is a late model Jeep typical, funny way of doing things.LOL

 

[alec_t]

Can't you just connect a relay coil directly in parallel with the high-beam filament so that the relay is energised (and its NO contact can switch on the spotlights) whenever high beam is on?