Driving Light Relays Question

Hi all,

I've searched the forum extensively to find some information. I have a 2001 Cherokee Sport and would like to add a set of driving lights, but of course I need them to turn off when I hit the highbeams or I will fail inspection. My search turned up this diagram -

My question is - can I alter this circuit so that I can have a switch to turn the driving lights on/off? In this diagram, they're on any time the parking lights are on.

If it helps at all, my truck has some wiring for driving lights from the factory, but not all. There is a harness behind where the factory switch would be, and I put a test-light on it today. Sure enough, when the headlights are on, one wire (the illumination feed for the switch, I presume) has power.

Here's a modified version of the relay setup:

You can use any +12v source(preferably headlight switch or ignition source) to the switch to power the driving lights.  You could use the factory harness illimination feed you spoke of.  That way, even if the switch shown is in the "on" position, when you turn off the headlights, the driving lights will go off also.

The switch shown can be any type of on/off switch you prefer.  It will carry a very small current load.  The relay on the right is for overall switching purposes only.  The relay on the left is the high current load to actually power the driving lights.  

96hawkcnvt wrote:

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Do you want to use your driving lights with the hi-beam on? If so, that ckt will not work. They will still turn off when the hi-beams go on.

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I want the circuit to turn off when the hi-beams are on. I wired the relays as instructed, and the lights are on only when the high-beams are on.

What could be wrong?

Recheck your wiring connections on the relay on the right.  The high beam connection never supplies power to the driving lights, it only switches the power off to them instead.  As 96hawkcnvt stated, you must have the 87 & 87a terminals wired incorrectly and/or the 30 terminal.

To simplify things, disconnect the high beam tap and get the driving lights to work using the on/off switch first.  Then connect the high beam tap and see if the lights go off when the high beams are turned on.

Recheck your wiring and post back with the results.

Guys, thanks for the help. I have checked (and re-checked) the wiring, and it is all OK. Here's what I've found:

When I disconnect just the high-beam tap, the lights do not come on at all.

I have used the switch on 87a and 87, and it made no difference; the lights were still on (only on high-beams).

I checked the FSM for the truck, and the high-beam tap wire would be 12v coming into the relay, will that affect how the relay switches?

Thanks in advance guys!

If the driving lights work with the high beam tap connected and not with the switch when the high beam tap is removed, then you still have something wired incorrectly on the relay on the right.

Yes, the high beam tap should be +12v.  When the relay on the right sees power to terminal 86 from the +12v from the high beam tap, it switches the connection from terminal 87a to terminal 87, which has nothing connected to it, so the driving lights should not be seeing any power, therefore, they should not be coming on.

Likewise, the +12v power from the on/off switch is a direct connection from terminal 87a to terminal 30, which routes the power to the relay on the left to activate the relay to power the driving lights.

If the lights do not work with the on/off switch, but work with the high beams on, then you still have something wired incorrectly on the relay on the right. Have you checked to make sure you have +12v coming thru the on/off switch?

I know you said you rechecked the wiring, but trust me, something is still not wired correctly. Humor me and recheck it again, pull all of the wires off of the relay on the right and start there from scratch again.

Post back with the results.

Hello again. Hoptup, I should have been more clear. What I meant was, the driving lights do turn on and off with the switch, but ONLY when the highbeams are on. When the parking lights or lowbeams are on, I have no driving lights. The switch does have 12v coming out any time it is switched to on.

Is it possible I have a bad relay? I will try another one that I found in the garage and see if that one works properly.

UPDATE: The lights are now working correctly. For kicks, I swapped in a known good relay and it's working fine.

Thanks again for your help Hoptup, your diagram was spot-on! Wow, nothing is more aggravating that installing new parts that turn out to be defective.

Its unusual that a new relay would be bad, but thats the kind of luck I usually have.  Its a good thing you had a good relay to swap in and prove that the new relay was bad, or I would have kept telling you you had it wired wrong and you would have kept telling me no you didn't!

I'm glad you resolved the problem and everything is now working!