Wiring Fog Light as DRL
 

I always use my fog lights as DRLs. I really would like to wire only the fog lights to be on whenever the ignition switches on. How complex would this really be? I can't imagine it would be that hard. I am relatively mechanically inclined, and know I could do it if I had the proper instructions. I would help as much as possible with pictures, etc to aid the process. I ONLY want the fog lights on when ignition is on, not the parking lamps (front or rear) or the interior lights. So I am not sure if I would even really need to access the actual light switch. Please let me know if I would be getting myself in too deep... I really would like to do this... and have a little project! ;) I almost wish my car would break down so I could work on it somehow!! I know that I probably just jinxed myself........

It would look like this with the "DRL" THANX!


http://www.a-p-group.com/cklasse/CFront.JPG


http://www.a-p-group.com/cklasse/Front.JPG
;)

test to find the wire that turns on the fogs, and wire it up to the ignition on position.

But I am sure there is a much better method involving relays and or fuses.

Alon

Well, I really thought you were in a mess here. But, after looking at the wiring diagram it would be rather easy. The fog lites come right off the light switch through fuse 8. They do not go through the Exterior Lamp Module as all other lights do.

There are no term 15 (switched hot) positions on the light switch so I would disconnect it and find a suitable term 15 to power it. If removed at the light switch the fuse will be between the wire and the lights, protect your insertion.

Yes, that kind of scared me too... what kind of relay would I use!? Wouldn't a fuse just be safe enough? That is what Steve was refering to, correct? Thanks John. :p


Exactly... and I don't need the parking lamps on either...

I really think the fog lights (independent of the headlights) with my grill really have an authorative look.

David,

A standard SPDT relay will work, I recommend BOSCH for all relay needs.

I would wire it so that terminal #30 goes TO the fog light bulbs. Terminal #87a will connect to the ORIGINAL wire from the light switch that operates the fog light normally. Wiring it this way, you will have "normal" fog light operation if the relay is not energized. So if the relay goes out, you still have the normal operation as a backup.

Terminal #87 will be the power terminal. This is the fused circuit from the positive battery post or other positive power point. I don't know what wattage bulbs you are using, but I would run a line directly from the battery positive post.

Terminal #85 and #86 will be for the trigger circuit. You can wire this portion up a number of different ways. You can tap the #87 for the power into #86 and then just ground #85 via a switch to turn on the lights.

But since you want the fog lights to operate like DRL and automatically come on with the ignition switch, I would find a circuit that gets power when the ignition is on and tap into that to energize the relay. Terminal #86 will be connected to this power and #85 will be grounded.

So when you turn on the ignition, #86 is energized and completes the circuit via #85. This triggers the relay and opens the #87a to #30 circuit and connects #87 to #30.... voila! your lights are on.

When the ignition is turned off, the magnetic field collapses and #87a and #30 are reconnected.

Hope this helps!

-David

John,

Thanks!

I'm glad it came out as clearly as it did.

I think BOSCH relays are well worth the small additional cost. I installed a set of Hella Air Horns on my 400e. I was surprised to see that they DID NOT use a Hella or Bosch relay, it was just some cheap generic SPST. Well 2 months after the install, I lost my air horn. Found that the relay was dead. I figured it was from the heat in the engine bay. Replaced it with a Bosch and have not had any problems since.

-David

David, (BTW, I love your name ;) )

Thank you so much for writing that out for me.
And thank you John Shellenberg for verifying those to be very good directions.

Would I just purchase a "convention" relay from Bosch!? What is the cost roughly? What would the purpose of this relay be? And one thing I need to get started... what are all of those numbers? 87, etc? Are those numbers for wire terminals in my car... or for the relay?

Thanks again guys.

David,

If you can't find a Bosch relay at your local auto store, you can order them online from www.partsexpress.com. They have Bosch 30 amp SPDT listed in their printed catalog for $1.99!!

As John explained, the numbers I referred to are the terminal numbers for the relay. Here is a good reference on relay's:

http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm


Good luck with you project and let us all know how it turns out. Just remember to pay close attention to all connections. Use solder and heat shrink tubing for strong professional connections.

-David

Ok, now the wiring.... where do I get it? What kind? Where do I get the heat shrink tubing? I will buy a soldering iron and these parts soon, and will keep you all updated with pictures and the like. Hope to get started within a few days.
Just called Pep Boys and Auto Zone, they don't have the relay by Bosch. I guess I'll get it from the link posted! Thanks again for the help guys.

And for terminal 86 (positive power), could I tap into something via the fusebox? The instrument cluster, per say? Or anything else that turns on with ignition 2? What about brake lamp fuse, etc? And are you saying I should just make an inline fuse?

How do I get access to the light switch for # 87? Through fuse box also? Through the fuse box for the fog lights also? Or directly to the fog lights....?

David,

Everything except for the Bosch relay can be purchased at Home Depot.

Here is a basic layout of what you will be wiring. Use is JUST FOR REFERENCE!:

http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/foglites.htm

DO NOT wire terminal #30 to the power supply as they showed. Use terminal #87 as I said in the previous post. This allows for normal operation due to any relay failure.

Follow my connections and you will be fine. For example, they use terminal #86 for the ground and #85 for (+). I use #86 as (+) and #85 for ground. This is the correct polarity for a Bosch relay. It will still work their way, but why not do it the correct way.

Most of your wiring will be in the engine bay. No need to tap into the light switch in the cabin.

Remember, a relay is just an electro-magntic switch. You are using a low current circuit to control an electrically independent high current circuit.

Since John will be helping with the connections, I'll let him help with the layout and where things will go. I don't know if he will suggest using 1 relay with the lights running in parallel or 2 relays with each controlling one light. If Bosch has a DPDT relay, this will make things cleaner and less wiring. I checked, but couldn't find a DPDT from Bosch.

Good Luck!

-David

David, you need to find the following wires:

1. Constant power. This wire will have power regardless of the ignition switch.

2. Fog light "activation" wire. It turns "hot" when the foglights are on.

3. Switched power. This wire has power only when the ignition switch is on.

4. Good ground.

You say I need a tester for these? Why can't I just find wires that I know what they are? For example, wires in the fuse box for the fog lamp, an ignition wire... (can't I just hook it to anything that will go on when the car is on? my cd player is hooked to the cig lighter...), a ground (anywhere), and a constant power... (?).

I am going to order the relay as referenced above. Then I will buy some wire. Can I just do this from circuit city (car audio wire)? If I am not mistaken, the whole 'system' of wires and the relay will be run directly around the fuse box, correct?
Won't I need an inline fuse too?

Thanks!