Fog light harness question(s)....

Topic: Fog light harness question(s).... (Read 2076 times) previous topic - next topic

Fog light harness question(s)....

January 07, 2009, 11:45:05 PM

I'm planning on installing the new Hella lights tomorrow.I'm looking at the harness (new harness came with the lights)and can figure most of it out.Two plugs to the lights...check. one plug to the relay....check. One wire with a fuse to the hot side of the battery....check. One for ground....check. Now,I have one more plug that goes to the switch,but the plug won't fit any switch I've seen.There's 3 wires....yellow,black,and blue.Which wire is for what?I would guess black is ground (usually).The other two I don't now.I'll add clips to the wires and plug them to the switch.

Second question,there's a blue wire on the harness that is wrapped like the rest and off to it's own.What would that be for?

Fog light harness question(s)....

Reply #1 – January 08, 2009, 08:09:31 AM

If there's three wires for a switch one would be ground (for a lighted switch), one would be power input (from the battery) and one would be power output (to the relay). On a typical three-pr0ng lighted switch the top wire is ground, the middle wire goes to the relay, and the bottom wire goes to the battery. This configuration allows the switch to light up when turned on.

Fog light harness question(s)....

Reply #2 – January 08, 2009, 09:09:25 AM

Thanks Chicken.What do you think that the blue wire all alone in the harness does?There's a plug that goes to the relay.This blue wire as I stated,is wrapped like the rest of the harness,but it's out there by itself.I can't figure out what it would be.

Fog light harness question(s)....

Reply #3 – January 08, 2009, 09:11:37 AM

As far as the switch wires,I figure black is ground,usually is,blue hot and yellow to the relay then.I suppose I can try it and if it doesn't work,swap 'em.

Fog light harness question(s)....

Reply #4 – January 08, 2009, 09:28:46 AM

the only way to figure this out is to sit there with a meter and tone out the switch and draw it out. your going to need to have a bulb/socket to bench test it before hand using your car battery.

switches with an LED proviision can be confussing, working the switch into a relay configuration makes it worse.

does your kit come with a new relay or are you using a factory option existing relay on the car?

The last time I did this in bulk was for the army in iraq. the soldiers often would order IR / Spot / Go light kits and have us wire them up. I remember making a mistake on one the lead that had the LED but did not repeat that. I know i have a drawing in my "Buffalo quick ref Guide" i drafted up for DOD , ill try to dig it up. Im pretty sure its exactly what you are looking for and contains the relay / switch / lighting layout.

The problem is this information resides on my sony laptop now owned by my son. I recently deleted pretty much everything on my side of that computer so by luck there might still be a folder with ths information.

Fog light harness question(s)....

Reply #5 – January 08, 2009, 09:51:26 AM

Quote from: vinnietbird;250768

Thanks Chicken.What do you think that the blue wire all alone in the harness does?There's a plug that goes to the relay.This blue wire as I stated,is wrapped like the rest of the harness,but it's out there by itself.I can't figure out what it would be.

Are there five wires in the relay harness? If so that extra one is probably not used. Most relays have five terminals: 85, 86, 87, 87a, and 30. 85 and 86 are the coil terminals, the ones that energize the relay when you power & ground 'em up. 30 is usually the high current feed (connected to battery). 87 is the output to the fog lights and is only energized when the relay is energized. 87a is energized when the relay is NOT energized, and is not used in most applications (it's a useful terminal in many other circuits though - circuits that you want to break when you power the relay, such as an anti-theft/starter interrup system).

If that wire is the "87a" wire it is very important that you tape it up (or, better still, remove the terminal from the relay plug). It is hot any time the relay is not turned on.

Fog light harness question(s)....

Reply #6 – January 08, 2009, 10:04:52 AM

This is a stand alone harness.The relay has 4 pr0ngs on it,and the harness has a plug for each light,a plug to the relay,a wire with an inline fuse and a lug on the end (to hook it to the battery or power source),a ground wire with a lug on the end,then the small plug for the switch,but the plug won't work on the switch.The light kit came with a harness,new Hella lights,relay,and switch (plus fasteners).I'll try to grab a couple of pics.

Fog light harness question(s)....

Reply #7 – January 08, 2009, 10:36:33 AM

Pics of what I'm talking about...

#1. To the switch
#2. the lone blue wire
#3. To the battery with an inline fuse
#4. Relay and plug
#5. Ground
#6./7. to the lights

The harness...

The switch plug...

The blue wire....

Fog light harness question(s)....

Reply #8 – January 08, 2009, 11:20:30 AM

The blue wouldn't be so that the lighted switch dims...

Sort of like when hooking up a newer stereo, they have a wire that you can attach so the radio dimms when you dim you dash lights?

Just a shot in the dark for me.... I know nothing about electrical .

Fog light harness question(s)....

Reply #9 – January 08, 2009, 11:57:56 AM

This is strictly a guess, but I'd say the blue wire is a second, low current power wire - the switch feed. The relay would draw its high current power directly from the battery (the wire you've got labeled #3), but the switch feed would draw its power either from the low beam circuit (to make the fog lights work only with the low beam headlights on, as most vehicles are wired from the factory) or an ignition-switched power source (to prevent the fog lights from coming on when the key is off). That blue wire you see in the switch harness is probably the other end of the loose blue wire. The yellow wire in the switch harness would go either to 85 or 86 on the relay.

Here, I've done up a diagram to show you how it should be wired (I even included a factory style switch, since I'm sure you've got one :D). When the switch is on the blue and yellow wires would be connected together, which sends power to the relay's coil. The yellow wire is also connected to the internal bulb inside the switch, so it will light up when the switch is on:

Fog light harness question(s)....

Reply #10 – January 08, 2009, 12:08:29 PM

Well,I'm going to have to cut the plug off of the switch end and install the new clips to hook up to the new switch.The TC switch I had broke.No big deal,I can fit any switch into that spot.I'll hook them to the switch and see what happens.The wires to my relay have a plug already,so they only fit one way to the relay.That helps.It's been years since I hooked up lights like this.

Fog light harness question(s)....

Reply #11 – January 09, 2009, 03:11:14 AM

i searched for my diagram,, no go,, deleted and im not sure out to undelete a file anymore in what was refered to in the old days as doss shell. XP is something totally different. If i were given instructions on how to undelete, then I know for a fact i have the diagram you need.

Fog light harness question(s)....

Reply #12 – January 09, 2009, 07:02:31 AM

I'm patient.One way or another it'll come together.I installed the lights yesterday,but not the harness yet.I ran out of time.

Fog light harness question(s)....

Reply #13 – January 09, 2009, 11:51:59 AM

tc
when the switch is flipped , wouldnt that put the assumed low current blue wire power feed directly to ground?
can you lable the relay to show the location of 30, 85, 86, 87 ( i assume 87a is the non provisioned center part of the base)

vinnie
Is the switch a one, two or three position? i assume two., on/off.

I assume your plans are to use the factory existing fog lamp switch in your bird?

Fog light harness question(s)....

Reply #14 – January 09, 2009, 03:31:07 PM

Quote from: jcassity;250916

tc
when the switch is flipped , wouldnt that put the assumed low current blue wire power feed directly to ground?
can you lable the relay to show the location of 30, 85, 86, 87 ( i assume 87a is the non provisioned center part of the base)

On the relay, the black and yellow wires would be 85 and 86. The red wire would be 30, and the green would be 87. 87a is indeed the missing center terminal (which is probably actually present on Vinnie's relay, but there is no wire in the harness).

Good eye on the switch. I kinda skimped on the schematic for the inside of the switch. The terminal layout and connections are correct for the TC fog light switch, but the wiring inside the switch is slightly different than what I showed here. The proper wiring for inside the switch is shown below. The "wiper" in the switch, the piece that moves and makes the electrical contact, is always connected to the yellow wire that goes to 85 (or 86) on the relay. When turned on the wiper makes a contact between the blue power input and the yellow power output and energizes the relay, while also energizing the bulb inside the switch. When the switch is off the wiper makes contact between the yellow wire and ground. This essentially grounds both sides of the bulb inside the switch, and also grounds both sides of the relay coil (both 85 and 86 will see ground). Because both sides are grounded and the blue wire is isolated no power flows, so the fog lights (and the indicator in the switch) do not light.

Anyway, here's how the TC foglight switch is really wired inside: