I have a 1992 k75 low seat bike. I recently found a pair of halogen fog lights and brackets that were an option around 1986 for the k models back then. They are rectangle in shape and I have seen a few pictures in old brochures advertising them as an option. Does anyone know if there is some connecter on my bike that bmw may have left in the wiring harness that I could plug them into on my bike? I would like to change the original bulbs out to led light bulbs as well. Thanks

Taking this from the top and making no assumptions about your electrical knowledge:

- the lights and brackets might be in good shape but the reflectors will be completely shafted. Around that period the reflectors lost 60% of their reflectivity within four years of manufacture, so you might want to consider replacing the internals

- don't fit LEDs. They will not sit at the correct focal length for the reflector and will either blind oncoming traffic or will have a completely useless beam spread

- fuse 4 is a good option as it's not normally used but you may have problems sourcing the terminals. They are available but usually only in quantity, so your best bet is a fuse on a cable

https://www.ebay.com/itm/5-x-Inline-Fuse-Holder-12V-30A-DC-For-Standard-Blade-Fuses-Splash-Proof-Car-Bike/133113858785?hash=item1efe344ae1:g:~f4AAOSwSHBdLetm).

Alternatively, you can fit a 4-way fuse box next to the existing seven-way box. There is room to surface-mount one (Charlie!!! Didn't you have some pics of this idea?)

- use a four pin relay to wire them in. Work as follows:

-- one end of the fuse to the battery
-- other side to pin 30 on the relay
-- pin 87a on the relay to a toggle switch mounted somewhere up front e.g. on the 'crashpad'

https://www.ebay.com/itm/On-Off-SPST-Toggle-Switch-250V-AC-15A/282558340886?epid=9004679011&hash=item41c9ca1f16:g:6K0AAOSwOMdZXNox

-- other side of the toggle switch to the bulb-holder positive on the lights
-- check the earth for the lights. It might go through the brackets or you might have to add a wire. If so, use a brown coloured wire that will take a minimum of sixteen amps and run it to the earth point under the tank
-- pin 85 on the relay also goes to earth
-- connect pin 86 on the relay to the slate (grey)/black wire that runs to the tail light
-- use a 15 amp or even a 20 amp fuse. 50 watt halogens draw 4.16 amps (watts / volts = amps: (50 / 12 = 4.16) x 2 = 9.32 amps). Although that is less than 10 amps, the inrush current to a cold filament will easily exceed ten amps and will blow a 10 amp fuse.

The end result (hopefully!) is that you will have a toggle switch to turn the lights on/off and a relay that will cut the feed to the lights when the ignition is turned off. No little monsters walking by and flattening your battery.

Fusebox terminals if you want to use fuse 4 instead of a separate fuse/fusebox:

https://www.ebay.com/itm/High-Quality-Durable-50Pcs-4-8mm-Female-Copper-Fuse-Box-Terminals-N-907-327-03/253961449770?hash=item3b2148312a:g:FSkAAOSwb8Vb3AQO

Thanks Dai! I just need to source the light inards now.

Unless you are totally committed to OEM parts on your bike, I would suggest the following if you want to add driving/conspicuity lights.  

Get an Eastern Beaver headlight relay wiring harness.  It bypasses the handlebar switches for the high current of the headlight.  This protects the rather delicate switch contacts from overheating damage as they age and gives a brighter headlight.

Since the Eastern Beaver harness only runs a few milliamps through the switches to power the relays in the harness, you can now easily add LED driving lights by tapping into the bike's handlebar headlight switch wiring.  

A single pole double throw switch with a center off position will allow you to have the driving lights on all the time(daytime), off, or only with the high beam(used at night to avoid blinding oncoming drivers).

I get my driving lights on eBay.  There are lots of them there, and they are quite reasonably priced.  The last pair I got were $18 with free shipping.  Most have 10W LED's that draw less than 1 amp.  Get the spotlight beam pattern to throw the maximum light down the road.

+1 on the Eastern Beaver kit. Very noticeable improvement plus uplift in switch longevity.

But do note the import duty from Japan.

At the same time I added the EB 8 way auxiliary fuse box to make all my toys switchable.

I have done the Easteren Beaver headlight relay kit. I bought the one with a terminal to add driving lights. Hopefully I could tie into that and keep the fog lights halogen bulbs? I also am installing the Eastern Beaver fuse block (PC8)? as we speak. I am adding a pair of led lights that I did buy on ebay. I'm running the E.B. headlight relay kit through it along with a gps, radar detector and an extra power outlet. I have done the 50 amp alternator upgrade. All of this through help on this forum. Hopefully I don't cook my bikes electrical. I've been getting it ready to do a cross country trip. Am I overloading my electrical system? I added heated grips about 2 years ago per ducks guidance. Want to use these oem lights for daytime conspicuity. 

I’m running standard halogen in the head but an LED strip in the running light.

My GPS runs off fuse 6 in the OEM in place of the Clock.

From the EB fuse block I run:

1 LED spot on the chair
Heated grips
Heated socks
1 LED fog at the back
1 volt meter
2 USB ports - normally charging Phone and tablet.

This stuff is all switchable from the crash pad rockers. The EB block is wired into the rear light (UK bike, no full time running lights) so the switched fuses are triggered through the OEM sidelight switch on the bars (everything on the new circuits can be isolated with a single action).

I also use a 50 alternator, but tbh I never really got close to stretching even the OEM 

It’s prudent to list all the kit you have and work out your max simultaneous load, but I don’t think you’ll have an issue.

Like you, if it wasn’t for this forum I’d just be in the shed polishing the wheels...

I found a brand new set of the auxiliary lights that includes the switch and wiring harness. Both lights do work. The harness has a plug that fits into what is called  the Plug connection special equipment. It is in the electrical box under the seat. When I plug it together though only one light works. 
 My question is, should the auxiliary light harness plug work correctly with the Plug connection special equipment port? 
 I apologize for the complicated wording. In the wiring diagram they call this port: Plug Connection Special Equipment. Thank you

The lamps should differ in output. One should be a high beam; one should be a flood beam. Which is working and how did you test both of them? Have you checked for current at the relay box connector pin of the non-working light? How many sockets does the light assembly's plug have? Please post a photo of it.

The plug that comes with my harness has 4 female pins in it. It has 2 relays. It also has an oem light switch that I can place in the dash along with the hazard switch and heated grip switch. The Plug connection special equipment has 5 male pins. Both lights have been tested and both work. I plugged each light in the wiring harness that has 2 terminals, 1 for each light. Both would work in one side of the harness, but one terminal in the harness that allows you to plug the lights in has no power. I apologize for not posting pictures. I don't have that ability right now. I want to use the oem switch. Do I need 2 relays? I do have the Eastern Beaver Fuze block and have updated my headlight with the Eastern Beaver Headlight harness. I purchased the E.B. headlight harness with the extra auxiliary light wire. Thank you for your consideration with this issue.

Your K has a free  plug in the relay box dedicated to options such as additionnal lights.
Why not simply use it?

Yes it does and I connected to the Plug connection extra equipment port, however only one light will come on. The switch works but I can only get one light to come on. I've tested both lights and they both will come on when I switch the light terminals. I'm just missing something and can't quite get it. In my previous post I tried to share with my limited electrical knowledge.

After searching some other posts here I have the auxiliary lights running properly I believe. It's 3:15 am here and while searching the headlight upgrade post there was an explanation of the Plug connection special equipment connector. When I plugged the lights in only 1 light came on (fog lamp) however the other lamp (driving lamp) didn't come on, that was until I flipped the high beam on, then the fog lamp went out and the driving lamp came on.   I am elated that they operate now. If you've read any of my earlier posts I've been trying to figure this out for awhile. Had I flipped my hi beam switch on 3-4 days ago when I was wrestling with this I would have been done. Oh well, nothing like the learning curve with success. 
 I have a ton of gratitude for those who have helped and guided me on this forum. Thank you all so much for all the insight and now Goodnight.