87 vert fogs not working

[Ceeker]

Anyway, the exact scenario you mentioned in post 12 was fog light switch on, check control warning OFF until insertion of low beam fuses, and check control+dim low beams upon insertion. I get that right? What position was the headlight switch in? All the way out, or first click?

I will double check again and give my observations for both settings.

results -went through sequence test:

Headlight switch off---Fog switch on = Lows on dim. - no fogs

HL switch on half/park lights ---Fog switch on = lows on dim - no fogs
(K4 - light blue relay makes buzzing noise)

HL switch on full----Fog light switch on = Lows are normal. - no fogs
(K4 - light blue relay stops buzzing)


With the low beams on dimly, now that you know they go out with the fuses pulled, find out which relay(s) makes them turn off. K3, K4, and/or K8.

K4 relay -low relay buzzes but as soon as I remove K8 it stops - dim lows go out. - fog switch on
K8 relay -when I romove the dim lows also go out. - fog switch on

Also, which relays on your car have five pin sockets in the fusebox out of those three?[/quote]

K3 - 5 pin relay - chrome color - high beam relay

Will do. and let you know. thank you thank you for your patience and tremendous input.

[DaveSmed]

OK! I think I might have an idea. Pull out K1 and K6, and install them in place of K4 and K8. I think one or both of those has a standard terminal layout, and its backfeeding through the low beams.

BMW relays are special.

[Ceeker]

OK! I think I might have an idea. Pull out K1 and K6, and install them in place of K4 and K8. I think one or both of those has a standard terminal layout, and its backfeeding through the low beams.

BMW relays are special.

There are about 3 relays (light blue) of the same part number excluding K4K8 that share the fuse box. I think they all share the same pin config. I have to hit the garage so I'll go out now and swap to see what happens. Give update shortly.

Ok. I swapped out the relays as you instructed: no change with the lights on full -fog switch on or lights half way- dim - fog switch on. sigh..lol.

sheesh....the plot thickens..I've read some posts on here...you're pretty good at this stuff huh? (Grin)

[DaveSmed]

There are about 3 relays (light blue) of the same part number excluding K4K8 that share the fuse box. I think they all share the same pin config. I have to hit the garage so I'll go out now and swap to see what happens. Give update shortly.

Ok. I swapped out the relays as you instructed: no change with the lights on full -fog switch on or lights half way- dim - fog switch on. sigh..lol.

sheesh....the plot thickens..I've read some posts on here...you're pretty good at this stuff huh? (Grin)

Wait a sec, I think I figured it out! (somewhat).

If K4 is buzzing any time the lows are on dimly, that should be fixed by a relay with a diode in it. I'll attach a diagram, but when the fog switch is on, and headlight switch off, K4 and K8s coils are connected in series, with K8 grounding through the low beam headlights themselves. When that circuit ends up energizing K4, it supplies power to the headlights, removing the ground path through K8 to K4 causing it to de-energize. Once that happens it re-energizes and just keeps cycling.

Now, as to why your fogs don't work.... time for the usual suspects with that out of the way. Stuff like the ground in the housing, corrosion at the wire attached to the bulb, etc.

[Ceeker]

Wait a sec, I think I figured it out! (somewhat).

If K4 is buzzing any time the lows are on dimly, that should be fixed by a relay with a diode in it. I'll attach a diagram, but when the fog switch is on, and headlight switch off, K4 and K8s coils are connected in series, with K8 grounding through the low beam headlights themselves. When that circuit ends up energizing K4, it supplies power to the headlights, removing the ground path through K8 to K4 causing it to de-energize. Once that happens it re-energizes and just keeps cycling.

so I read this over a few hundred times and see if I understand. outside of the diode issue;

K8 is supposed to be grounded out through the k4 ground circuit path - hence no headlights and no fogs regardless of of whether fog switch on, right?
The relays/coils share the same circuit. but since K8 and K4 share the same ground and K8 isn't grounding properly it is thinking K4 is the circuit to be used and thus - dim lows come on.

so if the ground is fixed then the path of energy would restored to the proper circuit?

So would this mean a new diode in K4 would isolate the ground allowing the( k8 relay) fogs to come on only when it recognizes that K4 is active?


Now, as to why your fogs don't work.... time for the usual suspects with that out of the way. Stuff like the ground in the housing, corrosion at the wire attached to the bulb, etc.

I disassembled the fogs before installing and found no problem with the contact points on the bulbs or the wiring. Nothing seemed broken or burnt. the connectors to the harness were also fine. I can't speak surely about the connectors from the wiring harness.

[DaveSmed]

so I read this over a few hundred times and see if I understand. outside of the diode issue;

K8 is supposed to be grounded out through the k4 ground circuit path - hence no headlights and no fogs regardless of of whether fog switch on, right?
The relays/coils share the same circuit. but since K8 and K4 share the same ground and K8 isn't grounding properly it is thinking K4 is the circuit to be used and thus - dim lows come on.

so if the ground is fixed then the path of energy would restored to the proper circuit?
So would this mean a new diode in K4 would isolate the ground allowing the( k8 relay) fogs to come on only when it recognizes that K4 is active?

Correct, K8 And K4 share the same ground path through the headlight switch in the fully on position. (with K8 going through the fog switch first)

K4's coil is connected to constant power, so it is always looking for a path back to ground. When the fog light button is pressed, a path through K8's coil is supplied via the headlight bulbs themselves. This activates K4, which supplies +12v to the headlights, removing the ground through K8. That in turn deactivates K4, again grounding through K8. OnOffOnOffOnOff.... Bzzzzzz....... Hopefully my (poor) highlighting job helps make some sense of what I'm trying to say. "L" is continued on to the check relay and low beams.

Can't believe I missed that, even after thinking diode in post #8!! D'oh!

If you have another non-318 E30 handy (guessing so, with the facelift pic in your avatar?) Swipe the OE K8 out of it and give it a try, should solve that problem.

Now, all that being said, the relays in question should work as designed with the headlight switch on, diode or not. As you can see in the diagram, there really isn't much left to suspect if the fog light indicator on the dash is working correctly, you know at least the drivers side fog light is getting power...

[Ceeker]

you said:

Now, all that being said, the relays in question should work as designed with the headlight switch on, diode or not. As you can see in the diagram, there really isn't much left to suspect if the fog light indicator on the dash is working correctly, you know at least the drivers side fog light is getting power...

Well, you are correct! I installed a spare K8 relay and as soon as I put the low headlights on I got the drivers side fog to work. Now, we have to figure out why the passenger side doesn't..lol. I will go with a new bulb just to be safe and give you my update.

Update: drivers side works, passenger side doesn't. I switched bulbs to make sure -both bulbs good. Switched the fuse for passenger side 3 times still no right side fog. now what? LOL

Another update: Feb 6 2011

ok, I tested the right side with a light tester and found power is coming from the main harness. when I tested the harness to the right fog; I wasn't getting any power. So I tweaked the pin connectors and then probed the wiring and came live! when I hooked up the fog light I didn't get light from the fog. But I tested the the circuit anyway and found power going to both wires.

Because the fog light might be blown does this mean the circuit isn't grounded and ground is feeding off the power line? Is it strange or just me?
it seems when the bulb is installed in the housing and the power is plugged into the harness and the ground is plugged into ground why would I be getting power from both? I know the body of the light bulb grounds to the body of the light case. But why then would power transfer from the live side which is plugged into the harness over to the ground side. The light tested showed both wires live. I grounded the test light to somewhere inside the engine compartment. I bought a new bulb and installed it and still no luck.
My suspicion? I think somewhere along that 18 inch harness the ground may have broken. well at least I've narrowed it down. lol.

Feb 7: After testing the harness in various ways there doesn't seem to be a break in the line; this would suspect me to believe the ground connection from the main harness might be corroded or the pin connection contact may not be tight. I crimped the female connectors slightly for a better fit. Once I installed the fog light harness to the main harness for test, the light came on.

MISSION ACCOMPLISHED!!! wow, what a learning experience, and a great big thanks to you Dave for taking the time out!!!!!!!!!

I know who to come too the next time I have an electrical issue, speaking of which now I think about it. Going to start a new thread though under General tech look for rear fan defog.

We're getting there Dave. Thx.

Ern