87 vert fogs not working

[Ceeker]

So I find out my car has an integrated low beam check system that is integrated into the circuit board under the fuse box. Every time I put my lows on the light in the check panel comes on. Lights work fine. I can live with this.
However; since I installed the factory fog lights and plugged them into the pre-wired plugs something odd happens.

when I put the fogs on the green light in the dash comes on. but no fog lights. when I put the parking lights on and put the fogs on the low beams come on dim. But still no fogs.

I checked fuses; I checked relays. Both my low and fog light relays are the light blue ones. I swapped them to see maybe it was the relay.

any help would be appreciated. Thx.

[DaveSmed]

Hmm, that's a new one.

First item is since the dash indicator works, there's power at least at the fuse and that whole circuit is not being pulled to ground.

If you happen to have a meter handy, pull the drivers side fog light apart (leave the bulb connected). With the green light on, and the meter grounded somewhere on the chassis separate from the fog light, bracket, bumper, etc. check for voltage at the positive lead coming in the housing, and the metal housing itself.

[Ceeker]

ok kewl..thanks. bit chilled right now -15 -23 degrees..brrrrrrr...

[DaveSmed]

Yikes, can't blame you there. I'm too much of a wuss to work on my car because its a nice warm 20deg outside.

[Ceeker]

ok, I looked a wiring diagram/schematics from Bentley, and it shows there is a high beam dimmer relay or switch located somewhere. Not to be confused with the dimmer on the headlight switch for the interior. I didn't test the fogs yet as suggested but I am wondering where it is and what this switch does? I threw some pics up. The part is in the left of both diagrams

[DaveSmed]

Thats the nomenclature they use for the switch on the turn signal stalk.

[Ceeker]

Thats the nomenclature they use for the switch on the turn signal stalk.

the WHAT???? LOL

What I am thinking is the headlight switch and fog light switch are sharing the same ciricuit or power supply for some strange reason or perhaps thsi is what it is supposed to be. the low beams come on like clockwork every time with the fog light pressed in. but they come on at about half intensity. Turn off the fog switch lights go out.

[DaveSmed]

Heh yea, random $10 word.

Anyway, the two switches control the lighting via ground side switching. One interesting thing I see is the fog light relay is supposed to have a diode in it (the only relay like it on the car). I think its to prevent the fog light relay from engaging when the button is in, headlights off, and the dimmer in the high beam position.

There really shouldn't be any way for the lights to come on dimly. You mentioned you are working on an 87, is it still a sealed beam car?

[Ceeker]

yup sealed beam car. :-) 87- so do you think the diode may be faulty not allowing the switch over???

[DaveSmed]

I'm actually thinking a screwed up ground up front somewhere.

When the lows come on dimly, does pulling a highbeam or fog light fuse turn them off?

[Ceeker]

I'm actually thinking a screwed up ground up front somewhere.

When the lows come on dimly, does pulling a highbeam or fog light fuse turn them off?

I think I tried this once already but will do it again to make sure. it's a balmy -20 degrees today with the wind chill this morning was more like -35. HOLY CRAP BATMAN!

[Ceeker]

ok, I noticed something interesting; lately my check panel hasn't been going off telling me my lows are out when in fact they are on. Then I removed the low beam fuse and put the fog light switch on. I got nothing. When I re-installed the fuse; the car began to give me the check control error like clockwork with the lows on. This leads me to believe either the fuse isn't making a good enough contact and sending a false signal. I still cant figure out why the wiring for the fogs is connected to the lows. The whether is warmer now so when I get some time I am going to first test as suggested from the fog light lead for power and then go from there. I don't think it is a harness or ground issue. why? the fogs should come on with the lows but they seem to be sharing the same circuit which tells me it might either be coming from the relay side or the check control circuit located below the fuse box. Since earlier models seam to have this feature integrated into the circuit board unlike the later models that have a relay.

the check control feature that I have is known to give false reading with the low beams. It's only the lows that are integrated with the circuit board.

[DaveSmed]

...Then I removed the low beam fuse and put the fog light switch on. I got nothing. When I re-installed the fuse; the car began to give me the check control error like clockwork with the lows on.

Ah ha, now we are getting somewhere.

This happened with the switch in the parking light position?

Take a look at the below diagram, and consider power going backwards through fuses 13 and 14. That would explain that behavior exactly.

How does the car behave with the high beams?

[Ceeker]

ok, this diagram seems to be a late model because you have the active check control unit as a separate relay. now I don't know if this actually makes a difference or not so I'll just go along. :-)
My lights seem to work fine with or without highs on. All 4 lights come on with the high beam stalk and the highs go off without. The only issue is the above head check panel. as soon as I put the lows on it comes on. when the parking lights are on I don't get this. When the lights are on with the lows or highs fog lights are inoperable.
When the parks lights are on the low's come on with the fog light switch.

If you had to guess, for sake of arguement the circuit board under the fuse box is good. What would the issue be with the low beam check control? relay?? I swapped the high and low relay out since they are both the same part #

[DaveSmed]

It shows it that way, but every year has it on the circuit board. From my '84, my '87, to my '92. The relay wiring is what really changes, and surprisingly, the ETM is not %100 accurate. FWIW though, that pic is from the 1987 ETM from BMW.

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?

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.

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