1979 E21 Fog Light Install Issues

[csvnevada]

Installing a set of used rectangular Hella fog lights on my 1979 E21. They don't seem to be working correctly. Here are some of the symptoms.

Sometimes the low beam headlights will come on when pulling headlight switch to halfway position (parking light) with key off and sometimes only the right fog light will come on and no low beam headlights. With key on accessory position low beam lights are on when fog light switch is activated but no fog lights on. With key fully on and headlight switch is activated for parking lights as well as full on position all lights are on except left fog light. When high beams are on fog light on right stays on. When I first hooked up the fog lights the left fog light was on briefly but may have burned out. The fog light dash switch doesn't seem to turn the fog light on or off.

My early version E21 never had the optional fog lights installed. I installed two fog lights using the existing wiring that was already in place. I had to install a factory dash push button (lighted) switch with the three unused wires with plugs from under the dash (yellow, gray & brown). Found the plugs at each headlight for the fog lights behind the black plastic access covers. Plugged each fog light into these plugs and ran a ground wire from each light to the system ground at the battery box. The fuse box already had a left and right fuse for each fog light and one relay for both fog lights according to the fuse box cover labels. In other words I installed the lights in what I thought was a logical sequence with the existing wiring and fuses/relay. No sign of previous owner doing any modifications to the wiring harness.

Does anyone have any ideas on what I did wrong or has anyone had problems installing fogs with the factory wiring? Any help would be appreciated.

/s/ CSV

[runsub5]

Installing a set of used rectangular Hella fog lights on my 1979 E21. They don't seem to be working correctly. Here are some of the symptoms.

Sometimes the low beam headlights will come on when pulling headlight switch to halfway position (parking light) with key off and sometimes only the right fog light will come on and no low beam headlights. With key on accessory position low beam lights are on when fog light switch is activated but no fog lights on. With key fully on and headlight switch is activated for parking lights as well as full on position all lights are on except left fog light. When high beams are on fog light on right stays on. When I first hooked up the fog lights the left fog light was on briefly but may have burned out. The fog light dash switch doesn't seem to turn the fog light on or off.

My early version E21 never had the optional fog lights installed. I installed two fog lights using the existing wiring that was already in place. I had to install a factory dash push button (lighted) switch with the three unused wires with plugs from under the dash (yellow, gray & brown). Found the plugs at each headlight for the fog lights behind the black plastic access covers. Plugged each fog light into these plugs and ran a ground wire from each light to the system ground at the battery box. The fuse box already had a left and right fuse for each fog light and one relay for both fog lights according to the fuse box cover labels. In other words I installed the lights in what I thought was a logical sequence with the existing wiring and fuses/relay. No sign of previous owner doing any modifications to the wiring harness.

Does anyone have any ideas on what I did wrong or has anyone had problems installing fogs with the factory wiring? Any help would be appreciated.

/s/ CSV

I installed Hella fog lights on my '79 38 years ago. The lights came with a toggle switch instead of a lighted push button, but this should not be the problem. Have you checked the ceramic fuse for the light that is not coming on. These fuses are notorious for not making good contact between poles. Could also be a bad ground which is causing the intermittent lighting problems. As for the wiring, I can't remember exactly what I did. The relay was already installed on mine as well. The car is currently in storage for the winter and I won't have access for a few weeks. Otherwise, I would check the wiring on my car to see if you wired it the same way. Sorry I can't be of more help.

[csvnevada]

Dave

Thanks for the reply. Will double check the fuse for the left light and may have to replace the bulb. Have tried a different relay and made sure the ground is clean (Actually used the same ground that the primary wiring harness is using at the bottom of the battery tray). Currently at a loss and hopefully someone may have had a similar problem and will be able to give me a clue to what is going on. Thanks again.

Sincerely,
/s/ CSV

[Jeroen]

Funny situation indeed, but at least it sounds like something is wrong with the left fog light, indeed like bulb or ground. The fogs should at least be switched together. Could the relay be behaving erraticly? Corroded fuse?

[csvnevada]

Will continue to try and find the problem. Ordered a new H3 bulb for the left side so when it arrives I will continue on. Looking at the Haynes USA wiring diagram so I can trace the wiring to see if there is a problem at the relay or fog light switch. Some of the wiring colors don't match my USA E21 but the diagram does give me an idea how the fog lights are wired from the factory. Thanks Jeroen for responding. If I find the problem I will post what it is.

Sincerely,
/s/ CSV

[Jeroen]

good luck!

[csvnevada]

Finally gave up on most of the factory fog light wiring on my 79 E21. The factory did not wire in the fuses and I never could figure out the headlight circuit. Rewired just about everything, but did tie the new wiring into the factory fuses, relay and used the original gray wire from the fog light dash switch/button to the relay. Eliminated the circuit that was tied to the head light switch and the pair of wires behind the front grill at the headlights. The fogs now work independently of the headlights. Fogs will only work when the ignition switch is on but can be operated with the dash switch/button when the headlights (low and high beam) are on or off. I am happy with the results but there was more work involved than what I was hoping for. /s/ CSV

[Jeroen]

Sounds like a hell of a job indeed but in the end you got it all to work, and like you want it to work. On to the next project!