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Posted by: saigon71 Dec 15 2018, 01:27 PM

My fog lights don't work on either side. After trying different bulbs, I tested for power with a VOM - no power. Next, I swapped the fog light relay out with several others...still no power.

What are the next logical things to check? Do the fog light switches go bad?

Thanks.

Posted by: orangecrate Dec 15 2018, 01:39 PM

Everything goes bad eventually. Did you check your grounds? And the fuse?

Posted by: saigon71 Dec 15 2018, 01:46 PM

I checked the fuse, but not the grounds...thanks.

Posted by: orangecrate Dec 15 2018, 01:47 PM

Camh Ran Bay 70/71 USN

Posted by: DickSteinkamp Dec 15 2018, 02:32 PM

You are probably way ahead of me on this, but just to be sure...

The key has to be on and the headlights have to be on low beam.

Posted by: oakdalecurtis Dec 15 2018, 03:33 PM

Bet money that Dick is right, you have the high beams on. If you’re any good at electrical, rewire the fog lights to an independent switch and relay so you can operate them separately from your headlights. I use my foglights that way as daytime running lights.

Posted by: porschetub Dec 15 2018, 03:35 PM

Good points,you could check for voltage @ your fuseboard ,foglight relay pin #30 to at least isolate that as an issue then you know its further down the line,if that's ok it may be your switch but less likely.
Go well .

Posted by: Tbrown4x4 Dec 15 2018, 08:36 PM

Oh man. I have a '73 and the fogs only turn on when my high beams are ON. I always thought that was stupid. Who uses their high beams in the fog?

I plan on re-wiring mine to provide voltage to the fog lamp relay so I can use them independantly as well.

Posted by: ClayPerrine Dec 15 2018, 10:13 PM

JWest engineering has a kit to convert the fog lights to turn on without the headlamps being on at all.

Highly recommend this. I use the fogs as daytime running lights to help the idiots out there to see me coming.

Posted by: 76-914 Dec 15 2018, 10:40 PM

IIRC, someone posted a "work around" using a jumper or switching legs on the headlamp switch so you didn't need the JWest kit.

Posted by: DickSteinkamp Dec 17 2018, 07:34 PM

It sounds like they are set up to be used as driving lights...not fog lights. Did any 914s come with optional driving lights?

Posted by: JeffBowlsby Dec 17 2018, 08:09 PM

The euro market cars were driving lights. USA market cars, fog lights.

Posted by: porschetub Dec 17 2018, 11:50 PM

Done for safety reasons,in my country you can't have it anything different.
Would like the daylight setup but not an option for me bugger it.

Posted by: RickS Dec 17 2018, 11:55 PM

Replaced my useless fogs with drivers from 914 Rubber. Work great. Also didn’t need JWest Kit, just moved one wire to operate independently with the switch.

Posted by: Mark Henry Dec 18 2018, 07:14 AM

How to rewire you driving/fog lights.
https://members.rennlist.com/demick/fogrewire.html

Posted by: 76-914 Dec 18 2018, 12:52 PM

Ta Dah, that's it Mark. I bookmarked it this time.

Posted by: Spoke Dec 18 2018, 09:30 PM

Do your high beams work? If the one high beam that powers the fog light relay is burned out, the relay will never close and power the fogs.

Posted by: underdog Dec 19 2018, 10:28 AM

jwest no longer sells this module.

Posted by: cary Dec 19 2018, 10:47 AM

Ditto ..................... then you'll feel like a dumb ass. BTDT

Posted by: Mark Henry Dec 19 2018, 10:47 AM

Also linked to that page is the original Pilot light DIY fog light how to.

Posted by: saigon71 Dec 22 2018, 04:46 PM

Cleaned the grounds behind both headlights, no help.

Posted by: saigon71 Dec 22 2018, 04:48 PM

I was hoping this was the "problem" but it wasn't. Fogs don't work on low beams.

Posted by: saigon71 Dec 22 2018, 04:53 PM

I've got 12V at fuse #10 and foglight relay pin #30.

Posted by: saigon71 Dec 22 2018, 04:53 PM

Yes, high beams work.

Posted by: Porschef Dec 24 2018, 07:44 AM

Posted by: Mark Henry Dec 24 2018, 08:09 AM

Check the wire(s) to the lights for continuity.

Posted by: 76-914 Dec 24 2018, 11:16 AM

I chased a problem similar to this. The relay and it's rubber socket had passed voltage/continuity tests a few times. When moving the relay harness out of the way ( I was working on another problem at the time and had given up on that circuit) I heard it click and found that circuit now working. When the fuse panel was reconnected it quit working. I found that when that harness was in a "certain position" it did not function. The break was inside the rubber plug and when placed in that certain position it would break the connection. Otherwise it was good. Luck was with me that day.

Posted by: Spoke Dec 24 2018, 12:28 PM

12V at fuse #10 is good. #10 also powers the horn.

What voltage do you read at foglight relay pin 85? Should be 12V. This voltage comes from the foglight switch.

Once 12V at pin 85 is verified, check foglight relay pin 86. Pin 86 should be 0V with headlights on and on low beams. Pin 86 is connected to fuse #1/#2 which power the high beams.

Once 12V at pin 86 and 0V at pin 85 on foglight relay are verified, measure foglight pin 87. Should be 12V. Pin 87 powers the foglights.

Does the lamp on the foglight switch light up? Is the lamp on the foglight switch good?

Posted by: Spoke Dec 27 2018, 07:14 AM

Here's a simplified schematic of the foglight circuit for a '74 914 as detailed in the Haynes shop manual.

There are 5 main components in the foglight circuit:

o Foglight switch
o Foglight relay
o Headlight dimmer relay
o High beam filament
o Headlight switch

To operate the foglights, the following conditions must be met:
o The headlight switch must be in the headlight position (2nd click outwards)
o The headlight dimmer relay must be on low beams.
o The foglight switch must be pulled out.

With conditions above met, current flow for the foglight relay coil goes through the headlight switch -->> foglight switch -->> foglight coil -->> headlight high beam filaments. The foglight relay coil shares 12V with the headlight high beam filaments. With standard headlights, the high beam filaments are much lower in resistance than the foglight relay coil thus most of the voltage drop is across the relay coil and the relay closes and foglights are on.

If the headlights are high impedance LEDs, it is not clear if the foglight relay coil will energize. The foglights can be made independent of the high beams by removing the wire from pin 86 of the foglight and attaching it to ground bypassing the high beam filaments.



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Posted by: saigon71 Dec 27 2018, 07:41 AM

Fog lights are working again. I appreciate all the help. To summarize the problem,

I hereby charge myself with two counts of being an idiot:

Count #1: The original "problem" was due to the fact that I did indeed have the hi beams on and didn't realize the fogs only worked on low.

Count #2: Due to the "problem" discussed in count #1, I wanted to check the bulbs, so I popped the covers off. I left everything apart while troubleshooting. When the bulbs looked fine, I checked for voltage to the bulb and got nothing. I kept using the piece that holds the bulb for ground. The problem is that the bulb holder doesn't get grounded until the lens in installed.

I ended up busting a diode on a headlight motor during this ordeal so I added another item to fix while chasing a problem that didn't exist.