I have a 75 1.8 that I thought was having an issue with the fog lights. Until I realized that the reason the fogs weren't working while the headlights were on, is that the fog lights don't work with the high beams on.

When the headlights are turned on, I cannot switch off the high beams using the turn signal. The high beams remain on all of the time. It won't click on or off.

Any ideas? Is the turn signal arm possibly broken?

Bad hi/lo relay. The fog lamp relay gets its ground from the High beam hot. But only when the high bean is off. I beleive its a blue/white or white/blue attached to the high beam fuse. If you ground that wire the fogs will work with both high and low.

Thanks for the quick reply!