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Discussion Starter #1
While investigating changing the light set up on my car (1975 Nuova Super 1300 with a grill and light set up like and older Giulia) I discovered an interesting situation. When the engine is running the headlights work fine. High beams and low beams both function on each side. However, when the headlights are switched on with the engine off, the lows are fine, but high beams only work on one side. Also, the 'fari' light on the dash does not light.

Of course, I tend to use the car with the engine running, so this does not seem to be a direct problem. I am curious, though, as to whether that result should be expected or if this might be indicative of something in the electronics being slightly off. I do not know enough about circuitry to understand what is going on. Anybody have any ideas about the cause and whether it should be a concern?

Any and all insight appreciated.
 

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My guess is that someone in the past has done some creative wiring on your car.
 

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My guess is that someone in the past has done some creative wiring on your car.
I don't have a better explanation. But I can't imagine how some mad electrician would have wired it. While mid-70's Alfas have separate fuses for all four headlights, both H beam fuses (and both L beam fuses) receive power through the headlight switch. In other words, it doesn't seem possible that the left high beam gets powered from the battery (as it should) while the right high beam gets powered through the ignition switch.

Might someone have added relays to your headlight circuits? And powered one off the battery and one off the ignition switch?

Flyersguy said:
when the headlights are switched on with the engine off, the lows are fine, but high beams only work on one side.
What happens when ignition switch is on, but the engine isn't running? In other words, does this "one high beam" condition happen when the generator isn't turning or when the ignition isn't switched on?
 

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Discussion Starter #4
Ed and Jay, thanks for your replies. The 'mad electrician' theory may have some weight to it. PO was my father, who was into engineering his own solutions at times. He posted frequently on alfabb (under the moniker Mr. C). I searched his posts and found an old one where he said he was planning on installing relays for the headlights. I have not found any additional relays in the engine compartment connected to the headlights, but I will look around some more, and maybe under the dash area too, and keep my eye open for anything that seems unusual.

The one high beam regime exists when the engine is not running; whether or not the ignition is switched on does not seem to make a difference. Just whether the engine is running.
 

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The one high beam regime exists when the engine is not running; whether or not the ignition is switched on does not seem to make a difference. Just whether the engine is running.
Now that is seriously strange. All I can guess is that:

- Someone installed headlight relays with separate relays for the left and right high beams. Each of those relays was powered from a different source.

- The "dark with engine off" headlight relay is powered from the generator upstream of the regulator. The "lit with engine off" relay is powered from the battery.

OK, here's another question: How does the high beam brightness look? Does the light that behaves normally become appreciably brighter when the engine is running. Does the light that doesn't come on glow even a little (when viewed in the dark) with the engine not running?
 

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Discussion Starter #6
So, I tried to check if the 'high beam off' light was lit at all in the dark, but both came on full strength this time. Really no idea what to think, but better than not working at all.
 

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Spiders and GTV's of that era used fuses 7, 8, 9 & 10 for the four headlight filaments. With the engine running and the lights on, try pulling one fuse at a time and report what happens. That may give us a clue to what is going on.
 

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Read somewhere that bad grounds can cause much strangeness in these cars. I have personally experienced very mysterious patterns of lighting malfunction that were fixed by cleaning up the ground connections.
Just a thought.
Mike
 

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Read somewhere that bad grounds can cause much strangeness in these cars.
Yup, I like that theory. When the engine is running, things are shaking, and a flakey ground (or connector) may make contact. When things are standing still, that same connection may be open.

The fact that the ignition switch has no effect on the light - just whether the engine is vibrating things - suggests an intermittant ground or connector. I'd begin by looking at the suspect headlight's ground.
 

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I had odd and inconsistent things happening until I made a concerted effort to find all the grounds and clean them up. I would make that one of your top priorities in troubleshooting this.
 

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I had problems with one of the four headlights in my Super not always coming on, turns out it must have been some slight corrosion on one of the spades coming off the light pot. It usually acts up right around inspection time :).

Kevin
 

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Discussion Starter #12
I have done a lot of checking of grounds over the past few months, though probably not complete. I will keep going with that. Every one I have checked was in pretty god shape. I think the PO did the same not too long ago, and seems to have hit them with some kind of dielectric grease to keep them in good shape. I just have to find the one that he didn't find, or the one that might be more vulnerable to the elements.

Kredden- I first discovered this problem right before I switched out an old pair Cibie bobis for some new Hella halgoen lights. So the problem existed through two sets of prongs pairing to the connector. I would assume something similar could happen if there was some corrosion on the connector, which I admit i did not clean well when I made the switch; lost the little straw on my can of contact cleaner, will acquire new can or straw and do the right thing in that respect, make sure all contacts are clean.

Thanks everyone for all the ideas; I will do some work this weekend and report back what I can.
 

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Discussion Starter #13
Realized that I never closed this one out: cleaned the contacts inside the pigtail where the bulb plugs in, and problem went away. I think that means we were all on the right track, a dirty connection somewhere. Thanks everybody for the help!
 
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