Electrical Gurus need diagnosis

[AshEvan]

From time to time, my headlights will not come on, until I get my 74 911 on freeway and bring rpm up to 5K in 3rd or 4th. Also turn signals blink 2x, then both come on and fade.

* All fuses replaced in Fuse box
* Wires in fuse box checked to make sure no loose screws
* Replaced headlight switch, and turns signal unit,
* Checked all wires under steering wheel to make sure non are loose/not connected, and relays grounded.

What else should I check?

[timmy2]

2 things come to mind right away:

1. Grounds, Grounds and more grounds... Especially the ones behind the battery negative post and in/near the headlight and turn signal housings both front and back. Remove, clean with emery board and replace.

2. You should get an inexpensive digital DC voltmeter and plug it into the lighter socket and see what your DC voltage output is doing when it is acting up. (Ebay or local flaps)

Could be a voltage regulator going bad or even your alternator as well. (Worst case scenario)

My lights would flicker and act strange when my original VR was going out on my car. Replaced it with a new solid state one and it has been fine since. (new battery too!) Alternator was/is fine.

[AshEvan]

Originally Posted by timmy2

2 things come to mind right away:

1. Grounds, Grounds and more grounds... Especially the ones behind the battery negative post and in/near the headlight and turn signal housings both front and back. Remove, clean with emery board and replace.

2. You should get an inexpensive digital DC voltmeter and plug it into the lighter socket and see what your DC voltage output is doing when it is acting up. (Ebay or local flaps)

Could be a voltage regulator going bad or even your alternator as well. (Worst case scenario)

My lights would flicker and act strange when my original VR was going out on my car. Replaced it with a new solid state one and it has been fine since. (new battery too!) Alternator was/is fine.

Thanks. Appreciate the post!

[docrodg]

Grounds or VR. Try a simple voltmeter as suggested above... plugged into the lighter circuit and then drive, look for dropping voltage. When a VR goes out they tend to allow the volts to drop with high Ampere draw.

[HawgRyder]

I have seen situations where the fenders are NOT grounded properly to the body!
Sometimes you need to clean a couple of bolts and their holes to get them to contact well.
Bob

[AshEvan]

[docrodg]

Nice looking car!

[AshEvan]

Originally Posted by docrodg

Nice looking car!

Thanks for kind words and solution ideas

[RDM]

I'd suggest some headlight relays as well. Take the switch out of the main current path and it will be less likely to develop troublesome behaviors.