You can look at your back issues of the Registry magazine - an article on headlight circuit operation was in volume 38-5, 1-2/2015 starting on page 74, or go to the on-line version
https://porsche356registry.org/system/m ... 1431541784
Troubleshooting the headlight circuit was in the following issue - 38-6, 3-4/2015, page 64, also available on line.
https://porsche356registry.org/system/m ... 1431541885
Headlight low beams quit working
- Greg Bryan
- 356 Fan
- Posts: 3692
- Joined: Sat Oct 04, 2008 1:05 pm
- Location: San Pedro, CA 90732; Fallen Leaf, CA 96150
- Contact:
Re: Headlight low beams quit working
Greg Bryan
- Dave Wildrick
- 356 Fan
- Posts: 1953
- Joined: Wed Mar 26, 2008 2:10 pm
- Location: Houston, TX
Re: Headlight low beams quit working
Low beams:Dave Wildrick wrote:I have not done this yet.Larry Brooks wrote:Interesting. Have you tested your line voltage with the engine running at 2000rpm? An obvious place to check would be the headlight circuit.
I'll check and let you know.
6.4 V at idle (750 r/m)
7.2V at 2,000 r/m
Dave Wildrick
Houston, TX
#10230
64C coupe
65C coupe
Houston, TX
#10230
64C coupe
65C coupe
-
- 356 Fan
- Posts: 1260
- Joined: Thu Feb 05, 2009 8:13 pm
- Location: Texas Panhandle South Plains
Re: Headlight low beams quit working
"3.Maybe your car experienced some shock or vibration that caused the hot low beam filaments to fail while the cold high beam filaments weren't affected."
...did you drive on Oklahoma roads?...
...did you drive on Oklahoma roads?...
Mike
- Dave Wildrick
- 356 Fan
- Posts: 1953
- Joined: Wed Mar 26, 2008 2:10 pm
- Location: Houston, TX
Re: Headlight low beams quit working
Yes, but not with the headlights on.Mike Horton wrote:"3.Maybe your car experienced some shock or vibration that caused the hot low beam filaments to fail while the cold high beam filaments weren't affected."
...did you drive on Oklahoma roads?...
Dave Wildrick
Houston, TX
#10230
64C coupe
65C coupe
Houston, TX
#10230
64C coupe
65C coupe
-
- 356 Fan
- Posts: 1260
- Joined: Thu Feb 05, 2009 8:13 pm
- Location: Texas Panhandle South Plains
Re: Headlight low beams quit working
Cessna Citation jets have the landing lights mounted on the landing gear struts, and the vibrations transmitted from rough runways, and stiff tires, lead to short bulb life... with those, occasional replacement, was not uncommon...
...we could turn the filiments vertically, and get better life,
...we could turn the filiments vertically, and get better life,
Mike
- David Jones
- Classifieds Moderator
- Posts: 7323
- Joined: Tue Mar 25, 2008 6:32 pm
- Tag: I wish I knew as much as I think I know.
- Location: Kentucky
Re: Headlight low beams quit working
From the Instrument engineers handbook and from the recesses of my memory the following.
Shock and vibration, a low-voltage, high-current design should be used because it has strong filaments. Lamps of 6 volts or less usually have short, thick filaments, whereas lamps of more than 6 volts generally have longer and thinner filaments.
Shock and vibration, a low-voltage, high-current design should be used because it has strong filaments. Lamps of 6 volts or less usually have short, thick filaments, whereas lamps of more than 6 volts generally have longer and thinner filaments.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715
Cymru am byth
David Jones #9715
- Jim Alton
- 356 Fan
- Posts: 1772
- Joined: Sun Mar 30, 2008 12:11 pm
- Location: Los Angeles County
Re: Headlight low beams quit working
True. 6 V filaments should have twice the cross section of 12 V filaments (6 V filaments should have 1.4 times the diameter of 12 V filaments). It's not a likely failure but if both filaments really did fail simultaneously it has to be considered.David Jones wrote:From the Instrument engineers handbook and from the recesses of my memory the following.
Shock and vibration, a low-voltage, high-current design should be used because it has strong filaments. Lamps of 6 volts or less usually have short, thick filaments, whereas lamps of more than 6 volts generally have longer and thinner filaments.
Maybe--somehow--the car managed to vibrate at a resonant frequency for the filaments.
I'm guessing though that it's far more likely one had been out for a while but unnoticed.
Jim Alton
Los Angeles County, CA
1958 Porsche 356A Cabriolet
1965 Porsche 911 Coupé
1966 Volkswagen Type 2
2003 Porsche 986 Boxster