68 Ghia H4 Headlight issue

[bdkee]

Hi all,

I've got a '68 Ghia coupe that I did the Hella H4 conversion to about a year ago. All has been well until recently the low beam on the passenger side went out. I've changed the bulb and it still isn't lighting. The high beam functions properly. The driver's side functions properly in both low and high beam.
I pulled the plug on the passenger side headlight bulb and with the switch (turn signal lever) in the low beam position tested the power wire. Testing the power and ground wire by themselves without the bulb I get 12v. With the power wire plugged into the bulb and the ground wire disconnected I get 12v on the bulb's power terminal (again using the ground wire as my ground for the volt meter). When I plug the ground wire into the back of the bulb it immediately looses voltage and the powered terminal drops to 0v (hence there's no light).

Using the same ground wire and with the brights turned on at the turn signal lever the bulb is powered and the brights work.

The fuses are all fine. Any ideas? Thanks all.

Brian

[Marfa61KG]

I'm not sure how your 68 wiring differs from my 61. Since you get 12V with no load and 0V with load, it appears that you have a very weak connection somewhere in your circuit. You have very high resistance somewhere.

Check your fuses again and perhaps polish up the contacts for the fuse and the fuse holder. Then check your connections on the wiring terminal behind the fuse block.

If you turn on the low beams, you should be able to check for voltage along the path until you find the bad connection. For example, do you have 12V on both sides of the fuse? On the wires going into and out of the fuse block? Into and out of the switch. It should be an easy bit of sleuthing. Follow the wire until you find the 12V!

[bdkee]

Thanks Marfa61KG. I'm off to sleuth. I'll post any progress.

Brian

[bdkee]

You're a genius Marfa61KG!! Some sand paper to the fuses and the panel and "Let there be light"!!

Cheers! That'll make the next beer a lot tastier.

Thanks.

Brian

[Marfa61KG]

Ha! Glad that helped. I've had the same problem. I replaced many a good bulb when I first had my Ghia. By the way, I've also got some H4 in my Ghjia. I know the lens is flatter and doesn't look as nice, but the light is incredible and much safer. I'll add relays at the bulbs sometime to get even brighter.

Rob

[Eric&Barb]

Add a little dielectric grease to each to the those fuse to fuse box connections to keep oxygen and corrosion away for as long as possible. Same for any 12 volt connection in your wiring.
_________________
In Stereo, Where Available!

[swavananda]

This is a great article on how to improve the headlight circuit. By adding relays you bypass the voltage drop at the switch. A wonderful mod for any night driving vw's.

http://www.danielsternlighting.com/tech/relays/relays.html

[helowrench]