Headlights stay ON

[PMCS Rally]

I am getting closer to finish may 17-year project of '72 4-Door and I need an advice.

Wiring is almost done (stock) and everything is working fine except headlights. With Ignition and light switch OFF when I connect the plug to headlight, it turns on. I know "always hot" wires from fuse to headlight so I traced "RED grounding wire" to 6-pin connector of JIDECO Relay 25230-89915. Check the continuity of the particular relay terminal and is grounded. Is this normal? I opened the relay and it was very clean and the terminal is "normally closed" position. Should I trace further to the light switch? Is my relay bad?

[510rob]

Here is a simplified sketch I made of the headlight wiring in a 510. It might help you troubleshoot your issue.

[icehouse]

Do you have oldschool H4 headlights?

[PMCS Rally]

Thank you for you information.

Yes, I have Cibie (and Hella) Halogen H4. Does it require any modification? Back in old days I remember it was simple swap of plug-and-play.

After reading your post, I tried with 2-prong Philips sealed beam laying around on low beam connector and it worked with light switch but by unknown reason it burned its filament almost instantly.

[datzenmike]

Some replacement headlamps have a grounded outer metal case and will stay on. I used strips of electrical tape to cover the tabs that align the lamps.

[PMCS Rally]

I see...will take a look at lamps.

[PMCS Rally]

I see...will take a look at lamps.

[PMCS Rally]

I think it was not the case. I removed the lamp totally from the body but it still stays ON.

[icehouse]

Gotta remove all the headlights/unplug. Some of those old H4 lights were metal on the back and the ground sneaks through the housing. Only way you can truely test it is unplug all the lights and plug one in that's not touching the body.

[PMCS Rally]

No lamps were plugged except one totally separated from the body.
I suspected the light switch failure so I disconnected 4-pin light switch connector and the light still turns ON....I tried with both Hella and Cibie and the result was same.

[510rob]

Disconnect all four headlight connectors, then jab a voltmeter probe into the headlight socket pins with 'red + no stripe' (right side) and 'red + blue stripe' (left side) and see what you get there as you switch the headlight switch on and off. The voltage there should be controlled by the headlight switch.

Check that out and report back to us.

[PMCS Rally]

Tested the Low Beam.
Both Right and Left pins of socket shows 12.5V at all three position (OFF-1st-2nd) of the light switch.
Center pin shows Ground Continuity at OFF position and no connection (open circuit) at 1st and 2nd position.

[CP]

Are the lights fully on or dimmed. If they are dimmed then I think you have some sort of a ground issue with current bleeding back through the common wire. I had a similar problem and ended up putting a diode in the common side of the headlight. That took care of it.

[PMCS Rally]

It look fully ON. Same level of brightness at all three positions (OFF - 1st position - 2nd position).
Hi/Lo switching on Low Beam works at 1st and 2nd positions.

Yes, I am suspecting some kind of grounding failure.

[510rob]

The +12V power to run the hi/lo relay comes from the running lights circuit, which is why the hi/lo switching works in the two outer positions (that is correct operation). The ground for that relay is switched through the steering column hi/lo switch, causing either the hi beam filaments to connect to power ground or the lo beam filaments to connect to power ground.

But for there to be 12V at the sockets when the switch is off? That suggests that something about your switch or wiring ahead of the headlight connectors isn't right. Go over that wiring as your next step. As crazy as it might seem right now, there should only be +12V at the headlights when the headlight switch is in the outermost position.