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Discussion Starter #1
1993 900 turbo convertible:

When I turn the headlight switch from position 1 "Off" , through position 2 "parking lights" ( works AOK) , then to position 3 "On" , headlights do not turn on.

I experimented with pulling back on the high beam / low beam dip switch stalk lever while the headlight switch was "on".
Result:
high beams would turn on and stay on if I also kept holding the stalk towards the steering wheel.
Low beams behaved the same way.

I am trying to isolate the cause of my non-working headlights.
I suspect the rotary headlight switch.

Can anyone confirm/refute this suspicion.

I would like to remove the rotary dial headlight switch to explore what might be visible.
A post in this forum suggested to turn the dial while jiggling it out.
I tried to turn the rotary dial in both directions/jiggle it out.
Failed.
Any guidance to remove the headlight switch?
What is the proper way to remove the headlight switch?
 

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Discussion Starter #5
Bentley manual section 3.2 electrical , page 106/320 shows the electrical schematic of the headlights, headlight relay, fuses 13&14 high beam,fuses 15&16 low beam, dip switch stalk lever.

Fuses 14,15,16,17 seem OK.

I am trying to understand the headlight relay theory/testing procedure.
I never saw a relay this complex.
I am familiar with routine control switch solenoid circuit terminals 85-86 and the slave/load circuit terminals 87-30.

How do I bypass the headlight relay for testing?
I am guessing that by turning the headlight rotary switch to the far right "on" position, the relay should make an audible click and power supply should flow to both headlights.

I will attempt to attach a schematic of the headlight relay component #8 in the Bentley electrical diagram.

My speculation is that:
- headlight relay 12v control supply enters master control solenoid circuit at terminal 86 from headlight rotary dial and gets grounded to chassis through terminal 31.
- slave /load circuit gets constant 12v from terminal 30 and gets grounded when master control solenoid circuit is energized . Grounding is through either hi beam circuit 56A fuses 14 and 15 or through low beam circuit 56B fuses 16 and 17.
-the switch stalk will flip the slave circuit to either terminal 56A or to terminal 56B.
 

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Please remember the headlights are also energised from the ignition circuit. When you turn ignition off the lights go off. This is activated from the headlight relay. Another level of complexity you may have overlooked.
 

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Headlight switch has 2 different power supplies: +54 voltage and +X voltage.
+54 voltage powers headlights when switch is in LEFT (if DRL fuse is present).
+X voltage from ignition switch pin X.

Check if you are missing voltage at headlight switch pin +X.
 

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Discussion Starter #8
New data:
When I rotate the headlight switch to the ON position, and then slightly tweak the headlight switch ( as if to get better contact in the switch ) , the result is : Success. I can get both high beam and low beam.
I feel that the issue has been isolated to the headlight switch.

I need to remove the headlight switch to explore what is happening in the switch contacts and possibly replace the headlight switch.
Question:
How do I remove the headlight switch ?
 

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Discussion Starter #10
success.
jiggled the switch out by keeping the switch pointed to noon and pull/jiggle/pull.

Once the switch was out, I could see that the rear half of the switch was pulled away from the main body because the keeper latch was snapped off and the large spring was forcing the two halves apart.

I sanded both plastic body halves to give the smooth plastic some teeth/ rough surface.

Then, I bound both halves tightly compressed together with duct tape.
All lights working.
Thank you all for chiming in with guidance as I did not know what my issues which caused no headlights.
 
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