Cylinder Relais question?

sfdon

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I believe the high beam filaments act as the ground at pin 85 on the fog light relay.
Once the high beams are turned on and the lows are off the ground becomes a positive at that pin which gives the relay a positive at pin 85 and no longer a positive at pin 86 deactivating the relay.
Note pin 85 is the connector with 3 white wires, 2 that go directly to the high beams and one from the high/low beam switch. Also note that the right high beam wire in the schematic has a labeling error or errata with its reversal of the description of wire color from “ws “ to “sw “.
The positive at pin 86 comes from the fog light switch directly from the low beam circuit.

So- low beams power the fog light switch which activates the fog light relay.
With low beams off- no fog lights.
With high beams on- no fog lights
Only with low beams on and fog light switch on do you get fog lights.
And if you wire low beams to stay on with high beams you still get no fog lights.

The “toggle” is fog lights go off when low beams go off or high beams go on.
 
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sfdon

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Btw- the only reason for a ground at the fog light switch is to illuminate the switch.

And finally! - all this is based on the 73/74 euro schematic with city lights.

Item 15 is the fog light relay...
 

Willem Tell

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Thanks for filling in the blanks Don. I didn't think about the light filament as a ground path for the "toggle" action.
I don't intend to mount fog lamps, so I could:
modify the wiring on the forward Fog Light relay base to use the single white wire from the high/low beam switch at Pin 86 and add a ground to Pin 85 to operate the relay coil to switch the High Beams,
add an in-line fuse on the battery power to Pin 30,
Move Black and White wires from Pin 85 to Pin 87 [disconnect yellow (GE) fog lamp wires at 87]
This would still look totally stock, and could easily be reversed if I decide to add fog lamps.

Sound right to you?

Alternatively, it's easy to add an additional plug 'n play harness (as I did on The FunMobile):
Works well, but then you've got two additional relays and another harness in the nose...
My version of the '02 circuit:
Headlight Relay Circuit PPT Tom.jpg

upload_2019-1-17_17-9-37.png

upload_2019-1-17_17-11-5.png
 
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