Lights on & off with engine running?

[kd69bug]

Curious if anyone has rewired so that when the engine is running, headlights and taillights are on, and shut off when car is turned off. Seems like it should be fairly easy, but...?

[runamoc]

already done....search the forums about the X wire and associated circuits
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Daily driver: '69 Baja owned 44 yrs - Plan B: '81 Rabbit Diesel LS Deluxe - Plan C: '72 Ghia
Yard Art: 2 Sandrails
Outback: '69 Ghia - '68,'69,'70,'72 Beetle - '84 Scirocco, GTI - Pair of '02 Golfs-
VW Wiring = It's just wires

[ashman40]

runamoc is correct. VW added the "X" circuit to the ignition switch in the '71 model year. Same year the first SB came out.

The X circuit is the black/yellow wire coming out of the ignition switch electrical unit. In '71 it went directly to the newer style headlight switch. From '71-onward the headlight switch had two completely separate subsystems. The parking lights and illumination lights were powered from the #30 red constant 12v wire. This allowed the parking lights to work even when the ignition switch was OFF. The headlights were a completely separate circuit thru the headlight switch. It was powered by the "X" terminal and output from the switch went to the headlight dimmer relay which selected whether the hi or low beams were powered.

The X circuit is ONLY powered when the ignition key is in the ON/RUN position. So when the key is turned OFF the headlights are powered down even when the headlight switch is fully ON (parking lights will remain ON since they are not powered by the X circuit).

Unlike the black #15 ignition switched circuit the X circuit is NOT powered when the key is in the START position. This is the primary reason for the X circuit... to conserve current draw from the battery while starting the engine. When the starter is engaged and drawing huge current load from the battery, anything powered by the X circuit (non-critical subsystems that do not need to be powered when cranking the engine) are shut OFF, thus freeing up additional current for the starter and ignition coil.

From '72-onward the X circuit coming out of the ignition switch was wired directly to the #10 fuse in the fuse box. In these later years the #10 fuse was a standalone fuse for non-critical systems. Wipers and blower fan were powered by fuse #10. The headlights were still powered by the X circuit but instead of being directly powered by the ignition switch the headlights were connected to the INPUT side of the #10 fuse, so the headlight switch was powered by the fuse box but not protected by the #10 fuse.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[kd69bug]

Great info! Thank you.