Much thanks to lucid; he often has the pinout and wire colors for us.

The yellow and white wires at the relay will have power only when that relay is plugged in and headlights are switched on with ignition in an appropriate position.

If all seems well at the relay you can test that same yellow wire up front where it meets the high/low "step" relay. With headlights switched on it should have 12V.

That front relay routes the voltage EITHER to the high beams via red wire, OR to the low beams via blue wire, first to the bulb failure sensor and from there to the low beams. The high beam circuit routes directly to the bulbs skipping the failure sensor.

Good luck!
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Sven: '89 245 NA, 951 ECU, expanded air dam to 7' from ground, forward belly pan reaches oem belly pan, open-front airbox, E-fan, 205/65-15's at 44 psi, IPD sways, E-Codes, amber front corner reflectors, quad horns, tach, small clock. Wifemobile '89 245