To repeat my reply above, you've almost got it, just one misundertanding to overcome. 30 needs to be ground. If you check your instrument cluster wiring diagrams carefully, you'll see the dash light is seeking ground, not wanting power. That's also how they can have all the lights illuminate in KP-II when the alternator isn't running.

Edit: Best not to run 12V up to the sensor and back to the relay for ground (that's not how the 960s are wired), do it my way, plus you've got it backwards for some relays that have a diode on the coil. Do you have that open reservoir connector present under the hood? If present, you can do everything up under the dash behind the cluster using my suggestions.

(sorry, multiple edits going on here while thinking and typing on a tiny keypoad)
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now