Jimmy,
Your best bet is to run a relay from the A/C clutch power. Run your 30A fused power to the relay and the normally open contact of the relay to the fan motor.
The A/C thermostat would cause the clutch to operate when cooling is needed, this then operates the relay and provides power to the fan, without needing to draw the ~10A thru the ACC control wiring or controller.
Tony

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.