Project Viper GTS: Part 5 – Radiator Fan & Wiring Upgrade

Fan wired

Having connected MIL-spec wire to all six wires (three on the fan and three on the plug) we shrunk everything in 3/8” Raychem shrink wrap and used adhesive shrink to seal off the ends.  We ran both sets of wires to the passenger side where our relays are mounted and zip tied the wires neatly out of the way.

Despite using standard (cheap) automotive-grade wire with relatively weak insulation, the 99+ fan has a decent gauge wire given its 40 Amp draw:

Chassis Side Wire ColorFan Side Wire ColorDescriptionGauge Wire
BlackBlackGround12 awg
Dark Green (middle)Brown/Red (middle)Low Speed Fan14 awg
Light GreenBrownHigh Speed Fan12 awg

NOsparc Wired

The NOsparc® arc suppressors are wired as drawn in the diagram earlier.  The Red wire connects to the hot side which always has power while the Black wire becomes hot once the relay triggers it to switch on.  This is when the Arc Suppressor does its job to eliminate arcing to prolong the life of the relay.

NOsparc Gap

The NOsparc suppressors are also mounted with a ¼” gap for better insulation.

Relay Wiring

Wiring the power, ground, triggers, and NOsparc was a bit time consuming given that each wire was crimped, soldered, and shrunk.  This was as elegant as we could make it.

Finished Wiring

Now the wiring is finished.  The main power and ground from the circuit breaker travels along the bottom of the radiator shroud and up to the relays before following the new wires to the center of the fan motor. The factory plug’s ground and low/high fan wires travel to the relays across the radiator face and act as triggers to send the power to the fan motor via 10 gauge MIL-spec wire.


  1. Radiator fan wiring upgrade they auxiliary relays what wires output to the fan either number or color it’s not clear thank you for your help

  2. Have a customer with a 96 wanting to do this upgrade to his cooling system, any idea where the cooling fan may be available?

  3. That’s weird. I’ve always been taught to crimp ring terminals on the cut side, so it forms a B-type crimp that secures the wire. Well, whatever works!

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