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

Rad Face

Our fan slid out with ease after about 5 to 10 minutes from opening the hood to expose the back side of the radiator which is in great condition.  The center bolt on top and bottom will need to be removed for fitting the new fan.

style=”line-height: 20.8px;”>Closeup RadThe stock copper brass radiator is a single-pass dual-core design with provisions for a third core.  The end tanks are wide enough to support a third 1-inch core and since the Viper is a “parts-bin special” it’s possible the radiator was taken from a different vehicle and only two cores were needed.

Some Viper owners have a third core added by a local shop or re-core the entire radiator. The execution and build can vary drastically from shop to shop and without proper testing; the change in capacity vs flow vs heat transfer of a third row is unknown. Keep in mind that thicker isn’t always better and while bare brass has a higher thermal conductivity than aluminum, the brazing process and black painted coating greatly reduce the efficiency of the radiator.

Aluminum radiators typically weight 1/3 of a copper brass radiator and can be made with much wider tubes (>1.5”) with dimples to increase the surface area over a standard 7/8” or 1” smooth copper brass tube.  There are a lot of reputable companies out there (PWR, C&R, Ron Davis) who are heavily involved in motorsports and offer far superior products.

Stock Fan on Ground

The original 1996-1997 radiator shroud has a 15.5-inch Outer Diameter fan offset with (4) plastic flaps that open at speed to improve airflow.

Stock Fan Angle

The fan is oddly angled to the driver’s side while the flaps are straight.

Stock Fan Flaps

These plastic flaps have 67.08 square inches of surface area to allow more airflow at speed.  The whole shroud, fan, and flaps become a restriction at speeds above ~45mph so these flaps are crucial to improve the efficiency and performance of the radiator. If the car never goes below 45mph, not having a fan or shroud would be the best for cooling flow and efficiency, but in traffic, the fan and shroud is crucial and the only way the radiator gets airflow.


  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!

  4. good evening i have a 1999 viper GTS and i just got the radietor from you do u by any chance sale the hole kit for the fan to make it work better please let me know so i can buy ti thanks

    1. What temp does the fan kick on? Did you change the low or high speed fan temp threshold by flashing your ECU? If you’re tripping the 60A circuit breaker, then you need to troubleshoot and find what is causing the excessive amp draw.

  5. Is the Bosch relay with the 332 209 151 number the same relay? Stats look similar to the one you have installed

    1. Those appear to be 30A relays vs the 50A relay that I used. I would recommend using the part number for the 50A relay.

  6. can u send me more detail about the wires evething look nice but i can not see every cable where they go to make shure i conected right i need the order or a better pictures can u send me a diagram i got all the parts thanks

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