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

Project Viper Part 5 Rad Fan Cover

The Viper is a “racecar for the street” in more ways than one; and like a racecar, it does not like to sit in stop and go traffic and can run hot and overheat without proper airflow on a hot summer day. To combat this we upgraded the radiator fan on our 1997 Viper GTS with the higher flowing, larger fan from the 1998-2002 cars. In addition, we safeguarded the potentially flawed wiring and relay box by running standalone relays with dedicated power and ground wires.  To further extend the life of the relays we used a trick pair of “NOsparc®” spark supressors in the harness.

It is apparent the factory Gen 1 and Gen 2 radiator fan was not up to the task of cooling the Viper’s V10 engine on a hot summer day due to the redesign and increase in diameter 1998.  We turned to the Viper experts at ROE RACING to upgrade the fan in our 1997 GTS with the more powerful 1998-2002 fan.  We also picked up a 60 Amp circuit breaker, 50 Amp relays and NOsparc® Arc Suppressors to prevent melting the factory relay box.

Viper Radiator Fan NoSparc Circuit breakers

The 1998-2002 OEM fan is a direct fit for 1992-2002 Gen 1 & 2 Vipers.  While the electrical connection is plug and play for 1996-1997 cars, 1992-93 RT/10s require modifying the wire in the high and low speed settings for the fan and 1994-95 cars require reusing the original fan plug. Sitting next to the fan are the NOsparc arc suppressors, 60 Amp circuit breaker, 50 Amp TE relays and relay harnesses that we are going to mount to the fan for a standalone wiring harness.

It’s not hard to believe that Vipers run hot since they have one of the largest engines ever fitted in a production sportscar.  Despite a very small grille opening, they typically don’t have a cooling problem when on track where speeds are rarely below 45mph.  On the other hand, stop and go traffic can be a killer since it’s solely up to the radiator fan and shroud to provide enough airflow through the radiator to cool the car’s engine while stopped.

Front Grill

With only 119 square inches of front grille opening in Gen 1 & 2 Vipers to feed the oil cooler, A/C condenser, a 400 sq. in radiator, and power steering cooler; there is a relatively small inlet to cool the large 8.0L V10 engine. By contrast, Project E90 M3 has 220 sq. in of inlet area to cool an engine half the size of the Viper.

Stock Viper Fan Pre 1999 Mounted

After removing the airbox, we have access to the radiator fan and unplug it from the car harness.

Fan Bolts

The original fan is held on by six 10mm bolts which are easily removed.


  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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