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

Stock fan flap gap

The stock fan flaps have angled cuts on the outer corners of the flap and a rectangular notch on the opposite side. While we don’t know the reason for this, it greatly reduces the efficiency of the fan when the car is stopped.  As the fan creates a low pressure area behind the radiator; ambient air from the engine bay enters through these gaps (including the flap mounting tab holes) which reduces the fan’s ability to pull air through the radiator to cool it down.

New fan flaps

The new 1998-2002 radiator fan (Part # P5007266) has a much larger 17.5-inch OD fan that’s centered between four rubber flaps with 60.32 sq. in of surface area. The 40 Amp fan is rated an impressive 2,020 CFM at Low Speed and 2,370 CFM on High Speed according to and, which rivals some of the best aftermarket fans out there.

>New fan flaps underside

The 8-blade fan has forward-facing curved blades which typically sacrifices a small amount of performance for much quieter operation over an equivalent straight bladed fan.  Compared to the original 7-blade fan, the new fan should have a quieter operation and greater flow thanks to the additional blade which helps to create a higher pressure drop at the face of the radiator.

New fan flaps

Instead of plastic, the new radiator has these rubber flaps which open much easier and create an improved seal when closed under vacuum to pull the air through the radiator better.

While the 98+ fan is a plug-and-play for our 1997 GTS, there have been multiple reports in the Viper community of melted relay boxes in 98+ cars as well as early Gen 2’s with the 98+ fan installed.  Since the factory relays and more importantly, the wiring, is suspected to be too small for the increased draw from the larger fan, we decided it was not worth the risk of damaging our $500 PDC (Power Distribution Center).

Melt Relay

The factory 30 Amp relays and 14-12 gauge wiring does not seem to be large enough for the increased draw of the 40 Amp 98+ fan.  The buildup of heat can melt the factory PDC relay box.

To address this potential problem, we decided to run our own dedicated power and ground wires and use the factory relays and wires as a trigger to our standalone relays which will carry the load of the fan.

WARNING: Because the 98+ fan is rated at 40 Amps, when installing it in an earlier car it’s crucial to replace the factory 30 Amp relays with 40 Amp relays.


  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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