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

Deutch connector

We ran the male connector to an easy to access location that would be out of the way and in easy reach of our fan wire.


With the power line ran, we cut the fan-side wires to length, crimped, soldered, and shrunk the female Deutch connecter to it and plugged it in to complete the connection.

stock relays

The OEM 30 Amp relays (Part # 56006709) are located in the Power Distribution Center (PDC) next to the ECU.  While the stockers should be fine for our new wiring, why take the risk?

40 Amp relays

If you install (or have) the 98+ fan and don’t run a standalone power harness and relays, upgrading the relays are a must. We used these 40A TE Relays (Part # TYR-037-1240 from Terminal Supply Co) that are rated to 100*C to replace the OEM 30A relay.

40 amp relays installed

Once plugged in, the install is complete.

Finished Install

Unfortunately, all of our hard work won’t be visible once the airbox is installed, since it looks and performs so much better than the original that we removed.

Once fired up, we were pleased that our wiring was correct and everything worked perfectly.  Due to the new 1998-2002 fan’s curved blades, fan operation is noticeably quieter with a lower-pitch ‘whirl’ to it than the original, which sounded like it was spinning faster with a loud audible ‘whine’.  With the high speed fan on, the suction from the front grille opening is impressive.  It will suck a paper towel in from over a foot away!

Project Viper GTS lives in South Florida where summer months are in the mid to high 90’s and humidity is often over 80%, so cooling is very important. With our aftermarket temperature gauge mounted (in Part 2), we frequently saw temperatures of 217-220*F when stopped for long periods of time, which would trigger the high speed fan to kick on (at 216*F) which would either slowly bring the temperatures back down, or stabilize until the car started moving again; where it would cool down to 190-205*F once moving.

Keep in mind the stock 195*F thermostat bypasses the radiator entirely until 195*F where it starts to open and allow coolant to go through the radiator.  Coolant continues to bypass the radiator and inject hot water back into the engine at varying amounts until the thermostat is completely open at 219*F where it closes off the bypass allowing 100% of the coolant to flow through the radiator.

With the new fan installed under identical conditions, the low speed fan’s 2,020 CFM was able to keep the temperatures under control.  We rarely saw over 210*F when stopped for long periods of time, which was 6*F shy of kicking on the highspeed fan for 17% more cooling (2,370 CFM).  Without knowing for sure and after extensive research, I suspect the original fan’s highspeed setting was in the neighborhood of 2,000 CFM and the lowspeed a good few hundred less than that.

Overall we are extremely pleased with the results of the new 1998-2002 fan and wiring.  Not only did we greatly increase the cooling of our car both when stopped and moving, we now have the confidence that our fan can run constantly without the risk of melting down our wiring, relays, and $500 PDC.  With that comfort, we will try lowering the temperatures for both the LS and HS fans to see how that performs in a future article.  Stay tuned!






  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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