Parallel Fan Operation - '99-2000

by Manuel De Brito

I wanted maximum cooling under the following conditions:

A/C ON - Both fans on to help reduce heat produced in the engine compartment by allowing improved air flow through the engine compartment at idle.

A/C OFF - Both fans on when the temperature is above normal. Only one fan used to turn on in my car when the A/C was off and the temperature above normal.

I always wondered why both fans in front of the radiator didn't come on at the same time. One is for overheating for the cooling system and one is extra for when the A/C is turned on. Wouldn't it be better if both came on at the same time to cool off the engine quicker especially in hot weather where the A/C compressor will add to the heat and stress under the hood?

Well, I looked through the schematics and came up with a solution in my '99 and probably will work for the '00 too. I am shooting for maximum cooling under the following conditions:

A/C ON - Both fans to help in cooling and reduce heat produced in the engine compartment. Both fans on will flow air through the engine compartment better at idle.

A/C OFF and OVERHEATING ENGINE - I want both fans on when the temperature is above normal. Only one fan turns on in my car when the A/C is off and the temperature is above normal.

  1. You need one 8" 14 gauge wire and two wire taps or as suggested, solder.
  2. Open the hood. Pretty easy so far.
  3. On the driver's side of the engine behind the headlight there are three relays covered in black rubber. Unbolt the middle one. There is a light green wire with a black stripe. Tap one side of your 14 gauge wire and wrap the wire in electrical tape or your favorite method. Reinstall the relay.
  4. Then look at the driver's side radiator fan. There are two sheathed wires (yellow and black) leading to the hub of the fan and connect in. Follow the wire back to the body of the car and tap into the YELLOW wire. Tape up the connections or use shrink tubing.

It's a 15 minute job taking your time. When one fan turns on, the other will also. This will cool down the engine much faster with the two fans on. For those in hot weather, I hope this helps.

Thanks to Hakuna for doing this on his M1 and giving me the idea for my 99.

Manuel De Brito

Precautionary note from Jeff Anderson (7/30/02):

In this rewiring method the electrical contacts within the Cooling Fan Relay carry and switch the high current inductive electrical loads of two fans while designed to carry the electrical load of only one. Although the relay's reserve design capacity is unknown, it's likely not double as would be required for dependable operation of this critical relay over time. A Cooling Fan Relay failure can result in overheating and total destruction of the car's engine.

Please see the thread on our forum archives.

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22 June, 2008