I cant get my passenger side fan to turn on unless the motor is off, the ignition is on, and i turn on the AC. Thats the only way it will come on. I was wondering if I can just splice my secondary fan power wire into the wire for the primary fan and then they will just both come on at the same time. Do i splice into the secondary + wire into the negitive of the primary or the + into the + or the negitive into the negitive or what? Thanks for the help, i need to get the car running right today so I can make it back to michigan without overheating.

 

Ordinarally the AUX fan won't come on until the temp hit's about 235 degrees. Your primary fan should trigger around 222 or so. Also the AC head pressure switch controls AUX fan operation in conjunction with a temp sender on the passenger side head. Sounds like it is working properly. As the car idles when the guage is a little past the 220 mark primary fan should start(driver side fan), the as it climbes the secondary will come on. Ambient temp and AC compressor request will dictate whether the AUX will come on. In a normal TG on highway driving with an intact airdam neither fan usually never runs. They generally activate with city stop and go type driving. As far as turning on both fans I really don't feel it is wise. Unless you suffer from chronic overheating usually the result of another cooling problem all you do is place undue load on the alternator. If you are still so inclined you need to control the fan relay coils. These are the two smaller wire at the fan relays. One side of the coil goes to 12 volts the other side is controlled by the ECM and fan switch. You will need a voltmeter to see which side of the relay goes low when the fans turn on, then use a switch to ground these wires. The ECM internal driver may not be hefty enough to drive two relays, would't risk it. Also one fan relay WILL cook if you try to run two fans. it is possible to have a defective secondary fan switch but it is rare.