There’s two 350Z cooling fans in your Nissan roadster, both primarily set to pull or draw air through your radiator. One happens to be a primary radiator fan that’s activated by your Nissan ECU, and the other is activated through your air conditioning. If your 350Z starts running hot, you want to do your best to stop your Nissan from overheating.
The first one of these steps is to check your engine coolant temperature sensor. This can be done using our handy guide here because this is what triggers your cooling fans to turn on. The most obvious sign of trouble other than your rising 350Z engine temperature gauge is the lack of cooling fan noise in your engine bay.
Left uncorrected or untested the lack of your cooling fans in your 3.5 liter VQ35DE engine can cause your 350Z to overheat. Over 220º Fahrenheit your cylinder heads will begin to warp and distort. This will cause your head gaskets to blow out, and you’ll lose cylinder compression as your engine begins to mix oil and coolant.
Today I’ll be showing you how to test your 350Z cooling fans in a 2004 Nissan Roadster with the 3.5 liter VQ35 in it.
Our test vehicle has already tested the engine coolant temperature sensor, using our How To Guide.
Now it’s time to test the radiator fans, which will require you to use a digital multimeter. If you aren’t sure what that is or how to use one check the DIY tutorial here on voltmeters and multimeters. Because you are working around your cooling fans, make sure to always leave your key turned OFF while disconnecting your radiator fan connectors. To begin start your engine and allow it to warm up completely. If your 350Z is overheating stop when the temperature needle reaches the midway point, or your idle changes from your ECU changing to the warm fuel map.
Open your hood with the ignition turned OFF and locate your cooling fans connectors. Depress the locking tab and pull apart to disconnect the harness.
Once you have the 350Z radiator fans unplugged, you can begin testing. Make sure to disconnect BOTH because you don’t want them turning on for whatever reason. Now turn your Nissan ignition to the “ON” position and you’ll be testing for power first.
Testing your 350Z Cooling Fans for Power
Put the black lead of your multimeter to the negative battery terminal, and then gently probe PIN A first for a power signal. Then check PIN B in the 350Z Cooling Fans wiring diagram as shown below.
You have two speeds that operate through your Nissan radiator fans. At LOW speeds, the power wire is the one labeled B and the ground is PIN D.
At HIGH speeds the power wires are both PIN A and PIN B. The next part is to check for a ground signal, which will involve you switching your multimeter leads around.
Put the RED multimeter lead to your positive battery terminal and carefully probe PIN D with the BLACK lead. If you have ground here check for ground at PIN C as well. Have both power and ground at these pairs of wires? Looks like your 350Z cooling fans have burned out and you’ll need a replacement.
Remove the 10mm bolts that hold the 350Z Cooling fans and the fan shroud to the radiator. Remove the 350Z Cooling fans and install your replacement radiator fans, and you should not need to remove the radiator for this job, but you’ll have to disconnect the upper radiator hose to your 350Z.
Have any questions about your 350Z cooling fans or this tutorial? Want to learn more about your Nissan 350Z? Leave us a comment below and don’t forget to subscribe to My Pro Street to get all the latest tech tips and automotive news.