Radiator fan always on at high speed?

[frankybody]

Hi, my 2017 CX-9 Signature radiator fan runs at high speed all the time and the temperature seems ok on the dash. Does anyone have any advice on what could be causing this..? Thanks in advance!

 

[Mazdiod2]

Here's a recent thread about the Engine control sensor. Since your dash reads an ok temperature maybe in your case you have an issue with the actual switch or circuit that controls the fan, which is shorted or in the closed postion.

2016~2023 Thread 'CX-9 Engine coolant temperature sensor'

Aug 9, 2025

Hey guys, hoping to get some help from the community on this one. I can't seem to find the location of the coolant temperature sensor on the engine. Everything I could find on the Internet shows the location of the sensor on the previous gen, or the location of the sensor on a 2.5 non-turbo. Usually it's easily visible by the thermostat housing, but I can't seem to locate it on the 2.5T. To be fair, I haven't taken the battery out or anything, but I wanted to get an idea of where it is before I start ripping stuff out. Any ideas?

The part number of the sensor is SH01-18-840 if that helps.

• sm1ke
• Replies: 12
• Forum: CX-9 Powertrain

The test points for the cooling fan relay are found here (CX5) CX9 hopefully will be very similar.

Mazda CX-5 Service & Repair Manual - Cooling Fan Relay - Cooling

www.mcx5.org

 

[sm1ke]

Here's a link to the CX-9 workshop manual if the helpful information posted by @Mazdiod2 isn't enough.

L

Post in thread '2016 and up CX-5 Service Manual'

Mar 1, 2024

here is for everyone
Mazda 2

M A Z D A

Mazda2 (dj/DL)

M A Z D A

Mazda3/Mazda3 MPS (BK)

M A Z D A

Mazda3 (BL)

M A Z D A

mazda3 (BM)

M A Z D A

Mazda3 (BM/BN)

M A Z D A

Mazda3 (BP)...

• luklyz

• 
• 

Click on the link for the CX-9 (TC), which is the 2016+ generation.

 

[frankybody]

Thank for the reply