Mazda3 Forums banner
1 - 9 of 9 Posts

· Registered
Joined
·
147 Posts
Discussion Starter · #1 ·
Hello everyone,

My radiator fan doesn't turn on even when my car starts to overheat. I have a scanguage and my coolant temp will reach well over 220F when sitting at idle for a long time and the radiator fan will not come on. Turning the AC on does turn the fan on though.

I have already replaced the coolant temperature sensor at the back of the head, to no avail. What tells the radiator fan to kick on when the car is overheating? Is it the thermostat?

I have no check engine codes, and I have tried disconnecting the battery to reset the computer, but no luck so far.

Any ideas? Thank you.
 

· Registered
Joined
·
147 Posts
Discussion Starter · #2 · (Edited)
I just wanted to /bump/ this post because I have not found a solution to this problem yet. I have heard that there is a controller that is actually mounted on the fan/radiator that turns the fan on and off when it's supposed to. I am wondering if I should go ahead and order a new fan and radiator.

The water thermosensor is operating normally, My car reports 190 degrees most of the time until I start idling, it will climb well past 210 degrees and the fan will not turn on. It also does not turn on for a few seconds after I shut off the car like it used to. The fan still turns on when the AC is activated.
 

· Registered
Joined
·
31 Posts
It cant be the fan, and there is no switch. The fan is controlled via PWM through the fan control module. Before you say the module is bad, it also cant be (well in my case) I used forscan and the test works fine, all duty cycles the fan comes on.

It almost seems to me its a design flaw. The ECU doesnt tell the fan to come on at the right temperature. I am going to check with my mate who has the same car if he has the same issue. If so i'll make a video on it and post link here.
 

· Registered
Joined
·
15 Posts

· Registered
Joined
·
284 Posts
There are some already good thoughts on how-to-"repair" the problem. Another consideration...
I personally never liked how the ECU controlled the fans. For my late production 2018 Mazda 3 I have by-passed the ECU operation and installed an aftermarket fan control. I modified it to either control during AC on and defrost operation and also to activate if the water temperature exceeds 200F. I also have a by-pass switch that I can turn on the fans at any time. The last thing I did was to enter the ECU fan control PID and turn off all the fan setting. Not necessary just a thorough procedure on my part.

A simple universal fan control can be installed by any DIY in about 2 hours.
 

· Registered
Joined
·
15 Posts
its so weird with this model... not controlled by the ecu, but by a dumb fan control module right next to the fan motor itself.

the quick bypass/temp fix was to turn on the AC and manually run the radiator fan that way until they can source a replacement module
 
1 - 9 of 9 Posts
Top