We have a 2005 Madza 3. Our daughters car. Started over heating last week. We noticed the fan doesn't kick on.

We have replaced the thermostat, ECTsensor. Auto parts store allowed us to test a new fan & control module unit yesterday and it didn't come on.

What test/procedure would a Madza mechanic do next to test to see what is wrong?

Look forward to hearing your suggestions.

Kevin

 

Check the connection to the fan itself, if you can try to put 12V directly to the fan and see if it turns on, if yes then check further "upstream", you may have a bad fan relay or even just a bad ground ("downstream"). I will BRB after I look at my 3 and see what it looks like.

 

Ok took some pics of mine: The Fan & CU pic is of my fan and CU, this is what I am guessing they replaced as well correct? The pic titled Fan Power Connector is where you can unhook the connector and check for 12V coming from the car to the fan, turn the AC on to force the fan on (it will cycle so there may be 12V then 0V then 12V etc). Next open your Fuse Box, as shown in pic Fuse Box Cover Off you need to also remove the small black cover that I highlighted in red. Under this cover (Picture: Fuse Box Fan Cover Off) you will find the fans fuse, it is a 40A connection and I also highlighted it in red. Check voltages here as well and a continuity check of this fuse (unhook connections first before continuity test).

 

I have done the work myself, so far and I am at a stand still on what to do next. I checked the 40 amp fuse, good. I checked voltage and ground at the connector on the fuse box side of the connector, good. And my multimeter also has a Freq. duty cycle test and I was getting a reading from the PCM. I could hot wire the fan and get it to run at the fan connector. I have replaced the ECT. I have also tested a new fan assembly that included a new fan control module. And still the fan does not come on when the A/C is turned on or when the temperature guage is almost at the H.

 

Behind the left headlight is a ground wire for the fan control unit, I think you have to remove the headlights (do left side first for I think that is where the fan is grounded) and check the ground there. Since you said you were getting a PCM signal were you also getting 12V at the fan connection?

 

Yes, I am getting a 12.5V reading at connector on the fuse box side of connector. I will check the ground behind the headlight. Thanks for the information.