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Discussion Starter · #1 ·
Hi All,

2009 Mazda 3 BL

I've noticed when idling for long periods of time the radiator fan never comes on. Since this model year Mazda got rid of the temp gauge I used a generic OBD scanner to check the temp and it seems to climb very high, to 110c . When driving the air movement brings it down so the thermostat is opening.

Strangely though when the AC is on the fan does work. As a precaution I drive with the AC on all the time now.

What could possibly cause this and how do I go about diagnosing and solving this ?
 

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Hi All,

2009 Mazda 3 BL

I've noticed when idling for long periods of time the radiator fan never comes on. Since this model year Mazda got rid of the temp gauge I used a generic OBD scanner to check the temp and it seems to climb very high, to 110c . When driving the air movement brings it down so the thermostat is opening.

Strangely though when the AC is on the fan does work. As a precaution I drive with the AC on all the time now.

What could possibly cause this and how do I go about diagnosing and solving this ?
2009 is BK is USA. 2010-2013 is BL. If a BL tho your fan module has stopped working. One closer to the air filter box. This is common. I am a Mazda master in Orlando, FL. Can check 2 ways really. Tap in module. This is bolt straight to fan where motor is for fan see if comes on or twitches. Or check for power and ground at the bigger of the 2 connectors going to fan. Obviously when fan should be coming on at the correct temp. If you have 12 volts on big red wire and a good ground you have a bad module. Replace. This is 99% of what happens. Similar year 6's had same issue. Have to replace whole fan assembly on 6.
 

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Discussion Starter · #5 ·
Thanks guys. I have ordered OBDlink thing so I can test the module out first. If it confirms its bad I'll order a new one. I guess I should not take chance on a used one and better go for a new one eh
 

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Never seen a dtc for this issue. Just a power problem dont yhink its going to tell u module failed. Still communicates with this issue. Just tap it or un plug it and replug. If comes on when unplugging and replug it in its def. A fan module.
 

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Sometimes, depending on what the module actually is, you can remove cover and clean the contacts or resolder cracked solder joints if its the module. I never had an issue with it on 3 mazdas, but have messed with on other cars.
 

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Discussion Starter · #8 ·
Never seen a dtc for this issue. Just a power problem dont yhink its going to tell u module failed. Still communicates with this issue. Just tap it or un plug it and replug. If comes on when unplugging and replug it in its def. A fan module.
Yep no DTC for this issue but one can test the fan duty I believe. If nothing happens when I try to test it from the software than that confirms bad module no ?

If I unplug the module, there'd be no power to the fan at all so can it run at all ? I see input the module and output to the fan.
 

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It's great to have the ability to scan with a reader and I have a cheapo set up for the Mazda and a much better set up for VW/Audi.

In this instance a Mazda tech has told us, well you, all you need to know. These guys see this every day, we see it every now and then.

I do what Jeremy suggest before I did anything else. Need to know fan will come on when needed unless you want to blow head gasket or worse.
 

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Just unplug for a few seconds and replug. Sometimes fan will kick on. Obviously has to be temp to want to run it. 205 215 somewhere in there. If does not kick on like should unplug replug. If comes on u def have a bad module. Ur making it too complicated checking software. Not needed for this. On a 6 this was the check at mazda. Unplug it plug it in see if kicks on.
 

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Discussion Starter · #11 ·
I tried the unplug and replug. Fan didnt come up. It was upto temp and getting hot. As before only comes on when I turned on the AC.

I bought the obdlink thing anyway. I want to work on my own car so its kind of an investment and anyway cheaper than me paying someone to diagnose it.

I ran some tests for fan and on command I can set the fan duty cycle and it comes on. So i doubt that the module is bad.
It seems as if the setpoint is wrong.

Is there anyway this can be changed ?
 

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well, I've never taken one apart so can't say if it can be adjusted. From above you know the fan works, right? There is only 1 fan, not a dual fan setup. So, if fan works, but doesn't come on when coolant hits temperature then the sender that tells the fan to turn on is either dead or wonky. I'd just replace the sender at this point, but thats me. I hope it works out for you.
 

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Discussion Starter · #13 ·
well, I've never taken one apart so can't say if it can be adjusted. From above you know the fan works, right? There is only 1 fan, not a dual fan setup. So, if fan works, but doesn't come on when coolant hits temperature then the sender that tells the fan to turn on is either dead or wonky. I'd just replace the sender at this point, but thats me. I hope it works out for you.
Where can I find this sender ? I am wondering, would this sender be responsible for giving the temperature read out that I see in the diagnostic ? In other words, if I can get a temp reading I should assume the sensor is fine.
 

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Discussion Starter · #15 ·
so I tried something yesterday. I disconnected the temp sensor. Check engine light, temp lights all came on but the fan went full speed. Temp reading according to OBD is 0. So somehow I dont think its the sensor. Any thoughts ?
 

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Discussion Starter · #18 ·
Did you ever get a resolve to this as I have the same issue too
Hey mate i did some more investigation. So far on my Mates car I see that the fan comes on at 100c albeit very slowly just to bring the temperature down to about 97c, and the process repeats. So looks like the trigger temperature is 100c.
I am going to reconfirm with my car and let know here.
 
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