My daughter has a 2010 Mazda Tribute with 180k KMs on it.

She was over the other day and both cooling fans were running when she got here. It was a cold day so this seemed odd. She says it always sounds that way and come to think of it, last summer when I tried to apply belt dressing, it went everywhere because the fan was blowing. I didn’t think much of it at the time as it was summer. The fan comes on shortly after the car is started and goes off after the ignition is shut off.

The coolant level is fine and the temp gauge is always where it is supposed to be when it is running. There are no warning lights on the dash.

I suspected a stuck relay. I tapped each on in place then removed them one by one. I did this by turning the car off, removing each one, then starting it back up. The fan did not stop after I removed any of them, which I found odd.

Next I unplugged the power to the drivers side fan and it the fan then shut off.

I have read it’s either the head temp sensor (but why would the dash gauge work), one of the relays or the fan module (which I have yet to locate). I do have an electrical tester (but am hopeless with it…) and a very basic OBD tool.

 

If the fan is on, then the computer "thinks" the engine is too hot; so either the computer has gone nuts, or something is feeding it false data.

If the fan is coming on with a cold engine, that's pointing to a faulty temp sensor.

You need to know the temperature of the fluid at the sensor, so you'll have to hook up a computer. Check autoparts stores, ask if they have such a device and check a temp like that for you. If not, you're probably better off buying a simple computer as a repair shop would charge more than the cost of buying one and they're nice to have on hand.

If removing the relays didn't kill the fans, then you didn't remove the right relay...lol. I don't know where your fan relay is, or if it even has one, but removing it would kill the fans, so you didn't pull it...it's somewhere else.

 

Welcome to the forum

 

Givin the year of your Mazda the first step is to scan the ECU for DTC(s) and you will find at least 1!!!
STOP unplugging parts and assuming anything until the first step in diagnostic trouble shooting is done. Continuing to guess and your approach is likely to make more problems than the original.

 

The local parts store was not able to help. I am trying to avoid this becoming an expensive fix so will hold off buying the computer for now.
Is the dash gauge fed from the same temp sensor? If so, wouldn’t the gauge always read hot?
As far as the relays go, I found it odd as well. I used the map on the cover of the fuse box and confirmed it online. There are 3 indicated. A main, a high speed and a low speed and I am pretty sure I removed the correct ones according to the relay map.

 

there is no check engine light but I will check for codes.
Thanks

 

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All OBDII and CANBus that have radiator fans will have a rely. These are generally always (with few exceptions) under the hood because of the higher power needed to support the circuit.
If you turn an engine on in early in the morning or very cold environments and set the defrost the fans will be activated.
On some models the ambient temperature setting can control the feedback to the ECU giving a faulty input signal that the AC is on and will activate the fans.
If the fan is activated the ECU does not always get input from any system that the engine is running hot to activate the fans. Example: turn your headlights on for about 20 minutes engine off then start your engine. The ECU will register that the battery is low and adjust the voltage regulator in some ECUs programs it also will activate the fans to keep all the temperature in check. the voltage to charge the battery
I would not suggest diagnosing yet using the measuring temperature of coolant. The procedure is a bit more complex, and you are leaving out HCAV system as a potential issue as well, the defroster will automatically run the AC compressor, and the fans will also be activated on many models so unless one knows exactly how to diagnose all those area's it is not a wise idea to go there yet.

Basically, in a nutshell ECU operating systems control from about 2002 problems require a bit more thought and also to build a problem-solving tree and not just random guessing?

 

Thats what DIY often say, but there is an area in the ECU called permanent file where an issue is placed and then as an example will check for correctness after serval cycles. During this period you may not get an activate check engine light. You can also and should look at the I/M monitors because the fans are indirectly related to those systems, and you are likely to find 1 or more in fault or not ready status.
The fan relays will have in some system 2 one for low speed and one for high speed. So if you found them you found the fan relays.

BTW rarely if the fan is working is it a faulty relay. I did say rarely so if the relay was super heated the internal the normally open contac may have been fused to the close position whcih the fans would constanly run every time the system has power to it. This is bad because the relay will super heat and could cause fuse panel or wire harness damage that can be very costly to service and repair.

 

All good advice, albeit some a bit more worrying than others….
i am admittedly a DIY but I had hoped this may be a common issue with a simple fix. Though I am still scratching my head over the relays.
My daughter lives a ways from me so I cannot scan it at the moment.
As a strange coincidence, she called me on her way home as she had pulled up to refuel next to another tribute an she could her that vehicles fans running as well so she in convinced that the fans running is normal….

 

In my world there is no such thing as a common issue except on forums with members posting as such. lol
If you consider very vehcle is different and very seldom have the same wear, operating environment and service record so how can anyone thing be common. If it were that easy. Then there are members that randomly change parts because they read advise on a forum or they find information they think relates to their exact issue. Or the DTC they read the part that generally it suggests is the issue and then start changing parts only to find it did not solve the issue.
If my Techs ever did that, they would soon be looking for a new place of employment. LOL The great thing about OBDII is the ease of stating if you are a trained and then experienced Automotive Technician there is no issue that cannot be found in an hour. I did say found not corrected, lol naturally changing some parts like an oil pressure switch cost retail 15 bucks but its location on a Ford F30 in a couple of years takes a booked labor time of 2 hours. ! hours to get to the sensor 1 minute to change the faulty sensor and another hour to reinstall all the parts to get to the sensor. Then the customer get upset when the estimate is 250 dollars labor and 20 for the part. Or I can charge them 125 for an hour's diagnostic fee which I if they let us do the work I don't charge. Most shops would have charged for the RR of the part and the diagnostic fee.
With this response I also advise and at time recommend that a DIY find an ASE employed service shop and pay the diagnostic fee for them to find the exact cause of the problem. Or a dealership service departemnt whcih will usually caost more for that service.