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Discussion Starter #1
My mazda 6 V6 2003, none of the fans work, not even the fan for the AC condenser.
I did replace the FCM, but still doesn't work.
I did check the PWM coming out of the PC. AN I don't see any signal and the voltage is almost zero.
When Turn On the AC I see a very small signal, around .2 volts p-p.
Any Ideas?
 

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Maybe try/test the relay for the fans? Did you check the fuse?
 

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Discussion Starter #3
Yes, the relay supply 12 volts to the FCM,
the PWM comes from the ECM.
The PWM is only .2 v p-p.
 

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Do the fans turn on as they should without a/c?
 

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Discussion Starter #5
They don't turn on at all, I know they should turn on whe the AC is ON, but they don't
 

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How about checking to see if the fans work? Have you tried jumping 12v to them directly?
If that doesn’t work, I’m guessing either the fan controller died or the ecu has a problem directly or indirectly.
 

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Discussion Starter #7
They work! The ECU does not produce a PWM.
That's the problem.
Why doesn't?
Need some ECU troubleshooting procedures.
Thank you, do you have some references?
 

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The PWM isn't produced either because of a number of possibilities that I can think of:

1) The ECU senses it does not need the fans.
2) The A/C infact is not on, despite what the controls are set to. IE The climate control is set for it to be on, but the compressor is not running because of the lack of refrigerant or possibly the temp sensor in the Evaporator has malfuctioned. Other possibilities would be the compressor trigger line/clutch wire has a break/no continuity
3) ECU/ECM has malfunctioned
4) Exterior ambient temp sensor is not plugged in or malfunctioned.

So you might want to check these items. Make sure the A/C compressor is in fact turning with clutch engaged and not just free-wheeling the pulley.

I'm guessing this means your engine is also overheating?
 
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