P1448 Bad IPU IMA Hybrid Cooling Fan Motor ... Can it be fixed?

Picture nicked from a Thai? YT P1448 video showing a blown fan drive MOSFET. (Thanks Jamie)



Looks like someone might have had the same idea.
Doesn't really say if they fixed or just replaced the module.

Worth replacing the blown mosfet to see what happens.
We might get lucky and it hasn't damaged whatever drives the mosfet further back up the line.

Can get ten for $5 on fleabay. (Newer better parts are also available.)


So I need a blown fan module from someone to play with.

From the CR-Z workshop manual.



Pin 1 is GND
Pin 2 is PWM Drive in
Pin 3 is tachometer out
Pin 4 is 12V+

You need pwm input on pin 2 say Freq 2khz (The low duty % will determine the speed)
I haven't actually checked the pwm freq that is an educated ballpark guess.

If you simply connect pin 2 to gnd the fan may run at full speed.

Bridging the tach and pwm wires may make the fan run if you start it off with your finger so the tach output is pulsing

I recently got a bad fan back from a UK CR-Z owner who had the P1448 fault.

This video shows good V bad fan bench test using a 12V current limited power supply.


Note the bad fan may not move at all in this test, and visual inspection might reveal clearly blown mosfets. (This fan did not have obvious visual mosfet damage)
Anyway after removing the pcb from the motor and testing the bad fan 6 x mosfets with a multimeter on basic continuity, it shows a blown (short circuit) mosfet that I have now removed.

You can buy them on e-bay for $5 for ten so it should be a case of simply soldering in a new one and off we go.
Note the solder on the PCB is high melting point. I had to turn my soldering iron upto 480C before it would melt properly.
Careful you don't mangle the pcb traces.

The NEC K3755/2SK3755 mosfet is a slightly narrow TO-220 insulated body type and I don't have any suitable in stock, so will order some and report back when fitted.
Might be a while on the slow boat from the far east. Note you could use any compatible pinout similar spec N Channel part.

Data sheet attached.

I now have three fixed IMA fans in stock for UK/EU owners if needed.

I managed to repair the latest one just now by replacing two mosfets.
These had not completely failed but were bad enough that the fan would not start occasionally depending on where it stopped.

The fan driver times out after a few seconds if the fan does not start rotating, probably to prevent damage to the drivers if the impeller is locked.

So this could/would cause an annoying intermittent P1448 as sometimes it would start and other times it might not.

If anyone in the UK has a dead IMA fan sitting around please send it to me. Thanks...

So what are the common failure modes for the 3 phase BLDC (Brushless DC) IMA fan?

My examination so far of a few dead fans shows the failure is always in one or more of the 6 Mosfet Transistors on the metal heatsink.
These are labelled SW1-6 in the generic image above.

We currently have two distinct failure modes...

1) If just one of the six power Mosfets fails then the motor may still work to a degree but.....

a) It may not be able to start depending on where the impeller stops. (The fan driver times out after a few seconds if it does not start rotating)
b) It may not reach the correct speed (rpm) due to lack of power from the blown Mosfet section.

(This is why some owners report they can hear it working but still have a fan error code P1448 and no IMA function)
The fan has a speed sensor feedback circuit, and with a certain drive power the MCM expects it to reach certain set speeds (rpm)...


2) If two Mosfets have failed short circuit (allowing current to flow when not commanded)
then this can set up a direct short circuit between the + and - power feeds which immediately blows the under dash fuse 53.

The system is unable to detect this as a fan fault and set code P1448 as the power to the MCM/BCM is lost when the fuse blows.

Conclusions.

If the fuse is immediately blowing and you have no fan related code then it's likely two or more fan Mosfets have failed.
Simply unplug the fan and then replace the fuse to confirm if it is responsible.
If it doesn't blow with the fan unplugged you have the answer.

If you just get P1448, sometimes intermittently and the fuse does not blow, then it's likely one Mosfet has failed or is failing.

Visual detection of which one/s has/have failed is sometimes possible if the Mosfet package has been damaged. (Blown/burnt)

Of course there may be other rare failure modes we haven't encountered yet, but I suspect the above covers 99% of them.