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

17287 Views 41 Replies 8 Participants Last post by  Soulrazy
From evidence on the web and multiple threads on here we can see this IMA fan failure is not uncommon. :cry:

So the $$$ question is can we fix the FAN instead of replacing it? :unsure:

The supply of junk yards fans will likely dry up at sometime and a new one is UK £300.
Cheaper in the US I understand ~$160?

To find out I will need someone to send me a broken one to disassemble for the benefit of the CR-Z community.

Any offers?

The fan failure is often associated with blown IMA 12V fuse 53 which indicates some sort of short circuit.
Is the failure in the motor itself or in the fan drive module attached to it?

We could find out with a dead fan donation.... ;)
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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. ;)
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Some IMA fan repair options and ideas including substitute fan modules from other IMA cars. (y)

I still need a broken fan module from a CR-Z, the motor and board to try and fix.
Don't need the outer case etc. Thanks if you can help.
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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
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You can test the fan with the HDS. Did you do that?
It should go through the three speeds. Low/Medium/High.
It's in the IMA adjustment section IIRC.

I have a spare fan innards for £50 exchange + postage.
I would want to look at the old one so you have to send me that once you have swapped them over.
The IMA usually commands the fan to max speed if there is an IMA fault in case it is an overheating problem it is unaware of.

Sounds like you will def have to change/fix it.
Some more linked same fan repair info on another forum.

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Do you have an OBDIIC&C plugged in?
Does that fault occur without it plugged in?
If the code does not reappear let me know what OBDIIC&C firmware you are running.

The OBDIIC&C firmware does have the capability of controlling the IMA fan, so it may be a conflict between what the OBDIIC&C is requesting and what the car (MCM) is wanting.

I suspect the MCM does not monitor fan speed unless it is being commanded by it.
But if it is commanding 25% rpm and the OBDIIC&C is demanding 50% rpm that might give rise to a conflict and code.

The reason we might not have seen this before is that the temps have been so low in UK no one's fan was running LOL. :unsure:

Of course this might be a red herring and you have a real IMA problem.. :cry: Can't remember if you have an HDS?
It's easy for bugs to creep in with a complicated gadget like the OBDIIC&C :rolleyes:

If you go into the menus make sure FanStart is off (0) in Config Screen 4.

It's probably on (1) which is causing the problem.. Doh...

I'll add it to the bug list!
I added that function to keep the IPU cool in my 21kw supercap setup so it started running earlier.
Maybe not such a good idea now the weather is warmer. LOL
I have refunded the fee for the exchange fan.
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This is the wrong forum for the 2005 Accord hybrid.. However...

Did you clear your old IMA fan code properly after installing the new fan?
If not it might still be there waiting to be read.

P0A7F is IMA battery deterioration IIRC so you have more than just a possible fan problem.
As your IMA battery is bad, it is shutting down the DC-DC so the 12v battery is not being charged, hence losing AC, steering and car stalling etc.
You need to fix the IMA battery, speak to Bumblebee batteries in the US.

Have you checked for things like blocked IMA inlet and outlet vents.
Mice make nests in weird places. If the code really has come back try and get a proper fan from a breakers yard.
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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. :eek:
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.


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You cant wire the fan to run permanently in the car as the computer checks the speed and will throw a fault.

The MOSFETs can be checked for basic continuity once the circuit pcb has been removed from motor. MOSFETs are attached to the silver heatsink.
My far eastern cheap mosfets arrived and I replaced the duff item and the fan now appears to work on the bench. (y)

I might swap it into my test car to see if it faults when under car control.
It's a two minute job to swap it out with all the interior removed.
I can carry the known good one with me and swap it at the roadside if need be.
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Maybe something else on the board failed or perhaps more than one mosfet but in a more subtle way or the motor windings were bad.
Unfortunately it's a common problem and they are clearly not a great design.
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I have just been fixing another failed IMA fan today from a UK owner. :rolleyes:

This one had two mosfets that had failed short circuit on one of the phases of the bridge allowing a direct short between 12V and GND.
This causes fuse 53 to blow immediately disabling the IMA system and not giving the normal P1448 fan code because the IMA 12V side has no power.
I have replaced the two blown mosfets and it now seems to be working fine on the bench.

So if your fuse 53 blows immediately it is replaced, unplug the IMA fan.
If it no longer blows the fuse with the fan unplugged then you have located the fault.

I think I will offer an exchange repair service on the these fans in the UK for £110.
If your fan dies you contact me I send you one the next day.
You post your dead one back to me when it has been swapped out.
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Table Interior design Office equipment Wood Engineering

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...
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Same part for a USDM car?
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So what are the common failure modes for the 3 phase BLDC (Brushless DC) IMA fan?

Product Font Rectangle Parallel Pattern

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.


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.
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