Picked up my first 06 civic hybrid with 90k miles. Car worked fine until recently, the IPU fan aka cooling fan for the battery has been acting up.

When I turn the ignition to the on position without starting the car, the fan will pulse on and off. I opened the trunk and gave it a listen and the fan will get up to speed for a few seconds, then slow down. This process repeats over and over. Once I start the car, the fan will run on full blast. After that there is no issues whatsoever or any lights illuminated on the dash. No IMA light, No check engine.

I scanned the car with an obd2 reader and found a low voltage 61-1 but no check engine light. I hooked up my multimeter to the battery and found it fully charged at 12.4v. However when I turned the ignition on, the fan began its pulsing and the 12.4v battery voltage dropped to 10v. When the car is running, the battery operates at above 13.5v. Battery is new btw.

Doesn’t seem normal at all, the fan never did this for the past 5k miles I’ve put on it since I got the car.

Was wondering what exactly controls the fan so that I could get it replaced, or is it the fan itself that has failed?

Any help is appreciated, thanks.

 

Red Herring.

Fan blows when it's hot. You definitely need a new 12V. Fan pulls about 8A with the rest of the car pulling somewhere around 20A briefly. That shouldn't cause a 12V to drop to 10V.

All signs point to a dying 12V or one that is never getting fully charged. Honda does not manage their 12V charging very well, so it's not uncommon.

IMHO, replace with the larger 51R instead of the stock 151R. 40% more capacity. You will have to discard the plastic shrouds, but it will fit.

 

I have a feeling you’re right. Right after this post, my gf took the car to run errands. Car wouldn’t start when she got to her destination despite driving for at least an hour..was able to start up a few tries later with the ima assistance. Once she got home, I stuck a charger on it. It only charged for about 10 min and the charger shut off..seems too quick of a charge to me so I hooked my multimeter up and found it was holding maximum 11v now.

I’ll for sure pick up a battery tomorrow and give an update. I couldn’t find any 151R at Walmart earlier so I’ll definitely give that 51R a go.

Thank you for the input Kieth.

 

Dropped in the 51R battery. Voltage with ignition on is now above 12v! Weird how a battery just a few months old quit early.

51R>151R Nuff sed

Still not sure about the IPU fan running on full blast even though the car has been sitting overnight and cold. But at least I know it’s running and I’ll know for sure if it isn’t when it stops.

thanks for the help.

 

Has a grid charger harness ever been installed on this vehicle?

 

Not that I’m aware of. I’m the 3rd owner. The IMA battery was replaced under warranty before I got it. That’s the only major component that I know. I don’t see any harness or plug in the trunk or between the seats.

 

Installation of a Maxx Volts harness can cause IPU fan controller malfunction even after removal:

https://www.greenhybrid.com/forums/f...tml#post270042

As I recall, there were 3-4 complaints of it on this forum.

 

Is the BCM something that can be swapped between vehicles, plug and play? That actually sounds like my 2nd problem.

 

Yes. Note that the cooling system of the HCH2 is horrific. Failure rates of 06-08 were 2X as high as 03-5 and due to additional mistakes, 09-11 failure rates were 2X worse that 06-08. HCH2 has the distinction of having the two worst hybrid batteries ever made.

Additionally, the Sanyo cells in the HCH2 are IDENTICAL to those in the Ford Escape Hybrid - one of the BEST hybrid batteries ever built. Why the difference? Escape has rear A/C dedicated to the battery. Cooling.

IMHO, I would personally rather replace a worn out fan than a overheated battery. I often contemplated shorting the PWM line to ground to force it to run all the time, but that's not always good when the interior air it's sucking in is 140°F like it can be here in Phoenix. Optimally, I would have wired in a manual switch to ground the line. Maybe that's your best solution... replace BCM and wire in your own switch.

 

Wiring a switch is actually not a bad idea. Since the switch is wired as a short to ground, it shouldn’t affect the BCM in any way right? Like any voltage sent through that PWM wire isn’t going to back travel to the BCM and fry it again?

Im actually considering that idea when I do swap the BCM out. But I don’t want to end up at square one with another bad BCM.