2008 Accord Blend Door/Air Mix, Heater problem

[Brybo86]

So this winter my wife has been driving our Honda, recently she told me that the heat isn't very hot. The car has electronic Dual Zone climate control.

I told her that was normal and Honda isn't known for their great heaters.

The heat in my Lexus on the other hand can burn you if you are lucky enough to put your leg by the vent.

Well drove we the Honda to church today and sure enough the driver side vents are lukewarm at best.
The passenger side vents in the middle, side and floor all put out good "Honda heat"
Their is great airflow through both vents. A/C works well on both sides.

I drained the coolant and refilled with genuine Honda blue coolant about 60k/3 yrs ago.

I have been googling everything from clogged heater cores to blend doors to mode actuators.

I don' t think there are 2 separate heater cores just a shared one. I can't imagine it is clogged since the passenger side heat works well.

So I'm leaning towards the blend door/actuator but I cant find and info about how to change this or even where it is located (besides somewhere behind the dash). On my Lexus there is a manual cable-controlled heater valve on the outside of the firewall. No such thing on the Honda.

I need some advice.

 

[Recalculating]

I do not have this issue with my CR-V however I have the exact issue with my GM BPAU.

I have read about this GM problem & fix with a possibility being the battery was disconnected when the dual climate contro was still on. This apparently can change where the actuators park. When the battery is reconnected, the timing of the actuators are out of sync. One suggestion is to turn the climate control off and disconnect the battery for ten minutes. Reconnect and turn the climate control on so it relearns.

Almost sounds like how the transmission relearns it's shifting patterns but guess they use actuators too.

I will try this soon and if not a fix, will likely purchase the blend door actuator. I've had it out and looked at it with no signs of broken internal parts. We'll see.

 

[Brybo86]

Today I played around with the heater controls and temp settings. I watched under the driver and passenger footwell and looked at the air mix actuator as I moved the controls. They both are moving perfectly stop to stop. Driver side is still cold, passenger side hot. I drained coolant and heater core and refilled with Honda coolant. Same issue afterwards.


I guess the newer CRV's like 2012 to 2013 had a tsb 14-063 issued which address clogging heater cores... Dealer Fix is a 2 hr long flush using CLR, a 5 gal bucket and a water transfer pump

after that they flush with straight water for 30 mins
then reconnect coolant lines refill with coolant run engine for 30 mins
then drain and fill coolant again

I wonder if this same issue is the problem on the 2008 to 2011 models even though they haven't released a tsb for it....?

 

[Mau]

Reverse flush the heater core. Use CLR and I would flush out the coolant and use Honda Type 2.

 

[dishdude]

But if the heater core is plugged, why is the passenger side heat okay?

 

[Brybo86]

Originally Posted By: dishdude
But if the heater core is plugged, why is the passenger side heat okay?


Exactly, those were my thoughts as well...?

This morning I removed the blend door actuator and everything seems fine, door moves freely and when closing it quickly I can hear that "thump" like when you change temp quickly in cable operated setup.

 

[artificialist]

Originally Posted By: Brybo86
Originally Posted By: dishdude
But if the heater core is plugged, why is the passenger side heat okay?


Exactly, those were my thoughts as well...?

This morning I removed the blend door actuator and everything seems fine, door moves freely and when closing it quickly I can hear that "thump" like when you change temp quickly in cable operated setup.

Perhaps there is more sludge in one side of the heater core than the other. That could result in uneven temperatures.

 

[Brybo86]

I'll begin the post by saying ... I FIXED IT!

I used the method described in the CRV TSB that i noted in the original post.
Here is a run down
Supplies used
one 1/2 HP Utilitech transfer pump from Lowes $110
3 10ft sections of 5/8in I.D. clear vinyl tubing, 49 cents per foot, $15
2 brass hose connections 5/8 to 3/4 garden hose to go on either side of the pump. $10
1 new 5 gal bucket $2
4 total 7/8in O.D hose clamps from the connection to pump and to heater core, $3
2 28oz bottles of CLR $10

This is the picture from the TSB, My setup looked the same as this but I didn't have the filter part.

Pump and bucket setup.

connections at heater core, I started with the connections circulating as the engine would do for about and hour and then later switched it and did reverse flush for about 45 mins.

While running CLR mixture

While running CLR mixture. Turned into a cream like color and consistency.

after an hour, mixture foamed up and almost filled the bucket.

close up, not sure what this stuff was on the foam, obviously dark but didn't feel oily

I didn't take a pic but at the bottom of the bucket there was about a 1/2 teaspoon of grit collected. dark black particles similar to sand in size. I didn't have a filter and when I stopped the pump I could see a few small particle suspended in the water while flushing, So i think more stuff was dislodged then I could feel because much of it was suspended in the solution.

after this I flushed with straight water, about 10 buckets full

here is a quick video while flushing with water


blew the heater core out with air and refilled with coolant.

Heat works equally on both sides now...!

 

[dishdude]

Glad you fixed it! But man that's a weird one for a heater core that new to get plugged, and only have an effect on one zone!

Any idea what causes this? I would think the radiator would also have issues down the road.

 

[Brybo86]

there is 105k on the car but I have drained and refilled coolant with honda OEM stuff at 45k, 90k and now 105k

the CRV TSB talks about casting sand that was left in the block somehow...?

 

[Vikas]

I am not understanding the reason for going through this elaborate setup. What was wrong with plain garden hose method? And how did your pump like pulling the CLR through it for an hour? Most of these pumps can't handle caustic liquids.

 

[Brybo86]

i used this setup because it is what the TSB described.
the pump is what the Honda dealers use.
we'll see
TSB

 

[mongo161]

Thank you for your post and video. Great Work! Sure beats my setup with a connection to the home hot water heater tank and using powdered automatic dishwasher detergent to unclog the heater.

 

[Vikas]

That pump is *expensive*! Does anybody know a cheaper but equally capable pump (110V)? I see bunch of Chinese 12V on ebay but they will not do this job.

I do wish you had tried plain garden hose + CLR method first before buying the $110 pump. That way we would have known for sure that the pump was absolute must for this job.

 

[mongo161]

Well, you can always use the pump to exchange ATF by pumping in clean fluid and letting the old flow out through the cooler line to the radiator or torque converter, pumping in new ps fluid, it may even be strong enough to pump in gear oil for the diff's and transfer case.

 

[DoubleWasp]

That's exactly the procedure I use on scaled up marine heat exchangers, but I use Bright Bay Hammerhead Marine Descaler. CLR is cheaper, though.