RSX Heater Core Assembly - Teardown and Troubleshooting
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On my personal RSX, when I purchased it, the heat and AC weren't functioning properly. I verified that the heater and AC worked, so the problem was the vent system in the heater core assembly not moving to let the correct temperature air through into the cabin. The process of removing the heater core assembly is extensive, and requires removing the entire dashboard, so I decided to buy a $100 heater core assembly on eBay and find out what I think failed before I start pulling mine apart.
I made this YouTube video of myself disassembling the heater core assembly, and talking through the process as I figure out what went wrong. Below that, I have a bunch of pictures and descriptions of the parts. I hope you enjoy it!
My heater core seems to be “sticking”. I’m not sure if the motor is too weak, or what’s actually going on. The unit I purchased on eBay is similarly stuck. Here are some pictures from the outside.
Driver’s Side
On the driver’s side view, you can see the cable sheathed in blue plastic. This is the cable that connects the heater control valve in the rear of the engine bay to the plastic gears shown in the picture. The gears are connected to a small DC motor. When you adjust the temperature in the cabin using the climate control system, this part of the heater core moves, opening or closing the heater control valve. This either lets in warm coolant to the heater core, or blocks it off.
Circled is the Heater Control Valve, Connected by the Blue Sheathed Cable to the Heater Core Assembly
Passenger Side
The passenger side of the heater core assembly (technically housing, but who’s counting) is pictured above. The white geared plastic mechanism on the top left is responsible for controlling where the air goes. If you turn the dial to the footwell air path, the motor on this side of the housing turns, changing the position of the plate inside and directing the air towards the correct air vents.
The port on the lower right is where the heater core assembly meets up with the housing for the evaporator core, for the AC, and the blower fan, with the cabin air filter directly above. If you look to the left inside the port, you can see the heater core’s heat exchanger.
Rear, Toward the Firewall
The rear of the heater core assembly is where the system connects to the coolant supply. The two tubes come out through the firewall and meet up with the heater control valve hose, and then another hose on the rear of the engine block. The stud in the middle is used to hold the heater core assembly in. Towards the very bottom is a black plastic drain for moisture in the heater core assembly.
Top of the Heater Core Assembly
As I mentioned before, this is where the system turns the white plastic flaps to different positions to change where the air goes (defrost, floor, front vents, etc.).
The Blend Door Actuator Assembly - Removed
The blend door actuator, or as Acura calls it, the "Air Mix Motor Assembly", is a discontinued part, and there don't appear to be any manufacturers making aftermarket versions. OEMAcuraParts.com still has some though, as well as some Acura and Honda parts resellers. It's about $90 wherever you look. I just ordered a replacement, so I'll make an updated post if it works well! Updates below.
For what it's worth, the part number is:
Acura 79160-S6M-A41
The Blend Door Actuator Motor's Serial Number Information
An Overview of the Blend Door Actuator Motor and Gearbox
The motor is a Mabuchi Motor RF-370CB-11670. It's available on eBay through Chinese suppliers, but doesn't come with the plastic worm gear.
I received a new motor assembly in the mail, and immediately got to try and test it versus the one I assumed had become weak. They both appear to move the same distance and pull with the same force. This isolates the problem to the gears slipping or binding deeper in the heater core assembly.
It's also interesting that when adjusting temperature on the HVAC knobs, if you turn the temperature, it only changes the motor's position for 4 of the 14 notches.
Let me know if there's anything else you want to know about it!
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