Blend Door

[FrostyCd5]

Does any one have any idea of where the Blend door for the heat/ac is located or what it might look like in a 97 accord? Thanks

[HondaGuy1212]

I believe it is located right underneath the throttle body. If you take off the intake tube you can get access to it. It's like a valve with a cable attached.

[TomQuick]

Well, I think it is in a completely different place than HondaGuy does, so one of us is very wrong.

I think it's under the dash, passengers side, behind the glove box. If you are having problems with where the air is going, it's likely either the mode control motor, or the control panel, and there is a test procedure you can follow to determine which one is the problem.

[cp[mike]]

hondaguy is thinking of the heat control valve...

blend door is a flapper that moves back and forth to redirect air, and is part of the heater core behind the center of the dashboard, youll need to dig in most of the way to get to it. tomquick is right, its more likely the electronics related to it instead.

[TomQuick]

Mine doesn't like to switch over to the dash vents. It will do the dash/floor fine, but takes playing with the switch many times to get to dash only. I haven't gotten around to troubleshooting it yet, but I looked into it, and know it's likely either the stepper motor (I don't think that's the problem) or the control panel on the dash (where I think my problem is).

OP, let me know if you need a quick run down of the test procedure for the switch, and motor.

[FrostyCd5]

Thanks for the responses.

Last winter I had trouble changing it back from A/C to heat I manualy switched it from heat to A/C by turning the the thing under the dash and turing the heater valve in side the bay but I still got no heat. I then replaced the heater valve thinking it was broken but no then i replaced the thermostat but still no heat then proceseed to bleed the cooling system and still no heat.

I then took it to a shop the tech stuck his arm under the dash fiddled with something but got the heat working. He said something was broken but he could not tell me what he said he had to remove part of the dash to be able to tell see what so to bring it back another day (not on a saturday). This costed me 60.00

I never brought it back and now i need my A/C as it it 85 out side and i am tiered of driving my winter beater (even though it has A/C).

Any ideas you guys might have to get to the root of the problem would be great.

[TomQuick]

If I had to guess, I'd say it's either the switch panel in the dash that isn't working right, or the motor for the blend door is not working right. Since the mechanic said he'd have to take apart the dash, I'd say he was thinking it's the motor, but I'd still do the diagnostic to be sure.

Under the dash, passengers side, you should be able to find the big black plastic box, that is your heat and A/C box. Toward the drivers side of the box you should see the mode control motor. It has a wiring harness going up into it from the bottom. Remove the plug, and look at it with the open ends facing you. The wires, from Left to Right should be:

BLK/YEL BLU BLU/RED YEL/GRN LT GRN/BLK LT GRN/WHT LT GRN/RED

Turn the ignition switch to the on position, and measure voltage between the BLK/YEL terminal (+) and body ground. If there is NOT voltage, look for and repair a break in the BLK/YEL wire between the under dash fuse box, and the mode control motor (check the fuse first)

If there is voltage, turn ignition off, and test mode control motor (INSTRUCTIONS BELOW).

If the motor is NOT ok, remove motor, check the linkage and doors for smooth movement, and repair as necessary. If the doors / linkage are in good working order, then replace the mode control motor.

If the mode control motor IS OK, remove the heater control panel, disconnect the heater control panel 14Pin connector. Check the following wires for continuity to ground: BLU BLUE/RED YEL/GRN LT GRN/BLK LT GRN/WHT. If ANY have continuity to ground, look for, and repair the short to ground in that wire between the heater control panel, and the mode control motor.

If NONE of the wires show continuity to ground, check the same wires for voltage. If any of the wires show voltage, look for, and repair the short to power in that wire between the heater control panel, and the mode control motor.

Check each of the following wires for continuity between the Heater Control Panel connector, and the Mode Control Motor connector: BLU BLU/RED YEL/GRN LT GRN/BLK LT GRN/WHT LT GRN/RED. If any of them do NOT show continuity, look for, and repair the break in that wire between the Heater Control Panel, and the Mode Control Motor. If all the wires show continuity, replace the Heater Control Panel.


MODE CONTROL MOTOR TEST: Remove the 7 pin wiring harness from the mode control motor. Looking at the wiring connector on the motor, with the latch at the top, the wiring pins are 1 2 3 4 5 6 7.

Using a jumper wire, connect +12v to the number 1 terminal, and ground the number 7 terminal. DO NOT GET THIS BACKWARDS! Now, using a jumper wire, connect the number 7 terminal individually to the number 2, 3, 4, 5, and 6 terminals in that order. Each time the connection is made, the mode control motor should run smoothly, and stop.

If the mode control motor does not run when jumping the first terminal, jump that terminal again after jumping the other terminals. If it runs when jumping the first terminal again, it is working properly.


If the mode control motor does not run on all terminals, remove the motor, and check the linkage and doors for smooth operation. If the doors and linkage are in good working order, replace the mode control motor.

I know that is long and complicated, but print it out, and follow it carefully. If you are unsure of anything, ask questions before you do it. If you do this properly, you will find your problem on the first try, and not have to throw parts at it guessing what the problem is.