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2002 Honda Civic: 200k+ km, heat/a/c blower motor..diagnostic..circuit

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2002 Honda Civic, 1.7 DX w/air, 200k+ km, heat/a/c blower motor not working. When it failed we noticed no air blowing, turned fan knob, and it seemed to come on for a second more, then nothing. Self diagnostic circuit check returned no errors. Ordered Blower Motor via Installed, and still nothing. Fan knob seems to be working as it turns on the a/c light when in defrost modes. 12 volts at the blower motor plug - however, 12 volts all the time, even when fan is off.    11.5 volts while fan is turned off, key in in on (II) position, 11.5 volts fan on, key in on (II) position. 13.5 when car is running. Turning fan strength dial when key on produces no change in volts at the plug. All fuses look fine? I had tried to run the old motor off the battery and grounded as it is just a two prong plug, labeled + and - and nothing happened, so I figured it was the 12v motor.. guess I was wrong. What else could it be? Appreciate your help.


repalce the power transister((item B) it is bad this provides the ground you have power.



How the Circuit Works

The heater control panel controls the blower controls, air delivery, and A/C compressor controls automatically. With the ignition switch in ON (II), battery voltage is supplied through fuse 14. The control unit is grounded at G502.

Blower Controls

You can manually select the fan speed by turning the fan control dial clockwise, from the OFF position. Turning the dial further clockwise increases the fan's speed, which increases air flow.

Battery voltage is applied through fuse 14 to the blower motor relay contacts at all times. With the ignition switch ON (II), the blower motor relay in the under-hood fuse/relay box is energized which feeds battery voltage to the blower motor. The blower power transistor controls the blower motor in all speeds except HIGH. The blower power transistor is controlled by the heater control panel. When the control panel requests HIGH blower speed, the blower power transistor grounds the blower motor which connects it directly to ground, making the blower run at high speed.

Please Click Accept this is how i get paid, i can still provide instruction after

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Customer: replied 8 years ago.
I'm going to accept as I know the part you are talking about, but does not list it. I'll try to call Napa to see if they carry it.
ok let me know if you need anything else
Customer: replied 8 years ago.
The part has to be special ordered. Is there anyway to test the resistor or jump it to verify the ground issue?
yes backprobe ground on blower connector switch paper clip and wire to ground fan should come on with key on.
Customer: replied 8 years ago.
Received new resistor. Replaced the resistor with new. Still no fan. Tried all combinations of old blower motor and resistor and new blower motor and new resistor, it is neither of these parts. I was skeptical as I read if it was the resistor it would work on high, but I have no fan regarless of setting.
What else could it be?

i tell you what on high it still goes thru power relay that is how it gets it ground on high on medium on low and if you have power at blower all you need is ground tha tis what is wrong. did you backprobe to ground this would have verified this. check ground number g502


make sure you check fuse f14 and fuse 12




g502 under right side of dash


Customer: replied 8 years ago.
I did not do the backprobe as the part was going to arrive earlier than expected. Where can i find and identify g502?

Thank you.
see wiring diagram everything runs through the power transisiter. if you ground the black blue wire that blower should work.
reground the number 502 see if it works then, if it does make it permanent
Customer: replied 8 years ago.
Nothing. I even grounded the Blu/Blk from the Resistor and also the motor itself, while on, nothing.
I'm going to have to take it in, damn.

here is how it works if you have 12 volts at blower and you have a ground to battery that blower should work.


you say you have power hook a ground up to battery negative and back probe the connection it has to work.


hook the test light to the connection coming to blower blue and white should light keep it connected and touch the blu and blk if it lights you have ground and power.


no light on blue and white f14 and f12 blown.


if no ground it can only be one more thing that is the control head itself.


have them ship you one for 35 bucks worth the try may sure it is knob type or pushbutton be clear when ordering part, you said you turned the knob this listing is for the knob type, go to begining and choose pushbutton. -bin/search.cgi?userSearch=int&userPID=1000&userLocation=All+States&userIMS=&userInterchange=B%3E%3EB%3F&userSide=&userDate=2002&userDate2=2002&dbModel=


do not give up now i and you have spent alot of time on this , we can succed