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Old 12-13-2008, 10:20 PM   #5
Scooby Newbie
Member#: 57993
Join Date: Mar 2004
Location: Saint Louis MO
2004 Impreza WRX STI



I'm working on the same exact issue on a 2004 STI right now.
Unfortunately, we have different part numbers on stuff, but I can probably help a little.

You need access to a voltmeter/multimeter to do this.

Even a cheap one $20 would be good enough.

I'm working on a write up, but I'll give you what I have currently..

You can probably move the passenger seat back and flip upside down to do this without removing the glove box (removing the glove box only takes 5 min).

You'll probably see 1 wire bundle going directly into the blower motor toward the right side of the blower motor enclosure, and 1 going to the left side to the rear,(this is the blower motor resistor or blower power transistor, a little white? plastic thing) depending on if you have manual or automatic climate control.

Kelly’s Diagnostic results
My fan is not working at ANY blower motor setting.

It was intermittently working, (rarely), but when it did it was on all speeds. It would sometimes work after hitting a bump in the road. So if Iwas cold, I would just drive down a bumpy road. (Just Kidding).
First things first, in Subaru’s definition, a “manual” climate control is something that doesn’t have an “auto” setting on the blower control!! This kind of goes against my definition of a much fancier standard of what an automatic climate control is, but I accept this ; ).
In “manual” blower motor controls, you have a blower motor resistor and in “automatic” blower motor controls, you have a blower motor power transistor, in Subaru’s terminology.
Since the 2004 STI has an auto blower motor setting it has “Automatic Climate Control” and therefore a blower motor power transistor.
The reason I’m stressing this is that in the 2004 WRX/WRX STI shop manual they show the incorrect part for an STI, a WRX blower motor resistor that costs $40.00 retail vs the STI blower motor power transistor at $300.00 retail.
The correct part number for a 2004 WRX with manual climate control is
72 226 FE000 and costs $40.00 retail

The correct part number for a 2004 WRX STI is

Remove the blower motor power cable that plugs directly into the blower motor
Take the test leads fo the multimeter set for DC Volts and touch the test leads into the power connector to measure the voltage. If the voltage shows a negative value , the leads are backwards. Switch the leads and measure again. You’ll get the same answer, but without the pesky negative sign. And this doesn’t hurt the electronic system either.
On my 2004 STI the power connectors look like the letter T rotated 90 degrees to the right like __ |
On my 2004 STI the left Horizontal one is Negative, and the right vertical one is positive
This is what I found.
I’m testing with the existing blower motor power transistor in place
With accessory power on, and vent position on upper only, (defrost position decreases the values by 0.4V.)
I tested the voltage at different blower motor positions to see what I found.

Power at the blower motor harness was
Blower Motor Fan Switch Position Voltage
Off 0V (As expected)
Position Auto 11.7 – 12.1V
Position 1 4.7V
Position 2 6.5V
Position 3 9.5V
Position 4 11.6 - 12.1V
Auto and 4 appear to run directly to the fan, not going through a power transistor. The blower motor is receiving 12V on these settings, this means that for testing purposes you can run power directly from the car battery in to the blower motor and, (if you connect it properly), you won’t damage it.
Blower fan settings 1,2,3 all go through a power transistor as shown by the lower voltages on those settings.
Theoretically, blower fan setting 4 and maybe even auto should work with the resistors blown.
So if it your fan works on high speed, (blower fan setting 4) and maybe even auto the blower motor resistor could be the reason.

In my case..
The conclusions I’m making with the results that I have so far are…
Since I’m getting, voltage, I know that the fuse is good.
I don’t know if I can also say that the relays are OK. But I believe that the relays are OK.
Since the voltage is changing, I know that the fan speed switch is good.
Since the voltage is changing, I know that the blower motor power transistor is probably good also, but since there are signs of burning in the connectors so, I’m going to replace the blower motor power transistor also.

If you remove the blower motor power transistor, and retest the blower motor power harness you get 0V as you would expect.
I would say at this time it looks since we are getting variable voltage to the blower motor, and it doesn’t work, it’s probably dead.
Since the blower motor runs at 12V you can run wires directly from the battery to the blower motor, if it doesn’t run easily or at all, it’s probably dead.
Normally, they tell you to take it out of the plastic enclosure as in the old days, but I believe that there’s no need to in this case. (This is my personal speculation by looking at it.) This is something I will verify when I tear it apart.
Subaru sells the entire blower motor enclosure and motor as a single part for $300.00. There are no replaceable parts inside according to Subaru.
That is the “official” fix.
Buy the entire blower motor enclosure and replace it.

Since it doesn’t matter I’m taking mine apart and working on a more old school/ hacker approach to fix it or just replace the motor itself, or the whole enclosure for $300.00. More on that as I fix it or not,
So, do you replace it or can you go to an electric motor shop and rebuild it with new brushes?
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Last edited by kcarpent; 12-13-2008 at 10:38 PM. Reason: forgot something
kcarpent is offline   Reply With Quote