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In my 2002 Civic, the interior fan stopped working. No warning, just stopped. A/C compressor still comes on when I turn the fan ***, but of course no air blows. All other bells and whistles seem to work too - Power Windows, Locks, Lamps, Horn, etc.. I'm pulling fuses trying to find one that could of gone bad causing the problem, but so far no luck. Wondering if anyone know for sure which fuse would handle the interior fan motor? Underhood I've got one labeled "Cooling Fan", but it looks fine.

 
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The fan relay or the fan itself could be the culprit as well.

 
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I've just had the same thing happen in my 2003 GLi Civic. One day my interior fan just didn't come on when I started the car (air con compressor will still run). I checked all the fuses under the steering wheel and they were all fine. Now I don't know if it is likely to be an issue with the switch, or the motor, or something else. Did you figure out what was the culprit in your case?

 
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Quite often it is due to the "transistor" failing, or as I have read an as of yet unidentified component on the transistor unit opens up.

It is a 2 lead device I think to be a TCO ??

Still waiting to find out what it is if anyone knows post up.

A TCO should have a temperature figure, usually printed on the body of it.

 
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Thanks Craig, you were right on the money with that suggestion. The problem was a failed TCO (thermal cut out) in the transistor (just under the glove box). The part had a number N109 written on it, and a cut out temp of 114degC. I had a bit of a search and found the following data sheet for it:

http://www.mouser.com/catalog/specsheets/XC-600225.pdf

I replaced it with a diferent TCO, which cost me $3.50, but I found I had to insulate this one, becuase it had a conductive case and the heat sink was already attached to the drain pin on the transistor (I learned this the hard way when after soldering everything up and installing it, my fan would not turn off). The original TCO doesn't have a conductive jacket, so this wouldn't be a problem if I used something similar.

Just a note, to replace the TCO, you have to desolder the three transistor pins and the two TCO pins to remove the PCB.

Also, an easy way to test the fan motor itself is to remove the plug from the transistor and short out the power circuit (the two thicker wires) then turn on the ignition.
If the fan doesn't turn on, test the positive power pin on this plug for 12V with the ignition on to confirm the relay is working.

If you are still stuck, here is some helpful information that I found on another forum:

"There is a relay that operates the heater blower motor in the engine compartment in the fusebox right side looking into the engine compartment. The heater blower relay is the largest relay in the middle of the top or bottom row. Fuse 12 (40Amp) in the engine compartment fuse box supplies power to the relay, fuse 14 (10Amp) in the passenger compartment fuse box must also be OK for the blower to work. Power should be at BLUE/WHITE wire with the ignition key on . BLUE /BLACK gets grounded through the blower motor resistor and heater panel switch. The blower motor resistor is behind the glove box to the left side."

I hope someone will find this helpful

 
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Good info, thanks for posting the results on the TCO that is the value that I had seen listed but had not confirmed.

This is pretty common on the 7th gens.