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Working on my sister's 02 civic, and blower motor is not working. Checked with test light and confirmed power to motor even when switch is in the off position. I'm assuming the negative lead is switched for operation. Ran a jumper from what is presumably the negative lead to ground, and the fan operated fine. Fuses seem to be good as well.

Did some searching and came across a seemingly common transistor problem, but based on what I've read, if the transistor was bad, the fan would at least work when turned to full speed. Fan doesn't work at all.

Any ideas? Thanks!

 
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Yeah, hondas run a negative switch on most of their stuff. If there is power to the fan once you bypass the ground, it's probably the switch itself in the climate control fascia in the dash. They are also a common problem.

 
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any surefire way to test the switch to ensure it is indeed the problem? I'm assuming I could play around with it with a test probe to figure it out...

Also, any good recommended sources for a replacement? Is aftermarket available, or is the dealer my only option?

 
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I think you've pretty much isolated it already by testing the blower motor directly. Best thing to do would be to hit up a junkyard or car-part.com, which is an online junkyard search engine.

 
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So I picked up an entire switch/bezel assembly from a junkyard for $75 and swapped it in... no dice. Blower motor still not working. Switched back and forth between original and replacement, and noticed they both did the same thing... If the A/C is toggled "on" the the light on the A/C pushbutton will light up and the condenser fan will briefly run. Switch seems to be sending some info to the system.

This brings me back to the transsistor. I've read that if it were bad, the blower motor should still work with the switch turned all the way to the right. I'm not getting any such activity. Assuming that the blower switch (****) is good, and knowing (see above) that the fan is good, what other than the transistor can be bad?

Thanks for your help thus far.

 
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Here is some information on the system. I would try the Ohms test, The other test is up to you. Sounds similar to what you already did. You could try doing the transistor repair thread diy and see if it makes any change in the symptoms.

If I read correctly it said that the high speed was also controlled by the transistor. ??