I am new to this forum and just purchased a 2007 civic ex. My only previous Hondas were 4 of the original '72 AZ600 coupes. My issue is the a/c vent fan sometimes takes a few minutes to turn on after starting the car. This happens maybe after 20 or so sucessful starts. It doesn't matter whether the fan is in off position while starting the car or in the on position. Any ideas?

 

My guess is that it is a defective switch or loose ground wire to the fan. If you were able to test whether 12V was being sent from the switch when the switch wasn't working, you would know if the switch is intermittently bad or whether the fan is bad or has a loose ground wire.

The next time the fan doesn't come on, try turning the switch on and off a few times. If the fan suddenly comes on, the switch is most likely the culprit.

 

I think it'd be like the earlier "modern" models (1996-2005) with electronics in the control panel and a power transistor driving the fan, but would need to pull a diagram to be sure. Intermittent problems are always hard to troubleshoot since you have to test while the problem is occurring. A major check is to measure voltage across the fan motor. If you have voltage but the motor doesn't run, it is bad. Worn out motors often become intermittent first.