The air conditioning blower motor stopped working this past summer (worst timing ever). I took it out, put it back in, and it worked again for a day before dying for good. So, I ordered a new one and replaced it. The replacement was working fine for about 5 months, but it then began exhibiting the same problem as the original: it wouldn’t come on until after I’d been driving for a while. The new unit never made any unusual noises while running (the old one got noisy just before I replaced it), but now it isn’t coming on at all. I find it hard to believe that the replacement blower motor has failed after only 5 months. What else should I check?
The next time the blower motor doesn’t work, set the fan speed on high and rap on the blower motor with the handle of a screwdriver.
If the blower works, you got a bad blower motor.
+1 to Tester’s suggestion.
If that doesn’t help, you could check the motor plug for 12VDC with the switch on high. I believe the plug contains both leads (two wires, not a chassis grounded motor housing), so checking it should be pretty simple once it’s unplugged.
You might also want to try changing the fuse. It’s not common, but I have seen a failing fuse become intermittent. It’s worth a buck to try changing it. The owner’s manual should tell you where it is.
+2 to Testers suggestion, but if the motor comes on when the moment you put it in high, then the resister pack that controls the blower motor speed is probably bad. The highest position is a straight through bypassing the resistor pack.
The blower relay is another possible culprit. Proper trouble shooting is the best way to find where the real problem is at. Most systems supply power to the blower motor via the relay and place the speed control resistors and switch on the return side of the circuit for the motor.
All the above advice is spot on. Start there. I’ll add that if your car sports a cabin air filter, make sure it is clean and passes air freely.