A couple of times a year, the blower on my 2008 V6 4Runner (w/ 105k miles) fails to run. This is VERY intermittent. Sometimes the blower will spontaneously start running after a few minutes driving, sometimes switching it off then on again will start it, sometimes shutting the engine off then on again starts it, but I am not really convinced any of these steps is actually telling me much (may be just coincidence).

Yesterday it would not run at all, even after fiddling with the switch and stop/starting the ignition. I drove for over an hour with multiple stops and the thing would not blow. I got up this morning to start troubleshooting, and - wouldn't you know it - it started blowing just fine. Multiple on/off/engine restarts etc., it is running just fine every time now.

I live in AZ and it is around 80-90F this time of year, so definitely NOT freezing up, but the blower does run almost all the time. I guess there are three likely suspects: relay, motor connector, motor (brushes etc.). Any suggestions as to which could be causing something so intermittent? I was thinking of eliminating the relay by switching it with the dome light relay (looks the same)... any other ideas?

 

Is it blower motor itself, or the relay? My motor failed and started not spinning up, I just got a replacement used for 35 bucks and was done with it. None of the parts are very expensive

 

Unknown. The problem is intermittent, and never stays long enough for me to confirm if power is reaching the motor. I just switched out the relay, so if the problem goes away then that was it.

 

There is also a blower motor resistor that can go back and cause problems. The blower motor on my 83 could either be completely off or full tilt - nothing in between. Swapped out the resistor and it works fine now. Not sure where one is on your year and model, but on my 83 it was on the driver side with a large square plug going to it. Heat only models have a 3 blade resistor, AC models have a 4 blade resistor.