Need help with HVAC blower not working

2003 Tacoma with 585K miles

Problem
The HVAC will not blow air at any of the fan speed settings.

Diagnosis so far

• Of all the fuses/relays I can only identify two that may have something to do with this. In the box under the hood, there is a 50 amp fuse labeled "heater" and there is a relay labeled "heater." The 50 amp fuse looks good, and my voltmeter says it has continuity. I have no idea how to test the relay.
• I removed the blower motor and connected the terminals directly to the battery. It spun fast as all get out. It seems the blower motor is OK. There was surprisingly little debris in the blower.
• I replaced the blower motor resistor, since the original one had a fair amount of corrosion, and a new one cost only $15. This did not solve the problem.

What is left?

• Maybe it is a problem with the switch in the control panel?
• Maybe the relay? Can anyone tell me how to test the relay?
• Is there another fuse or component that I am missing?

Look in my signature, and you will see I have plenty of experience with 2nd Gen Tacomas. I think I replaced the blower resistors in all of them at least once, and I replaced the blower motors in two of them. That appears par for the course with 2nd Gens. I can't find much information at all regarding such problems with 1st Gen Tacos. Any help will be appreciated.

 

Looking at the wiring diagram the blower circuit on the 1st gen appears to be set up pretty much identical to the 2nd gen trucks.
Switch grounds the control side (Pin 3) of the HEATER Relay (Powered by the Gauge fuse 10A on the control side (Pin 5) and HEATER Fuse 50A on the load side (Pin 1)) which sends power to the blower motor on the Black/White wire.
Ground to the blower is controlled by the switch, speeds are changed by the switch changing the ground path through the resistor with high bypassing the resistor.
Get you a test light and see if your missing power or ground at the blower motor so we know what part of the circuit to focus on, Black/White should be power and Blue/Black should be ground.

 

Thanks for the quick reply! Earlier today I took my voltmeter back to the truck to get more information. I started by disconnecting the harness from the blower motor and checking the voltage across the terminals. Whaddya know, it was 12V! I plugged it back into the motor, and the motor blows. However, it was noisy, and I'm not sure if it was going full speed. Maybe the connector had gotten cruddy and a few cycles of plug/unplug made for a better connection? I wanted to clean the terminals, but couldn't find anything handy to do the job. Since the motor seems to have issues, and a replacement is not very expensive, I ordered a replacement motor. I would like to get a new female connector as well, but I can't find the right one online. My searches all lead me to 2nd gen connectors. Anyone know where to find the right one?

I am not very skilled in reading wiring diagrams. Am I correct in thinking that voltage at the black/white lead at the motor connector is always 12V when switched on, regardless of fan speed? That is what I observed. To see the change in voltage at different fan speeds I would have to test at a different point in the circuit?

 

Yes the Black/White wire has battery voltage anytime the switch is on, speed is controlled by the switch changing the ground path through the resistor.