Air conditioner blower motor fix.

did you replace the pc board with the fan? what about the switch?

 

Here's a basic drawing and component location diagram. B2, B3, B4. The SI input on the blower motor controller comes from the AC controller. That's located near where A19 is pointing. Most cars default to full speed (only) on the fan when the controller/resistor fails. Perhaps the Prius defaults to slow speed?

 

https://www.autozone.com/cooling-heating-and-climate-control/blower-motor-resistor?filterByKeyWord=blower+motor+controller&fromString=search&isIgnoreVehicle=false&model=motor

Unfortunately, my Autozone link keeps going to their homepage instead of the page I intended. Much cheaper on ebay.

2005 prius blower motor controller | eBay

 

i thought there was a pc board attached to the fan, maybe gen 3? not sure.
so what isn't it doing now? can't change fan speed in manual?

 

There is a controller the fan plugs into. Search for a fan controller

 

It's an electronic speed controller, not attached to the fan, but attached to the duct nearby, so that it sticks into the duct and the airflow keeps it cool.

In the olden days, fan speed would be controlled by a "resistor" (really a little board with two or three resistors, and the fan switch would insert more of them into the circuit for the slower speeds, or shunt around all of them for high speed). The resistors would get hot, so they also used to be mounted to a hole in the fan duct so they were on the inside and the airflow kept them cool.

Because of the similar size and mounting location and (roughly) similar purpose, a lot of people still call the Prius fan speed controller a "resistor".

-Chap

 

thank you!

 

thanks, all the best!

 

The Toyota part number is: 87165-47020 (~$222 list, ~$160 from dealers online)(makes it easier to find on Amazon/eBay),
AutoZone is Part Number: JA1680 (~$150)
I just got one from my local Pick-N-Pull for cheap, still working > 1 year
You want to be careful replacing it, it could have overheated and burned out (most likely), or the fan could have shorted and killed it (in which case replacing it may just burn out the new one.)

Edit: Ha! I just checked the wiring diagram diagnostic for the blower motor (Looking for an ohm value to check the fan for a short) and the official diagnostic is to connect the fan directly to 12v power--if it runs at full speed, it is good, if not, replace. (I was looking for a complicated answer and got a simple Yes/No test. LOL)

 

There are (at least) two ways to slow a DC motor. The resistor method is described above. But since this system uses a dedicated electronic controller module, it's also possible to "chop" the 12 volt supply. In other words, the full current is rapidly turned on and off many times each second. The longer the "off" sequence is, the slower the fan motor will run. This causes less heat and uses less power than simply dumping the excess through a resistor by heating it up. This also typically generates greater strength in the motor, since the brief pulses it sees are still a full 12 volts, rather than a lower voltage and strength that would come from resistors. If you want to learn more, look up PWM or pulse-width modulation. PWM is used for a wide variety of control and signaling uses and is similar to how a lamp dimmer in your home usually works.

The dashboard display shows what the computer is telling the module to do. It has nothing to do with what voltage the module is actually sending to the fan motor. Supplying feedback to the display would make things more complicated and expensive than is necessary.

Therefore, assuming you can reach the wiring, try checking it with a voltmeter on a similar vehicle. I expect you'll find that the voltmeter gives different readings on each vehicle, showing that your controller module needs to be replaced. Since this is likely a ridiculously expensive fix, just go with the full-speed setup you have. Like you said, it's hot there. Also, it's quite possible that the reason the controller module failed is that it got too hot. Be glad it shorted out in the "on" state instead of the "off" state or you wouldn't get any air until you replaced the module. (This is also why you're supposed the check your bathroom's GFI every month. If it fails "on" it won't protect you from getting a shock.)