Cooling fans stopped working

Hi guys:
I own a 2006 Prius with 52k miles on it. Great car BTW. The problem is simple, the radiator cooling fans stopped working on high mode; they run around 25% only even, not removing the heat from the a/c evaporator and the radiator coolant. I checked fuses: OK, checked relays: OK. They spin freely and nothing is blocking the front face of the evaporator. Funny I noticed it when I started hearing the a/c compressor buzzing noise and then I realized the fan noise wasn't there! Uff, its gonna get hot! I had a 88 corolla and the fan motor was the 3 wire type, but this puppy is a two wire type for each motor, thus the power to the motor is regulated and controlled by some kid I have no idea where he is seated.

The thing is that this kind of problem is not detected by the car's computer. Is there any sensor or resistance mounted somewhere that deals with the activation of the fan high speed mode? Thanks!

Fernando

 

Thanks. I'll do my womework and report the results. Have a good one!

 

I checked both relays and were good. The high presssure switch next to the a/c hi port was good. Couldn't find / identify the coolant temp switch, more location hints please!
This is what happened today. I started checking the problem around noon, ambient temp was around 85, the car was parked in the shadow and the engine was cold. I started the car and switched on the a/c on auto at 75, that's usually the temp I set it. Usually, the cooling fans start running on high not more than a couple of seconds after the compressor starts running, they stayed on low running mode. I removed the relays and started checking them starting by the small one, all this while the car was running. Because the removal of this relay turned off the fans, temp started to rise on the condenser, the gas engine was off. Just when I was about to put it back in the socket, a clicking sound (perhaps from the a/c high pressure switch) come sounded along with the right fan running on high. I replaced the relay I had in my hand and then the left one started too, but just for a short period (5 sec) and then "clicked" back to low speed. Well, I thought, the high pressure switch its working, temperature lowered to a safe level and the switch did his job.
Before this whole situation appeared, from inside the cabin, behind the glove box, I could hear, but not a loud noise, what appeared to be a flap or louver sound trying to move or get set usually when the cabin temp was approaching my set temp; usually pressing the recirc button a couple of times (also if outside temp increased, quieted the living dwarf behind the glove box because it stayed "squishing" and was kind of annoying. Right now, there's no effect in pressing the recirc button, when in high fan you could hear the difference between recirc and fresh, not now. Has the servo or the flap gone postal? The thing is all this started simultaneously.

I'm going to check under the dash, behind the glovebox to see what it's going on. Please don't forget to provide me with more a specific location of the engine coolant temp switch. It might not be the cause of the problem, but to be sure and discard it as the cause and check it. Thanks again and sorry for the looong process description. Fernando

 

Ouch! Punctured condenser. Thanks for the expert advice. Seems the a/c charge loss as the primary problem source.

 

Had the a/c condenser replaced and all problems gone, the cabin filter was replaced too. I have to admit, the troubleshooting drill was needed in order to have a better understanding of some functions of my Prius. The leak was very small and slow; but when the pressure dropped below a specified range, the a/c system went postal (and me too! -lol-). Thanks to you guys out there for your expert advice.