2002 Prius dash hvac controls not working.

Hello Lisa, did you ever find out what the issue was with your controls. I'm having the same issue but the issue started after my AC compressor gave out and my serpentine belt broke and took out the small sensor/connection that is connected to the clutch. I have replaced my AC compressor with OEM Denso and have tested relays and fuses and all are ok. I'm thinking of replacing the AC amplifier but wanted to see if that fixed your issue after the 3rd one.

 

After I first brought my 2003 Gen1 home and got it all reconditioned restored and running as good as it was new, I started looking at amenities, HVAC being part of that. The heat barely got hot and the A/C was all over the place, too cold, too little cold, and the fan was not working right, low worked but auto and the other speeds were come and go. THERE WERE NO TROUBLE LIGHTS OR CODES.

Compressor, Condenser, and refrigerant all were serviced and tested fine. I checked all terminals under the cowling and all terminals were clean and tight, as were all related fuses and relays okay. There is an A/C Fan relay in the main fuse box under the hood that is critical to fan speed operation (**you should check that) That looked like it had been abused by somebody. It tested okay, but I replaced it anyway, but no luck.

Then out of nowhere the fan totally stopped working in every way.

Took the whole center dash panel off to inspect everything else and the circuit boards, as I wanted to replace some dash lights anyway, and wanted to try to repair some major cracks in the panel's plastic. These panels get real brittle with age.

Once in there, I discovered a badly burned and melted foil in the ribbon that connects the main board to the HVAC control board, and when I looked at the 3 control pots for the adjustment knobs, a few of the soldered connector ribbon points were burnt and disconnected on both the temperature control and fan speed control.

This whole center panel from vents to screen opening to HVAC controls is Identified as one part and is called the HVAC center dash panel. I couldn't afford the dealership price for it so I shopped for a good salvaged one, which I found.

It was in perfect cosmetic shaped and everything else looked healthy and clean.

Installed it and everything works as it should, except that the fan only runs at high speed on all settings. For now, I'm okay with that.

Learned that there is a rheostat on the airbox assembly behind the glove box and the center dash, that goes bad if a resistor in it blows and many times it makes it so that the fan only runs on high.

I'll get to it someday when I feel like digging in again, but for now, everything else works great and I'm okay with the fast fan speed.

Bottom line... If the mechanics of your A/C and HVAC test and are okay, save yourself some time by finding a whole good Center Dash HVAC panel, so you don't have to go through all of the discovery time that I spent.

BTW: A lot of people here was telling me that it had to be my condenser, refrigerant, or compressor and/or compressor clutch. I am sure glad that I didn't buy into their expensive "Guesstinosis's".

Hoping that this story gives you some ideas.

 

"Resistor" would be the name, in older cars that used that technology. (A "rheostat" is a resistor whose resistance you can change by physically turning or sliding it, but nobody reaches down to that air duct to twist the blower motor resistor.)

In your Prius, what's there is an electronic circuit board that does pulse-width modulation to control the blower speed. it still has a heat sink and mounts through the air duct to keep it cool, so it's more or less in the same place where an old-timey mechanic would go looking for the "resistor".

 

Yes, I am an "old timey" mechanic, but I have done a good job of keeping up with the times and technology. Been retired for a while now, so I might be a bit less sharp than I once was.
Thank you for the updated info. I still believe that the issue I'm having is most likely in that location. It could also be part of Lisa's trouble, that is why I shared my story.

 

I replaced the AC amplifier on my car and my controls still don't work. I did notice that its not showing the "outside temp" on the LCD display. I also drove the car today and when I drive above 50 the car overheats. Any ideas?