2003 Prius--no heat on drivers side ?????

What you are thinking does sound possible to me. If you get the codes from the heat/ac computer, they might even tell you if one of the damper servos isn't responding correctly.

To get the codes: 1. turn ignition to OFF and fan switch to OFF. 2. Turn ignition to ON (only ON) and within 5 seconds tap the A/C button three times and then turn the fan switch to AUTO.

If you got the timing right, the LEDs in all four heat/AC controll buttons will flash slowly four times, and then the one in the A/C button will start blinking codes. If it is just a steady fast blink then there are no codes to help figure out the issue. Otherwise it will blink two-digit numbers for you, as in "blink blink (pause) blink blink blink (longer pause) blink blink (pause) blink blink blink blink" would be 23 and 24.

If you get any codes post them back here.

Finally figuring out the problem, especially if there are no codes to help, might call for the diagrams in the New Car Features manual and the service manual, which you can view online on techinfo.toyota.com for a pretty cheap fee that allows a day or two of access.

-Chap

 

21 is the solar sensor, usually due to lack of direct sunlight. Were you doing this test indoors or in the shade?

 

Hello to knowledgeable mechanics & learned folks !

I bought a 2003 Prius last yr, the car runs very smooth, no noises or any check engine lights ,A/c works too .The heater blower however comes on and blows air, the air doesn't get warm -just blows cold air ,forever !
There are no codes read when I took it to Autozone/AA parts , where they used an advanced scanner . I tried the above method of AC blink codes , but after several attempts , there are no codes displayed - no blinking of any ac led's .. what should I be doing now?

I bought it cheap & cant invest more into it. The coolant levels are near to max & was last replaced about 30k miles per carfax & am not sure if seller changed it before selling, the prestone antifreeze gauge shows good antifreeze readings. I have bought Zerex asian car anti-freeze to replace coolant.

Appreciate all your time & inputs . Thanks !

 

The way the HVAC code check works: once you request it as described above, the button lights flash slowly four times, then one of two things will happen. (1) if there are no diagnostic codes, the A/C light will just blink a steady rapid twice a second. Or (2), if there are codes, it will blink those out slowly, one digit at a time.

If you are saying that none of that happens (no four slow blinks, no A/C light blinking at all), then there are only two possible explanations: (1) you're somehow not getting the procedure quite right, or (2) the HVAC electronics are either not getting power, or completely failed in such a way that they can't even give you codes.

So, I'd try again extra carefully just to rule out (1), and if that's ruled out, you'll have to track down and fix whatever the trouble is with the controls: sign yourself up at techinfo.toyota.com, pull up the repair manual and the wiring diagram, and start narrowing down possibilities.

-Chap

 

Chap, You were right! I hadn't got that timing right, to get codes. After several attempts I got ac codes as 21 . Other members have written about code 21 as solar sensor etc ..my car shows outside temperature on LCD screen correctly as per temperature. What should be my next course of action?
I am signing up for the Toyota site u mentioned btw

Thanks again

 

Hmm, if the only code was 21, it doesn't tell you very much. Probably you were in the dark when you pulled the codes, right? There will always be a code 21 any time there isn't strong light shining on the sensor. But you have successfully ruled out some of the possibilities, like completely dead controls or lost power. The controls are awake enough to respond to your code request. Knowing that is progress.

Now that you know you can get that far, you can also do the "actuator check" that's on the next page in the manual, right after the DTC check you just did. Basically, as long as you leave the system in that DTC blinking mode, it also changes the meaning of the center, "temperature" dial. It gets split into five ranges, and as to move it through those five, all the dampers should move around to specific positions and the fan goes to specific speeds, as shown in the table on that page (it's page DI-864 in my printed copy of the 2001 manual; once you are signed up online, I don't know if the page numbering will exactly match, but you shouldn't have trouble finding it).

That might be an easy way to catch if one of the damper servo motors isn't doing what it ought, or something else might be going on.

-Chap

 

I did check in good day light & still getting only code 21. The "actuator check" is also a pass according to me as the fan changes to specific speeds when temperature dial is moved across . Will keep you posted after I rule out some more possibilities ..or you can suggest as well . Thanks !

 

That actuator check mode isn't just a check of the fan speeds, though. It puts all the actuators of the heater through their paces so you can confirm they all work. That is, with the knob all the way to the left, you should have the fan at a low speed, the air mix damper all the way to cool, the inlet damper all the way to recirculate, the outlet damper in the face-vent position, and the compressor clutch pulled in. With the knob all the way to the right, you should have the fan at highest speed, air mix moved fully to warm, inlet moved fully to fresh, outlet moved to foot+defrost, and compressor clutch released. And so on for the in-between positions, as shown in the chart on p. DI-864.

So to declare your actuator check a "pass", you really kind of have to stick your head down there and watch those things.

-Chap

 

Thanks Chapman & all others ! I suffered in the cold last year but this year I was determined to solve it; did a coolant/antifreeze flush but after doing more research with inputs from all senior members here ,found out that the low humming noise from below the steering wheel was from the AC blend actuator/servo motor ! I manually pulled down the latch & heater worked ! later bought replacement part
DK705262 2004-09 TOYOTA PRIUS A/C HEATER SERVO MOTOR ACTUATOR (063800-0240) OEM | eBay
lucky it was a cheap fix !