2003 prius no heat

A/C amplifier? Track down the heater hoses which would run from the engine to the firewall. That's going to help find where theheater core is. Now, take the car out and get the engine fully warmed up, feel the heater hoses. Are they warm to the touch. You don't need to have the A/C on for this. If the hoses are warm to the touch, but no heat, you need to install a new heater core. Probably not a bad idea to install a new thermostat, too.

 

The older I get and the faster days seem to pass by, the more I find myself using instruments to get the first information about a problem, before even starting to reach into awkward places and mess with stuff.

Like, use any generic OBD-II reader (if you don't have Techstream) and watch the engine coolant temperature. If it warms up after a bit of driving to within spec (80–84 °C or 176–183 °F for Gen 1) and stays there while the engine's running, the thermostat is fine, and you didn't spend any of your day changing it.

You can find the HVAC check procedure in the manual, same place as the procedure for retrieving codes. It's pretty much the same procedure (fan switch OFF, key ON, A/C button 3 times, fan to AUTO) ... after it does the four 1-second blinks and then blinks you trouble codes if it has any, it is now in Actuator Check mode, and does 5 different things based on where you set the Temp knob (all the way left, 67–72 °F, 73–77 °F, 78–83 °F, all the way right). In each of those five positions, it sets all the actuators a different way (table on page DI-864, 2001 edition).

You can get your head down where you can see the Air Mix and Air Outlet damper linkages (both are visible from down in the driver's footwell) and make sure they both move as expected in all the 5 test positions. (The air outlet position, of course, you can tell just by feeling what outlets the air comes from.) Also, if you see the Air Mix damper really is moving from the full cold to full hot position, and the engine is at operating temperature, pay attention to whether you feel warm air coming out then. If you can get warm air in Actuator Check when you force the damper to hot, but not in normal operation, then the problem might be that in normal operation the amplifier isn't sending it there. Then you might check the inside temperature sensor. (If you have Techstream, you can straight up go to the amplifier data list and read what it thinks the inside temperature is.)

There are some complicated things about the system, but the basic idea of bringing hot liquid into the heater case and blowing air through it isn't very complicated, and if you just keep asking step-by-step questions and finding the answers, it won't be long before you know what's going on. A lot of the information you can find without taking anything apart.

-Chap

 

I had same issue ; 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 ! DK705262 2004-09 TOYOTA PRIUS A/C HEATER SERVO MOTOR ACTUATOR (063800-0240) OEM | eBay
cheap fix ! heater works now

 

One of my 2001 Priuses started blowing heat into the cabin with no regard to the settings of controls. My mechanic discovered that the shaft of the Vane Actuator Motor that controls the direction of airflow through the A/C vent or the Heat Vent had broken so that the vane was staying with the heat direction. I have a 2001 Prius Parts car and want to take the Vane Actuator Motor out to replace the broken one. I am not able to remove the electrical plug from the motor. Does anyone know the secret for disconnecting that plug?

 

You mean this guy?



I don't remember any special secret; I think it was squeeze-the-squeezy-bit and pull, like most of the connectors in the car....

It might be worthwhile to check by hand that the vane moves easily through its full range of motion, before installing a replacement actuator—just in case there was a reason the last one snapped its shaft.

 

I have the problem driving around town it dose not blow heat but if I drive for about 40 miles it will cook u out of the car it gets so hot any ideas on that

 

Hello Cooter - Did you ever figure out the problem? My 2003 started doing the same about a month ago - that is blowing cold, then all of a sudden blowing really hot - today it started blowing nothing but cold - reading old threads by Chapman and others but was wondering if you figured out your issue?

Thanks