No heat

[4runnerAzGuy]

I have an 04 v8 4runner and the best just stopped working. I was thinking there was maybe a blockage or air bubble or something I. The header core but I’ve tried to bleed it a few times and pulled the cooling system down to a vacuum and used that to fill and it’s still not working I don’t think that’s the issue anymore.

The lines going to the heater core are hot but from what I read there isn’t a heater core valve anymore. Is the heat controlled just in that whole assembly in the center? I’m not sure what else to check at this point

 

[earshel]

I have an 04 v8 4runner and the best just stopped working. I was thinking there was maybe a blockage or air bubble or something I. The header core but I’ve tried to bleed it a few times and pulled the cooling system down to a vacuum and used that to fill and it’s still not working I don’t think that’s the issue anymore.

The lines going to the heater core are hot but from what I read there isn’t a heater core valve anymore. Is the heat controlled just in that whole assembly in the center? I’m not sure what else to check at this point

The cabin air temp sensor is a pretty common culprit. It's located just south of the ignition, behind the panel. 2 10mm bolts to take the panel off and the sensor is just clipped in to it. Make sure that it's connected and clean. Sometimes the vent for it gets clogged with dust and dirt as well.

 

[AuSeeker]

I have an 04 v8 4runner and the best just stopped working. I was thinking there was maybe a blockage or air bubble or something I. The header core but I’ve tried to bleed it a few times and pulled the cooling system down to a vacuum and used that to fill and it’s still not working I don’t think that’s the issue anymore.

The lines going to the heater core are hot but from what I read there isn’t a heater core valve anymore. Is the heat controlled just in that whole assembly in the center? I’m not sure what else to check at this point

Your problem is most likely the "mode/blend" door actuator/solenoid needs to be replaced or it's become disengaged with the lever/arm on the door, it's a little motor that moves a door that direct the HVAC air either over the AC evaporator or heater core, usually there's a clicking noise from the bad actuator, it's location behind the glove box which has to be removed to get to it and replace it, there are several actuators for the HVAC in the same area, after removing the glove box adjust the air temperature up and down and see which actuator is clicking or trying to move.

There are numerous topics on the forum on "How to" replace the actuators/solenoids.

Also as mentioned the cabin air temperature sensor could be dirty and and not sensing the proper temperature, it's below the ignition switch and behind the little "slots/holes" it wouldn't hurt to check it first by removing it and blowing off any dust on it and see if that help your issue, but be prepared to tackle the solenoid.

 

[4runnerAzGuy]

Your problem is most likely the "mode/blend" door actuator/solenoid needs to be replaced or it's become disengaged with the lever/arm on the door, it's a little motor that moves a door that direct the HVAC air either over the AC evaporator or heater core, usually there's a clicking noise from the bad actuator, it's location behind the glove box which has to be removed to get to it and replace it, there are several actuators for the HVAC in the same area, after removing the glove box adjust the air temperature up and down and see which actuator is clicking or trying to move.

There are numerous topics on the forum on "How to" replace the actuators/solenoids.

Also as mentioned the cabin air temperature sensor could be dirty and and not sensing the proper temperature, it's below the ignition switch and behind the little "slots/holes" it wouldn't hurt to check it first by removing it and blowing off any dust on it and see if that help your issue, but be prepared to tackle the solenoid.

Thanks for the pointers. I’ll check those things out. I’ll give cleaning off the temp sensor a shot first, would it matter even if it was dirty or bad if I’m not on auto. If I’m manually
Adjusting the temp why would it care what the cabin temp is? I’m assuming the individual actuators are replaceable If needed?

 

[AuSeeker]

Thanks for the pointers. I’ll check those things out. I’ll give cleaning off the temp sensor a shot first, would it matter even if it was dirty or bad if I’m not on auto. If I’m manually
Adjusting the temp why would it care what the cabin temp is? I’m assuming the individual actuators are replaceable If needed?

The HVAC system needs to know what the temperature is in the cabin, when you set the temperature manually the HVAC system will output cool, warm or hot air to get the temperature in the cabin to the temperature you have set it at, once it gets to that temperature the system will output air the same temperature as the setting unless it needs to output a different temperature to keep it at that setting.


Yes all of the actuators are replaceable, you just need to make sure you replace the correct one with the correct replacement part.

 

[DamnRandall]

I've got the same issue with mine and after troubleshooting, I've determined that it's an issue with the blend door servo. When you go behind the glove compartment, you'll see two servos on the left side. The top one controls which vents output air, and the bottom one is the blend door servo.

I'm waiting for the replacement part to arrive so I haven't tackled it yet, but I've read that it's a bit of a pain to get the servo out due to an obscured mounting screw. There's a great write-up on the process here: DIY: Replace Servo Sub-Assy

 

[Whamola]

Check your coolant. I had a leak I didn't know about and with it low, it struggled to heat.

 

[4runnerAzGuy]

Ended up being the blend door servo. The cabin temp sensor was filthy too so I’m sure that wasn’t helping anything lol. Changed our the servo though and heat works perfect now, thanks guys

 

[4runnerAzGuy]

I've got the same issue with mine and after troubleshooting, I've determined that it's an issue with the blend door servo. When you go behind the glove compartment, you'll see two servos on the left side. The top one controls which vents output air, and the bottom one is the blend door servo.

I'm waiting for the replacement part to arrive so I haven't tackled it yet, but I've read that it's a bit of a pain to get the servo out due to an obscured mounting screw. There's a great write-up on the process here: DIY: Replace Servo Sub-Assy

Yea one of the screws was a real pain to get too. I ended up printing a stubby little screwdriver bit driver to make it work. Without it I’m not sure how I would have done it