Heater - Always Blows Warm Air

[WoodleySaint]

I've not long bought an Avensis 1.8 VVT, 2001. When I put the heater on minimum, which reads 16 on the dial, it still blows warm air. If I turn it to maximum it still blows the same as when on minimum. I have looked at what I think is the temperature sensor, located in the drivers side lower facia and this is attached.

Does anyone have any ideas what might make this malfunction? Any advice gratefully received.

[gazza1286]

The fault will be with the level/dial mechanism. The flow through the heater matrix is governed mechanically - there is no sensor.

[Q.S.]

The fault will be with the level/dial mechanism. The flow through the heater matrix is governed mechanically - there is no sensor.

Surely it has climate control on this car? If so, there has to be thermostatic control for the heater valve and fan control.

If it didn't have climate control, the temperature dial would be simply hot - cold and no temperature scale.

[WoodleySaint]

The fault will be with the level/dial mechanism. The flow through the heater matrix is governed mechanically - there is no sensor.

Surely it has climate control on this car? If so, there has to be thermostatic control for the heater valve and fan control.

If it didn't have climate control, the temperature dial would be simply hot - cold and no temperature scale.

Thanks for the responses. The temperature control goes from 16 to 28 degrees C and there is a sensor attached to the drivers side facia panel, do you suspect this is faulty?

Thanks again

[Q.S.]

The fault will be with the level/dial mechanism. The flow through the heater matrix is governed mechanically - there is no sensor.

Surely it has climate control on this car? If so, there has to be thermostatic control for the heater valve and fan control.

If it didn't have climate control, the temperature dial would be simply hot - cold and no temperature scale.

Thanks for the responses. The temperature control goes from 16 to 28 degrees C and there is a sensor attached to the drivers side facia panel, do you suspect this is faulty?

Thanks again

If there is an 'auto' on the fan speed dial, it has got climate control. If this is so, does the fan control work correctly in relation to the temperature you have set? If the interior is hot and you set the control to cold ( as far as it goes) the fan should come on full and blow cold air. If this is working correct but the air is blowing out warm, I suspect the sensor is ok.

The problem could lie with whatever mechanism is used to change the temp output of the heater, be this either a valve which switches off the hot water flow or a flap control that directs the airflow either thru or around the heater matrix. (not sure which control type is fitted to these).

If the fan auto control isn't working correctly either, then it could be the sensor or the ecu it connects to.

Sorry it's a bit vague but I don't have a working knowledge of this exact system, going on general heater principles only.

Hope it's of some help.

[WoodleySaint]

Yes, the car has climatic control. I've just done some testing with some inconsistent results:

Temp set to 16

Vent position to 'Feet and Face'

Fan speed on Auto.

With the car stationary and idling the fan started at low speed after a few minutes. After 10 minutes or so the inside temp had increased to 23 (electronic thermometer used).

Put temp to 28 no increase in fan speed

Put temp back to 16 short blip in fan speed, then reverted back to norm... low fan speed blowing warm air.

I then tried disconnecting the temperature sensor, after a few seconds the fan speed increased to max, reconnected and fan speed dropped to low.

Forgot to mention, I have replaced the temp sensor and get the same symptoms so I don't believe that is where the faulty lies.

Does this mean the ecu is faulty? Could I just get one of these from the scrap yard and fit?

[Q.S.]

Yes, the car has climatic control. I've just done some testing with some inconsistent results:

Temp set to 16

Vent position to 'Feet and Face'

Fan speed on Auto.

With the car stationary and idling the fan started at low speed after a few minutes. After 10 minutes or so the inside temp had increased to 23 (electronic thermometer used).

Put temp to 28 no increase in fan speed

Put temp back to 16 short blip in fan speed, then reverted back to norm... low fan speed blowing warm air.

I then tried disconnecting the temperature sensor, after a few seconds the fan speed increased to max, reconnected and fan speed dropped to low.

Forgot to mention, I have replaced the temp sensor and get the same symptoms so I don't believe that is where the faulty lies.

Does this mean the ecu is faulty? Could I just get one of these from the scrap yard and fit?

Certainly seems like the right messages aren't getting through somewhere in the system, could be the climate control ecu or even a faulty connection somewhere in the system.

Sorry I can't be more help, maybe someone else on here has had first hand experience of this problem or similar. Might be a job for Mr T to diagnose with their diagnostic equipment.