Heater Runs Hot All The Time

[Chis70]

Hello,

My 1998 3.0 TD Landcruiser prado tx has a problem with the heater. When the car gets warmed up it pumps out hot air, even when the temperature setting is on it's lowest, does anybody know why?

Be very grateful for any help

Cheers

[crofter]

It sounds as if the linkage, which is probably a stiff wire, has either snapped or come adrift from one end or the other.

If I remember right on that model it is a sliding lever to change the setting,Does that seem to have little or no resistance to move ?

Del

[balli hi]

Probably the heater control valve, happened on one of my cars in the past, the valve starts to stick, which in turn causes the control in the cabin to become stiff to turn, eventually the wire slips from its mounting at the valve end......So pretty much what Del has described in his post. hope this helps.

[Chis70]

When I turn the control knob there is no resistance at all. If I leave the knob on it's lowest setting before I start up it will continue to blow cold air but as soon as I turn it up to warm it won't come down in temperature. The aircon isn't working so wondered if that had anything to do with it.

Thanks for your help.

[balli hi]

In basic car heaters, the water heated by the engine normally flows continuously through the heater matrix.

The internal cabin temperature is controlled by shutters/flaps that divert air either over the heater matrix (hot) or direct from outside (cold). - In most modern cars the air usually first passes through an air/pollen filter first, but this does not affect the air temperature.
To obtain warm air, the shutter/flap is positioned to allow some air that has been warmed by the heater matrix and some air that has not, to enter the cabin.

The fault you describe could be caused by the flap/shutter not closing correctly thereby allowing air to be heated and enter the cabin

If the temperature increases when you move the control to hot, then this could be an adjustment issue. If there is no change in temperature, then the controlling linkage (cables) have probably either become detached or snapped.

Does your car have an ambient air sensor ? if it missing or disconnected you will get heat all the time.