It's cooling just fine, but the heat is very weak and fades almost immediately (rendering the air temperature to ambient).
If I wait long enough before starting the fan, the heat is strong at start, but then fades away after a few seconds.
What I've tried
- Checked the heating unit hoses that come from the main radiator - they are both hot, so the water system is not clogged
- Checked the air temperature switch (one of those knobs you turn from blue to red - cold to hot) - it pulls a green cable that goes to a black box under the dashboard, to the right of the gas pedal. I think this box contains a fan as it started humming when I turned the fan on. So cable is fine.
So everything seems to be in place, but it's still not heating very well. I have one theory - the green cable that shifts between the hot/cold units is working fine - but something is wrong in the 'hot area' system - maybe something is blocking the air from passing through the heating unit, and instead the air is sucked from other places, i.e, holes etc?
ideas on how to proceed with this?
EDIT
Car type is Daihatsu Sirion CZ 2001
