Thread: Heat always on (405 MI16 1990)

Hi! this is my first post.

I have a problem that is kind of irritating now when the summer is closing in.
The ventilation is always blowing full heat :?
When I turn the engine on (it's cold) and have the fan speed set to zero no air comes out of the vent. But when the heat builds up in the engine more and more air is coming out. And when the engine is on full working temp (~80C) the vent is blowing with full power and full heat (really hot!) even if I have the fan speed set to zero (blows even more if I turn it on).
Turning the temp control makes no difference at all. I have checked that the control generate different resistance(ohm) when turned.

Some months ago I removed the black box behind the radio, I thought it had something with the alarm (that doesn't work) to do.
When this problem with the head started (I'm not 100% sure if it was at the same time as the removal of the box) I first didn't think about that box, but later when I followed the cables from the heat control I realized that they ended in a connector. So I searched for the box and read the text on it, it said thermal something, god I was embarrassed :?
I reattached the box and thought I would live happily ever after, but NAH! the box didn't fix the problem at all.

Has anyone had the same problem? My guess is that the box is either broken or something gets confused when it's reattached. Or maybe the engine that controls the cooling water flow is jammed at fully open.

Please help.
Best regards Linus.

Sounds like the valve which controles the flow of your heater is malfunctioning (not closing).
Try http://forum.405mi15.com

I have been searching for a bit but not sure where it is.
Where can I find this valve?

sounds like exactly what he said ^^ :lol: trip to a breakers yard for you i think