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Weird heater issue

Hey there! I have a 2004 Forester with a seemingly unique climate control problem: As I turn the temp dial from cold to hot, it’s gets to max temp after only a few click. To better explain, if the COLDEST setting is at 9 o’clock, then the HOTTEST setting should be 3 o’clock. In my case, the air is hot by 11, but it won’t get any hotter by 12, 1, etc. (thankfully). It’s as if the entire temp range has been compressed.

Any ideas? Thanks!

That’s not unique to your car. The heater core can’t produce more heat than the temperature of the engine/water. If the max is reached at 9 o’clock than that’s it. The other possibility is a somewhat clogged heater core. An inexpensive back flush could improve and raise the temperature. Search youtube, lots of videos on that topic.

Thanks for the reply! What makes this more interesting is that at 11 o’clock, when my heater is it’s hottest, it’s as if we’re actually at it’s MAX setting. The heater gets plenty hot, just too soon. In terms of radial degrees (NOT temp), the entire 180° range of the dial is compressed to maybe 60°.

When at it’s coldest setting, everything works as it should, a few clicks up and it gets uncomfortably warm. A few more clicks and it’s maxed out and perfect for a frosty morning. It won’t get hotter after that, but I wouldn’t want it to anyway.

Explain that please?


Heater cores are not designed to raise the temperature to not more than around 130 degrees. If the water temperature is ~160-170 at the core it won’t be raised. Give or take a few degrees.


The end result is not much different from what I stated, except I should have said “regulated” instead of “raised”, poor choice of words

The vent control module may be sending an erroneous signal to the blend door actuator causing the blend door to open to soon.


Any time there’s a cooling system anomaly (that includes this situation) I think of air trapped in the cooling system and a possible head gasket leak behind it all - especially with Subarus.