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Discussion Starter #1
My heater is acting weird. I was driving on the freeway for almost an hour, consistently at 60 mph or better. The heater is set about mid range (72 degrees on the little zone control dials and mid range on the blue/red dial between the heater vents). Temperature in the car would be comfortable, then it would start to feel quite warm like the temperature dial was set to max.

It didn't sound like the blower motor changed speed, just that the temperature of the air coming out of the vents was a lot warmer.

Coolant (engine) temperature on the dash hadn't changed. Still right in the middle between hot and cold.

I don't notice on my usual commute to work, less than 30 minutes with mixed hwy/city driving. Maybe cause I'm having too much fun running thru the gears or maybe car isn't warmed up for long enough.

I've seen some great posts and how to's on digital CCU but don't see much on the stuff before digital. Any suggestions on where to start?

Thanks in advance guys.
 

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Fireballs inc.
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9,256 Posts
when you go FAST ive noticed the air comming though the vents gets hotter especially when the engine is winding down
 

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BMWCCA HPDE Instructor
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23,464 Posts
How is your coolant level?

I had a similar, but slightly different problem in a previous car; the heat would not get very hot unless I was under acceleration. I found out that the problem was being caused by a slightly low coolant level (radiator looked full, but the side reservoir was empty). There was enough coolant available to keep the engine at normal operating temperature, but not enough to reach the heater core. I topped it off and the problem was fixed. So firstly, I'd check your coolant level just to be sure.

The only other idea I can come up with is that your ventilation flaps which "mix" the hot air from the heater core are not opening/closing correctly. That is not a fun problem to diagnose/fix, since they're all buried behind the dashboard. The flap movement is powered by engine vacuum pressure. Do you hear any unusual hissing inside the cabin with the engine running?
 
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