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2010 Forester only blowing heat on driver's side - any ideas?


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I noticed the other day that my 2010 Forester is only putting out heat on the driver's side, and cold air on the passenger side.  It doesn't matter what setting I use for the heater, it only blows cold air out the floor, defroster, or dash on the passenger side.  The driver's side seems to work fine though.  I'm guessing maybe it's a broken vacuum line under the dash somewhere, assuming vacuum is what controls the heater settings.  Any ideas where I should start looking?  

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It's only single zone climate correct? Meaning, the driver and passenger cannot have different temperature settings?

If so, it can't be a actuator as you have heat on the drivers side, just not on the passenger side. The actuator is working if you have heat on the drivers side.

2 possible issues. There is air in the heater core, or the heater core is restricted. 

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Yes, it's single zone climate.

By air in the heater core I'm guessing you mean air in the cooling system, and I need to bleed it out?  Even if there was air in the heater core, why would it just blow heat on one side?  It seems like the whole system would be cold.  I'm not being a jerk, I'm just trying to understand.  Thanks!

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Yes, air in the cooling system. The heater core is typically the highest point or very closely to it (stupidly enough) on most subarus, and therefore any air in the system collects in the heater core.

In my experience, typically a lack of heat only on the passenger size indicates a restricted core, but an air pocket in just the right side of the heater core could have the same symptoms. 

 

To see if there's air in the system, warm the car up. Once it's warm, while stopped in park, floor the gas pedal so the RPMs rapidly go up to about 3.5k or so. Then let it come back to an idle. Repeat until heat improves.  This will indicate there's air in the system.

To tell if it's a restricted core, just hold the RPMs up to like 3.5k steady in park. See if heat returns on the passenger side.

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If I have a restricted core, do I need to flush it out to get it working again?

Another thought:  I just had the timing belt and water pump replaced.  I'm thinking maybe my mechanic didn't get all the air bled out of the system?  Sounds like maybe I should start there?

Thanks for the info guys!

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  • 1 year later...

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