heat rarely warms up!

I have a 2005 Subaru legacy with 75k miles on it. My problem is the heat isn't working. Every once in a wile the drivers side vents will work and not the passengers. Sometimes all vents will work. I have tried messing with the settings, and i waited till my car warmed and i still cant find a consistent way to keep it working. Another weird problem is, when the vents are working, when i'm going faster its gets warm and when i slow down its gets cold?? I'm so confused and it sucks not having heat it 15 degree weather. If anyone can give me ideas on what i can do that would be sweet!! Also i recently installed a headunit and i have the manual control HVAC.

First thing, while you installed your new HU, you may have disconnected the manual cable to the heat valve... you should check there first to see if something has been disconnected by mistake.

 

If that's not it, then check your coolant level - it might be low (the engine coolant is what provides heat to the cabin).

 

Lastly, you could have a seized thermostat... if the thermostat remains closed, it won't allow warm coolant to enter the cabin-coolant area... it can also cause your car to overheat.

 

I think it's the first thing, but the others are potential problems as well.

Thank you! The coolant level was very low i hope thats not another problem!

 

Thanks

Is there a certain coolant i need? Brand? thanks again

Buy the green stuff from your dealer. It's expensive, but unless you have a leak you will only have to buy it every 30K miles.

 

No need to pay extra for the blue coolant, since you won't get the full benefits if you just slap it in there. There is a l-o-n-g thread about coolant in the Walkthroughs.

Be sure to fill the coolant into the radiator, not just the reservoir - if it's really low, then it will take a while for the coolant to come through the reservoir properly.

 

And, of course, keep an eye on the level for a little while... you may have a leak somewhere.

 

Lastly, be sure to do this when the engine is cold - don't want you to burn yourself when refilling at the radiator cap.