My heater sucks! But why?!?

So it's getting colder and colder by the day. It wouldn't be so much of a problem if my heater worked worth a damn. But it doesn't. No matter how long I leave it on, whether the engine has been running all day long (not literally, but like I mean even after driving for a bit) or just started up, it will always blow cold-ish air. By cold-ish, I mean not quite as cold as when I have it set to cold, but the air is not even the slightest bit warm. I have swapped out my stock stereo for an Alpine CDA-105 which means I have a dash kit, but I highly doubt that has anything to do with my problem. Anything I could try myself before having to take it in to get the problem fixed?

 

Should probably also include: My 2.5i has manual climate controls.

Does the engine reach operating temp? If you have a thermostat that is either warn out or certain brand new non-OEM ones, they can open too soon and prevent the engine from ever reaching operating temp.

I just went into the dealer for my 60k service and they flushed the coolant system and checked the thermostat. After doing this my heater is much hotter and I have to keep the temp knob one or two clicks cooler than before the service. Maybe a coolant flush would help?

Engine heats up fine. Or at least, according to the gauge it does. Never goes much beyond halfway on the gauge.

A bit more background:

Got the car used with 37k on it. Sitting at just about 43k right now. Only brought it to the dealer once for the ECM reprogramming or whatever it was, and did an oil change myself about 1500 miles ago. That's all the service it's seen so far. But when we brought it in to the dealer (Go Subaru Arapahoe), they did all their little checks and didn't mark anything as needing attention. But that was a little while ago. Idk though. I do need to take it in. It's making an ungodly sound reminiscent of the sound the engine in my Mazda was making after it got oil starved somehow and ended up either needing a rebuild or new engine. We opted for the Legacy instead.

I'm betting it's the thermostat, this is a common thing & a cheap repair. Flatirons Subaru service isn't great IMO, you're much better going to SuperRupair on N Broadway. Still, a thermostat is a simple repair, anyone can do it.

Any other suggestions for Subaru (either exclusively or largely subaru based) repair shops besides that one in Boulder? I don't know that it's worth the like 35 mile drive. I'm out south of Denver at C-470 and I-25. I was thinking Suba Performance if nobody else has suggestions.

Didn't realize you were that far down. Supapros, Roos or Strictly Automotive are all in your neighborhood.

OP, I put in a brand new thermostat 3 weeks ago. Before that I never had problems with heat, but after the new thermostat the heat problem began. The thermostat was either faulty from the box or not a correct replacement (despite the fact that is listed as a correct replacement). Yesterday I put another new thermostat in and the problem is gone.. BUT my engine could not reach operating temp.. and yours does... so I don't know.

Thanks for the suggestions! Now I just need to find time to bring it in.

08 seems a little young for this, but it is possible that the heater core has clogged. It happened in my 05 and it has happened with other 05/06 models here. The theory is that the coolant conditioner will plug up the heater core, starting with the passenger side then reaching the driver's side.

 

It would come on as a gradual loss of heat over many months, so if your problem happened suddenly then I'd be looking at something else.

I don't know if it was sudden or gradual. I got the car in May so I had it for months before I had to bother with the heater so I wouldn't know.

I'm betting on a problem with the blend door or the cable that connects it to the temperature control.

Decided to just take it over to Firestone for now.

I'm with pillboy. OP messed up his HU install

Got the car back from Firestone. They said something just came loose behind the dash, so I probably did screw up the HU install some how. Didn't mess with the cable that much though. Tried once or twice to get it off like the instructions said, and that didn't work so we just took the climate control stuff off from the faceplate like we had to anyways to do it. But either way, it's fixed. Not sure if it was the cable or something else.

 

Side note: Also had an annoying and slightly worrying rattle sound coming from the engine at times. Was really worried that it would be something horrible because I was a bit low on oil last time I did a change. Turned out to just be a loose heat shield of some sort. That's fixed. I do need new tires though.

I'd say it has something to do with your heater core. Your car's 2nd "radiator".

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