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Old 04-27-2008, 05:11 PM   #1 (permalink)
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Default outside air cool, inside air hot

Hi everyone,

I just got my 06 outback 2.5 a few months ago and I love it. There's one thing I can't figure out though. I'm getting warm air coming in from the air vents when I just have the fan on and when the outside air temperature is cool. I've been told by the dealer that it is the heat off of the engine and is normal. javascript:smilie('')
frown I never noticed this on other cars I've owned. I don't think I should need to use the AC even when the outside temperature is cool. This doesn't make any sense. If the outside air is cool, than I should be able to get cool air blowing into the car too. Anybody having similar issues or is this a normal thing?

Andy
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Old 04-27-2008, 06:24 PM   #2 (permalink)
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Default Sounds a bit strange

I have an 05 and don't see this happening in conditions you've described.

Obvious questions:
  • Is the temp control turned all the way to the blue dot? (Assuming manual HVAC controls here.)
  • Is the recirculate button on?
  • Are all the vents open?
  • Is it alleviated at all by increasing the fan speed?
  • Has it always done this or is this the first time?
  • Any recent work done on the car?
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Old 04-27-2008, 06:39 PM   #3 (permalink)
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Thanks for the reply wbanas.

It seems to have always done this. The temperature is all the way to the blue dot. The recirc button is off so you'd get outside air. All vents are open. I recently had the cabin air filter replaced which was absolutely filthy since I also noticed a bit of a musty smell coming from the AC. It helped a bit as far as the smell but I also had the dealer run an air deodorizer through the evaporator just yesterday and I'm waiting to see how much that helps as far as the smell is concerned. It seems a bit better so far. But back to the more pressing issue, the fan blowing warm air when the outside air is cool stills boggles me. Looking forward to any other thoughts.
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Old 04-28-2008, 08:52 AM   #4 (permalink)
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There shouldn’t be a significant increase in temperature, although I have noticed that after the car is parked in the sun, it will blow warmed air, probably because the metal around the intake area (just below the windshield) and the air in the interior space itself is hot. But this dissipates fairly quickly. In normal driving, the incoming air should be almost as cool as it is outside. (Hot coolant is always circulating through the heater core, so there will be some heat generated inside the heater housing. However, this should be minimal, and yes, if it is cool outside you should be able to cool the interior without using the A/C.)

A quick guess would be that the linkage from the temperature control to the heater is either loose or misadjusted.

Assuming that your HVAC control is manual (not automatic), then it’s a fairly simple system. The front panel temperature knob is connected by a cable (fixed outer housing, moving inner core) to a lever linkage arrangement on the driver side of the heater housing. When the control is turned, the inner part of the cable moves the first lever which then moves the next which in turn moves a “door” inside the heater housing that adjusts the path of the air, i.e., through the heater core (which is always hot), partially bypass the core (i.e., mixing some warmed air with cool air), or totally bypass the core (when the control is at the blue end). The outside housing of the cable is clamped to the side of the heater box and should not move when the control is adjusted.

Possible problems:

If the cable is not firmly attached to the heater housing, then as the control is moved, the cable itself can move instead of the lever/door being moved.

The cable might be tightly clamped, but in the wrong position. In this case, even when the temperature control is in the full cold position, the air temperature door inside might not be. Question -- can the control be moved to the full hot position (red dot) without forcing? If not, then this could indicate maladjustment.

Finally, I recall reading elsewhere where the lever linkage itself has become disconnected, resulting in no control of the temperature.

On my '07, the action of the lever system is visible through an opening in the lower cover of the instrument panel just above the accelerator pedal. When the temperature control is in the full cold position, a white lever that the cable is connected to appears to be just above horizontal, pointing towards the front of the car (in other words, in the 10:00 o’clock position). When in the full hot setting, the white lever is down, at about the 7:00 o’clock position.

In order to see more, including the clamp, the bottom cover of the instrument panel would have to be removed.
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Old 04-28-2008, 01:49 PM   #5 (permalink)
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Thanks Plain OM. That is such a thorough explanation of what might be the problem. I'll check all that out and get back. I did notice this morning that I didn't have this problem since the car sat overnight and it wasn't hot in the morning. So it might actually be a thing where when it sits in the sun all day and then takes a while to cool down.
I've mainly noticed this happening at the end of the day when I head home from work. The car sits in the sun, I drive it home using the AC and when I get to my daughter's school, I shut the AC off, go pick her up, get back in the car to head home. By that time though it's later in the day and the outside temp is cool. So then I try just using the outside air only with no AC and out blows warm air. I think you might be on to the right thing with the heater doors though. I'll really check it out thoroughly. Thanks again!
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Old 04-30-2008, 09:03 PM   #6 (permalink)
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Drove the car today to Disneyland and everything seemed okay. Outside air was fairly cool and the inside was too. I checked the heater doors and they seem okay. I think it must just be a thing where the car sits in the hot sun all day and takes quite a while to cool down. I also parked in the parking structure at Disney and had no problems on the ride home. Simple solution. Thanks for the help. I'll keep you posted if anything else changes.
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Old 05-12-2008, 03:31 PM   #7 (permalink)
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Default still can't figure this out

still can't figure this out

Hi all,

I'm still trying to figure this issue out with the ventilation system. Let me run this past you if I may.
I drove the car to dinner and the outside temp was 65. The air blowing in from the vents was a little warm. I park and go have dinner for at least an hour. I get back in the car to drive home. Outside temp is 64, the air coming in from the vents is much, much warmer. The engine should have cooled down by then so I don't think it could be heat from that. What the **** is going on? The air stayed warm all the way home which took ten minutes. I did check the door to the heater vent and it seems like it's closing all the way but can't tell for sure. Maybe I should have the dealer really take a good look at it. Any help would be greatly appreciated.

Thanks again.
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Old 05-13-2008, 01:32 PM   #8 (permalink)
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That may not be that unexpected.

During the hour long cool down, heat was rising off the engine and warming up the air intake area at the base of the windshield and the firewall.

Then you started drawing air thru this heated plenum structure.

Were you running the fan on high? Higher air velocities would likely raise the air temp less, and also cool the plenum off faster.

Was your drive home in slow city traffic or at highway speeds? Higher speeds would increase the percentage of cooler outside air coming in vs the warmer air that collects off the warm engine and comes up to the air intake area.

10 minutes isn't a lot of time, if the air flow was low, to cool things down.

On my automatic climate control system, I frequently get the AC coming on shortly after startup, even when the outside temps wouldn't seem to warrant the AC running. But then within 10 minutes or so, it goes off again after things cool down.

Try running the fan faster after you first start up, and maybe crack a window open too, to help with airflow thru the car.

Also, try running the fan in the recirculate mode, and see if that air is warmer or cooler than outside air. If the outside air is warmer, then it's drawing in the warm air. If the recirc air is warmer, then you are somehow heating the air--either from residual heat or from the heater core.
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Old 05-13-2008, 02:57 PM   #9 (permalink)
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Thanks Wilsonhp. It sounds like it could just be a normal thing with this car. It was all city driving coming back from the restaurant. The dealer also said that it is just warm air coming from the engine compartment and is all normal. The last car I had didn't have that issue and it's just something that I'll need to get used to. I also wonder if it has something to do with the fact that Subaru engines run a bit hotter in general than other engines which in turn would cause this issue. Awesome car though. Wouldn't trade it for anything.
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Old 05-15-2008, 05:13 PM   #10 (permalink)
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Default A more objective approach to the air temperature measurement

Despite my belief that the temperature of the air coming out of the vents with the temperature control set to cold is the same as the outside air, andy g’s observations made me try a more objective approach. It seems to confirm his claim, at least to a degree.

I taped a small, 1-1/2 inch round, mechanical dial thermometer over the center left vent (lots of room for air to go out around the meter) and measured the air temperature on two trips. In summary, after the car had been driven for about 15 minutes and the engine was fully warmed up, the air exhausting from the vent (incoming air directed to the upper vents and the fan on position #3) was at least 5 C higher (approx 10 F) than the outside air temperature.

In some respects, the result was not unexpected having looked at a diagram of the heater box. The heater box contains the heater core, which is a small radiator that is in the coolant circulation path and therefore is as hot as the coolant. Even with the heater set to cold, which places a small door in the air path so that it should bypass the core, the air in the heater box around the core will heat up considerably, and that air will mix with the bypass air, thereby warming it.

The measurements seem to confirm, at least in a preliminary manner, that the air coming out of the vents could well be warmer than the air outside even with the heater control at “cold”. Just how much different would require more exacting measurements and would benefit from others trying the same experiment to see if it is common.
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