1997 Outback Legacy Wagon: Can I get FULL control of the heating/cooling?

[franklin.bowen]

It is hard to believe I have lived with this frustration for 9 years!
So here is my question:
Is it possible to get full control of my heating/cooling system? Right
now there is a relay (or other unknown mechanism) that based on my
choice of ventilation location will sometimes turn on/off either the
recirculation and/or air conditioning. Is it possible to prevent this?
If so, is it easy enough for me to do myself or should I have a
mechanic do it?

PS I used to change my own oil, replace bulbs, check the tire pressure
occasionally, and other minor stuff.

Thanks!

 

[mulder]

It is hard to believe I have lived with this frustration for 9 years!
So here is my question:
Is it possible to get full control of my heating/cooling system? Right
now there is a relay (or other unknown mechanism) that based on my
choice of ventilation location will sometimes turn on/off either the
recirculation and/or air conditioning. Is it possible to prevent this?
If so, is it easy enough for me to do myself or should I have a
mechanic do it?

PS I used to change my own oil, replace bulbs, check the tire pressure
occasionally, and other minor stuff.

Thanks!

I don't know about your car specifically, but on the late model
Imprezas with manual HVAC, there is a microswitch attached to the mode
control that automatically turns on the AC compressor in defrost mode.
It's a simple matter to disable that switch to give you full manual
control over the compressor and allow for defosting with airflow only
and no AC. Perhaps the arrangement on your Legacy is similar.
As for the recirculation, I am not aware of any automatic control that
does this.

 

[Victor Roberts]

It is hard to believe I have lived with this frustration for 9 years!
So here is my question:
Is it possible to get full control of my heating/cooling system? Right
now there is a relay (or other unknown mechanism) that based on my
choice of ventilation location will sometimes turn on/off either the
recirculation and/or air conditioning. Is it possible to prevent this?

I have a 97 Outback wagon that I have driven for over
112,000 miles and don't believe I understand your problem.
The only time the AC goes on "by itself' is when the air
control is set to windshield defrost and the outside air
temperature is high enough. This is by design. Of course,
when using the AC the compressor will cycle on and off as
the frost sensor detects ice buildup on the evaporator.

I can't think of any time when the recirculation would go on
by itself.

 

[Garry]

Franklin,
I have a 96 Outback and can feel your pain; two issues I have with the HVAC
system:
1. When you put it in defrost mode, it turns off the Recirculate feature.
Usually, this is correct, but is annoying if you are running the
defroster
in order to melt ice off of the windshield on a cold morning. In
such cases,
you don't want to suck more cold outside air into the vehicle.
Also, when driving through construction dust, smoke or I spot a dead
skunk ahead;
when I press the recirculate button, I want it to recirculate! As it
is, I also have to
press an additional button to get it off of defrost before it will go
into recirculate.
2. As others have noted, when you put it on defrost it cuts on the AC.
Again, this is usually correct. It does occasionally cause a problem
here in humid North Carolina.
On muggy summer nights, the defrost cools the windshield enough to
cause considerable condensation
on the outside. I have learned to mitigate this by also turning up
the temp slider, but I would like to be able
to turn off the AC and still run the defrost.
But before I get deep in this, I need to install the 2.2L engine I bought
from a Japanese recycler.
I'll let you know what I find out.
Garry

 

[Michael Pardee]

Franklin,
I have a 96 Outback and can feel your pain; two issues I have with the
HVAC
system:
1. When you put it in defrost mode, it turns off the Recirculate feature.
Usually, this is correct, but is annoying if you are running the
defroster
in order to melt ice off of the windshield on a cold morning. In
such cases,
you don't want to suck more cold outside air into the vehicle.
Also, when driving through construction dust, smoke or I spot a dead
skunk ahead;
when I press the recirculate button, I want it to recirculate! As
it
is, I also have to
press an additional button to get it off of defrost before it will
go
into recirculate.

That is pretty standard, but I agree with you that it can be a problem. The
ice issue is not a biggie, since scrapers and deicer sprays work well (I
don't like the sprays with glycol, though - they tend to be messy). But it
is kind of inconvenient to have to turn the ventilation off when going
through various pollutions.

2. As others have noted, when you put it on defrost it cuts on the AC.
Again, this is usually correct. It does occasionally cause a problem
here in humid North Carolina.
On muggy summer nights, the defrost cools the windshield enough to
cause considerable condensation
on the outside. I have learned to mitigate this by also turning up
the temp slider, but I would like to be able
to turn off the AC and still run the defrost.
But before I get deep in this, I need to install the 2.2L engine I bought
from a Japanese recycler.
I'll let you know what I find out.
Garry

It would be nice if the defrosters could have a little more intelligence.
Again this behavior is pretty standard. The design is meant to dehumidify
the air being blown against the windshield. Technically, the system would
have to know the temperature of the windshield to determine how close the
air temperature was to the dew point of the windshield. I think as a
practical matter the windshield could be assumed to be about the same as the
outside temperature and the decision to cool and dry the air could be based
on that.

The '85 Volvo I have doesn't even have a provision for recirculate (it
recirculates if the temperature control results in full heat or full
cooling), so some control is better than none!

Mike

 

[Victor Roberts]

That is pretty standard, but I agree with you that it can be a problem. The
ice issue is not a biggie, since scrapers and deicer sprays work well (I
don't like the sprays with glycol, though - they tend to be messy). But it
is kind of inconvenient to have to turn the ventilation off when going
through various pollutions.

It would be nice if the defrosters could have a little more intelligence.
Again this behavior is pretty standard. The design is meant to dehumidify
the air being blown against the windshield. Technically, the system would
have to know the temperature of the windshield to determine how close the
air temperature was to the dew point of the windshield. I think as a
practical matter the windshield could be assumed to be about the same as the
outside temperature and the decision to cool and dry the air could be based
on that.

In order for the system to know the dew point on the outside
of the car it would need both a temperature sensor and a
humidity sensor - something it does not have. When the
humidity is high enough to cause condensation on the outside
of the windshield, then you usually DO want dehumidified air
blowing on the inside to help get rid of the interior
condensation. It's a simple matter to add a bit of heat to
raise the temperature of the air being blown on the inside
of the windshield and avoid condensation on the outside. And
then you get dry, hot air on the inside which is even more
effective at removing condensation than dry cold air.

 

[franklin.bowen]

Thanks for the replies/discussion. Yes, I am referring to the A/C and
recirculate controls (sometimes) automagically changing if I set the
ventilation to defrost or defrost & feet. I want to turn off this
feature. I will pull out my Subaru book and see if I can figure out
how to "turn it off". If anyone knows, please post. If I figure it
out, I will post.

Thanks!

 

[franklin.bowen]

Yes, I am referring to the A/C and
recirculate controls (sometimes) automagically changing if I set the
ventilation to defrost or defrost & feet. I want to turn off this
feature. If I figure it out, I will post.

Thanks!

I finally took the time to look at this but have not yet found a
solution. I think the device I want to disable is the Evaporation
Thermo Switch (ETS). I removed the glove compartment and the cover
back panel to get access to the ETS and just unplugged it but then it
seems that my A/C did not work at all and the recirc would turn off
when I put the mode in defrost. NOT what I wanted.

Does anyone know if it is safe for the car if I just try shorting
different paths on this connecter or whether I can even achieve what I
want with the ETS connecter? Any other ideas would be greatly
appreciated too.

Thanks!

 

[mulder]

I finally took the time to look at this but have not yet found a
solution. I think the device I want to disable is the Evaporation
Thermo Switch (ETS). I removed the glove compartment and the cover
back panel to get access to the ETS and just unplugged it but then it
seems that my A/C did not work at all and the recirc would turn off
when I put the mode in defrost. NOT what I wanted.

Does anyone know if it is safe for the car if I just try shorting
different paths on this connecter or whether I can even achieve what I
want with the ETS connecter? Any other ideas would be greatly
appreciated too.

Thanks!

If that's the sensor that's in the evaporator, it is what determines
when the compressor should cycle on and off. If you disable it in any
way the AC will no longer work. I'd leave that alone.