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

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.

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.

-- Vic Roberts Replace xxx with vdr in e-mail address.

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.

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

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.

-- Vic Roberts Replace xxx with vdr in e-mail address.

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!

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.