'07 IS350 AC Problem
08-10-14, 04:49 PM
#2
Lexus Fanatic
Welcome to CL and CAR CHAT as a new poster. Glad to have you. 
You didn't mention how the other climate-controls were set, except for the A/C itself being turned off. With many (in fact, most) new cars today, compressor-operation is also linked to the windshield defogging. That means that whenever the defrost/defog mode is on, the compressor operates with it as a source of dry, dehumidified (but cold) air for the system to absorb moisture on the inside of the windshield with. Then, if the air-ducts are set into a split-level mode (say, windshield/floor or windshield/dash), some excess cold air from the compressor will also spill out of those vents onto your face or legs. This will often happen even if the A/C compressor switch itself is turned off. The defog/defrost mode, on all Lexus models and on most other new cars, will also automatically switch the intake-air duct from recirculated to fresh outside air to prevent moisture build-up. In fact, when the defog/defrost system is used, it is sometimes beneficial to add a small amount of heat with the temperature (hot/cold) control to prevent chilly air from cooling down the windshield too much and getting condensation on the outside. That will also help the defogging even more by dropping the humidity of the windshield-air as it warms.
So, if this is the case, make sure that when you are using the defrost/defog mode, the dash and floor vents are shut off if you don't want any cold air also escaping through them. There usually is no way to prevent the A/C compressor from coming on with the defrost, except that in some cases (at extremely cold temperatures outside) the system may by-pass the compressor to keep from freezing up.
We also have a specific CL thread, if you prefer, to discuss service/maintenance-related issues.
https://www.clublexus.com/forums/maintenance-11/
You didn't mention how the other climate-controls were set, except for the A/C itself being turned off. With many (in fact, most) new cars today, compressor-operation is also linked to the windshield defogging. That means that whenever the defrost/defog mode is on, the compressor operates with it as a source of dry, dehumidified (but cold) air for the system to absorb moisture on the inside of the windshield with. Then, if the air-ducts are set into a split-level mode (say, windshield/floor or windshield/dash), some excess cold air from the compressor will also spill out of those vents onto your face or legs. This will often happen even if the A/C compressor switch itself is turned off. The defog/defrost mode, on all Lexus models and on most other new cars, will also automatically switch the intake-air duct from recirculated to fresh outside air to prevent moisture build-up. In fact, when the defog/defrost system is used, it is sometimes beneficial to add a small amount of heat with the temperature (hot/cold) control to prevent chilly air from cooling down the windshield too much and getting condensation on the outside. That will also help the defogging even more by dropping the humidity of the windshield-air as it warms.
So, if this is the case, make sure that when you are using the defrost/defog mode, the dash and floor vents are shut off if you don't want any cold air also escaping through them. There usually is no way to prevent the A/C compressor from coming on with the defrost, except that in some cases (at extremely cold temperatures outside) the system may by-pass the compressor to keep from freezing up.
We also have a specific CL thread, if you prefer, to discuss service/maintenance-related issues.
https://www.clublexus.com/forums/maintenance-11/
Last edited by mmarshall; 08-10-14 at 05:00 PM.
08-11-14, 08:49 AM
#4
as long as front defrost is on, either the windshield only or windshield and footwell, the AC is on, whether the A/C button is lit up or not....
drove all winter with defrost and footwell on and got about 12.4 L / 100 km vs 11 L / 100 km the following winter after I figured it out...
drove all winter with defrost and footwell on and got about 12.4 L / 100 km vs 11 L / 100 km the following winter after I figured it out...
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