heat from vents with AC on!

konakahuna · 03-16-2005, 09:46 PM

here's a weird one..yesterday, i noticed that driving to work in 40 degree rain, there was warm air coming from the vents. checking the temp, i lowered it but without any change. i dropped the temp down to 65..no deal. then i turned on the AC, but no change in temperature. when i dropped it down to MAX COLD, the AC kicked in and very cold air came from the vents.without that setting, the air remains warm regardless of whether the AC button is on or not.

anyone experienced this???

thanks,

david

andyprius · 03-16-2005, 10:21 PM

I experienced something like that, having set the AC to 76 or 78 to conserve fuel yesterday. With a higher setting and more volume it still feels comfortable. However this morning when I drove the car out of the garage it was blowing warmer air, still set at 76-78 from yesterday, however the AC switch was not on (I had not turned it on yet) I think it may be all perception and the fact that in one case the AC was on (afternoon) so the AC is removing humidity, AND in the other case, more humidity was still present and the same 78 setting seemed like warm air. Not ever having experienced anything like this with any other car, it is definitely a new encounter. However I do experience temperature changes with or without the AC, simply by changing settings. Were your two heaters on?

**Tideland Prius** · 03-16-2005, 11:23 PM

With the A/C light on, it doesn't necessarily mean the A/C is running. As andyprius said, it could be dehumidifying the air.

konakahuna · 03-17-2005, 12:01 AM

turning on the AC may not actually do it? my understanding is that AC dries the air. you can have AC with heat, if you want...but in my case, the ambient air was 45 degrees. my AC was on and my temp was dialed down to 65 (the lowest setting before MAX AC) with auto off. and i got warm air.

HTMLSpinnr · 03-17-2005, 12:17 AM

The temperature control is just that - a thermostat. If the air is cold, setting it at 65 could still tell the car that you want heat if the ambient and interior temps are far below that.

Only MAX HOT and MAX COLD actually force full heat and cold respectively.

This is not an conventional old skool car HVAC system. It decides for you :-)

konakahuna · 03-17-2005, 12:22 AM

i think i'm gonna have to reread the HVAC section again. perhaps it is acting normally...but it sure seems strange. at the risk of sounding like a newbie doofus, what if you just want vent?

**Tideland Prius** · 03-17-2005, 12:24 AM

Auto A/C off, MAX COLD (perhaps?), vent, fan speed: LO.

HTMLSpinnr · 03-17-2005, 10:09 AM

Just turn the system off - it opens the "vent" (unless you select recirc) and you will get some airflow at highway speeds due to the positive pressure at the inlet near the base of the windshield.

Tideland's method would work as well if you wanted more forced induction.

konakahuna · 03-17-2005, 11:40 AM

as a postscript to this little tale, toyota of knoxville confirmed this morning that everything is working normally. the defective part, in this case, is the carbon-based prius driver. i went back over the owner's manual and it's a bit vague on the whole "nothing but vent outside air" issue. i think next time i'll try HTML's tip and simply turn the system off and let the air come in through the vent.

thanks everyone for yer help.

d

03-16-2005, 09:46 PM	#1
konakahuna Member Join Date: May 2004 Location: knoxville, tn Posts: 63 My Car: 2005 Prius Model: Package: #5 Thanks: 0 Thanked 4 Times in 2 Posts Friends: 0	heat from vents with AC on! here's a weird one..yesterday, i noticed that driving to work in 40 degree rain, there was warm air coming from the vents. checking the temp, i lowered it but without any change. i dropped the temp down to 65..no deal. then i turned on the AC, but no change in temperature. when i dropped it down to MAX COLD, the AC kicked in and very cold air came from the vents.without that setting, the air remains warm regardless of whether the AC button is on or not. anyone experienced this??? thanks, david

03-17-2005, 12:01 AM	#4
konakahuna Member Join Date: May 2004 Location: knoxville, tn Posts: 63 My Car: 2005 Prius Model: Package: #5 Thanks: 0 Thanked 4 Times in 2 Posts Friends: 0	Re: heat from vents with AC on! turning on the AC may not actually do it? my understanding is that AC dries the air. you can have AC with heat, if you want...but in my case, the ambient air was 45 degrees. my AC was on and my temp was dialed down to 65 (the lowest setting before MAX AC) with auto off. and i got warm air.

03-17-2005, 12:22 AM	#6
konakahuna Member Join Date: May 2004 Location: knoxville, tn Posts: 63 My Car: 2005 Prius Model: Package: #5 Thanks: 0 Thanked 4 Times in 2 Posts Friends: 0	Re: heat from vents with AC on! i think i'm gonna have to reread the HVAC section again. perhaps it is acting normally...but it sure seems strange. at the risk of sounding like a newbie doofus, what if you just want vent?

03-17-2005, 11:40 AM	#9
konakahuna Member Join Date: May 2004 Location: knoxville, tn Posts: 63 My Car: 2005 Prius Model: Package: #5 Thanks: 0 Thanked 4 Times in 2 Posts Friends: 0	Re: heat from vents with AC on! as a postscript to this little tale, toyota of knoxville confirmed this morning that everything is working normally. the defective part, in this case, is the carbon-based prius driver. i went back over the owner's manual and it's a bit vague on the whole "nothing but vent outside air" issue. i think next time i'll try HTML's tip and simply turn the system off and let the air come in through the vent. thanks everyone for yer help. d

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03-16-2005, 10:21 PM	#2
andyprius Senior Member Join Date: Feb 2005 Location: Sacramento, California. Posts: 845 My Car: 2005 Prius Model: Package: #3 Thanks: 12 Thanked 17 Times in 17 Posts Friends: 1	I experienced something like that, having set the AC to 76 or 78 to conserve fuel yesterday. With a higher setting and more volume it still feels comfortable. However this morning when I drove the car out of the garage it was blowing warmer air, still set at 76-78 from yesterday, however the AC switch was not on (I had not turned it on yet) I think it may be all perception and the fact that in one case the AC was on (afternoon) so the AC is removing humidity, AND in the other case, more humidity was still present and the same 78 setting seemed like warm air. Not ever having experienced anything like this with any other car, it is definitely a new encounter. However I do experience temperature changes with or without the AC, simply by changing settings. Were your two heaters on?

03-16-2005, 11:23 PM	#3
Tideland Prius Moderator of the North Join Date: Oct 2004 Location: Canada Posts: 21,204 My Car: 2010 Prius Model: N/A Package: Technology Package (Canada) Thanks: 370 Thanked 529 Times in 356 Posts Friends: 26	With the A/C light on, it doesn't necessarily mean the A/C is running. As andyprius said, it could be dehumidifying the air.

03-17-2005, 12:17 AM	#5
HTMLSpinnr Gen III Forums Moderator Join Date: Dec 2003 Location: Surprise, AZ (Phoenix) Posts: 4,392 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 282 Thanked 516 Times in 246 Posts Friends: 18	The temperature control is just that - a thermostat. If the air is cold, setting it at 65 could still tell the car that you want heat if the ambient and interior temps are far below that. Only MAX HOT and MAX COLD actually force full heat and cold respectively. This is not an conventional old skool car HVAC system. It decides for you :-)

03-17-2005, 12:24 AM	#7
Tideland Prius Moderator of the North Join Date: Oct 2004 Location: Canada Posts: 21,204 My Car: 2010 Prius Model: N/A Package: Technology Package (Canada) Thanks: 370 Thanked 529 Times in 356 Posts Friends: 26	Auto A/C off, MAX COLD (perhaps?), vent, fan speed: LO.

03-17-2005, 10:09 AM	#8
HTMLSpinnr Gen III Forums Moderator Join Date: Dec 2003 Location: Surprise, AZ (Phoenix) Posts: 4,392 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 282 Thanked 516 Times in 246 Posts Friends: 18	Just turn the system off - it opens the "vent" (unless you select recirc) and you will get some airflow at highway speeds due to the positive pressure at the inlet near the base of the windshield. Tideland's method would work as well if you wanted more forced induction.