LHMARK From United States of America, joined Jan 2000, 7255 posts, RR: 45 Posted (8 years 5 months 5 days 20 hours ago) and read 1365 times:
Confession time. In all my 35 years, I have never properly figured out how to use the defroster setting on my car's heater. All too often, I add the wrong mix of hot or cold, and the window goes opaque with condensation.
Can anyone enlighten me about when to add hot, or when to use cold, to keep the windshield clear?
"Sympathy is something that shouldn't be bestowed on the Yankees. Apparently it angers them." - Bob Feller
TZ757300 From United States of America, joined Aug 2005, 2885 posts, RR: 6
Reply 1, posted (8 years 5 months 5 days 18 hours ago) and read 1360 times:
Well, during the summer, if you have condensation on the inside, just run the air conditioner to run out of the defroster vents. The A/C will take out the moisture from the car and the condensation will go away.
During the winter though, it depends on how cold it is. If its super cold, just run the hottest it can for awhile and it will go away eventually. Say if its like 40-50F, run the coldest air you can get on it. The inside air temp will match the outside air temp and the condensation should go away. Well, at least it works for me
CastleIsland From , joined Dec 1969, posts, RR:
Reply 2, posted (8 years 5 months 5 days 18 hours ago) and read 1354 times:
Many cars these days have a setting whereby if you set the air direction to defrost, the air conditioning automatically comes on. Other than removing true frost from the windshield, where heat is needed, condensation from breath is best removed by cold air, because it is drier than warm air.
My question is, if the AC automatically comes on in defrost mode, what happens if I have my heat settings on 72 degrees? Am I stressing my AC?
Queso From , joined Dec 1969, posts, RR:
Reply 3, posted (8 years 5 months 5 days 17 hours ago) and read 1348 times:
Quoting CastleIsland (Reply 2): My question is, if the AC automatically comes on in defrost mode, what happens if I have my heat settings on 72 degrees? Am I stressing my AC?
It's no problem. The air handling system in most cars directs the air through the A/C evaporator first, then it goes through the heater core where it will be warmed back up to the temp you select.
Of course, when it goes through the evaporator it dumps some heat energy into the refrigerant (depending on the temp of the air going through the evap) to be dissipated through the condensor but it's no where near the heat transfer it would have to do on a 110 degree day.
It's slightly inefficient when the weather is cold, but it works well.
CastleIsland From , joined Dec 1969, posts, RR:
Reply 4, posted (8 years 5 months 5 days 17 hours ago) and read 1335 times:
Quoting Queso (Reply 3): It's no problem. The air handling system in most cars directs the air through the A/C evaporator first, then it goes through the heater core where it will be warmed back up to the temp you select.
Bushpilot From South Africa, joined Jul 2007, 0 posts, RR: 1
Reply 5, posted (8 years 5 months 5 days 15 hours ago) and read 1300 times:
Confession from me, being a life long Alaskan, I thought the defroster was actually for getting rid of frost. I am talking about the half inch of it built up on the windshield when you go out to start your car in the morning and let it run for 20 minutes to heat up. Full blast power and as hot as you can get it, is the only way I have ever run it. When it gets to warm shut it down, or open a window. Most folks I know up here on older cars with actual A/C in it, just cut the belt for AC. Dont need it, and when gas is running 4.61 a gallon, every little bit helps. Also keep in mind I live in the middle of nowhere and all of our shit is jerry rigged to the utmost.
Go3Team From United States of America, joined Mar 2004, 3268 posts, RR: 15
Reply 6, posted (8 years 5 months 5 days 9 hours ago) and read 1251 times:
It usually doesn't matter what temperature it is, as long as you are comfortable. The a/c won't overpower the heater, but dries the air enough to take the moisture built up on the inside of the windshield. The outside is another matter. I've cracked 4 windshields trying to remove a layer of ice with the defroster. It's a good thing it's not my vehicle...
GuitrThree From United States of America, joined Oct 2004, 2063 posts, RR: 8
Reply 7, posted (8 years 5 months 3 days 11 hours ago) and read 1200 times:
Whatever you do, if your car allows it, do NOT run the defroster with the air circulation switch to "recirculate." A lot of cars will not provision for this arrangement, but I've seen some, especially Japanese ones, which let you turn on the Defroster and Select Recirculate. When you don't let the air escape, and/or bring in fresh air, the windows will fog up (condensation) even with the Def on. This is true even when it's raining out. A Toyota Dealer told me that the Camry I was driving did that because of the difference in moisture levels inside and outside the car. He said it was a major complaint with the cars, even though there was nothing wrong with it. Even in the Owners Manual, it tells you the proper use. The car was a late 90's model, and I'm not sure if they made the correction to not allow you to do this anymore. I know when I switch my Buick's Automatic HVAC unit to Defroster, it locks out the Recirc button.