Is the Air Conditioner supposed to "automatically" kick on when you turn the air vent selector to defrost?:confused: I know the air conditioner helps with the "defrosting" but sometimes I want "heat" selected in the defrost mode and then it seems I'm running the A/C at the same time heat is coming out. My A/C light doesnt actually come "on" when I turn it to defrost but I know it automatically kicks on because my RPMs go up and colder air comes out. What Gives???:confused:

Normal

I dont remember any of my previous cars doing that. Previous cars would just take it off of "recirculating air" and just blow the outside air and if I needed extra defrost then I would be the one to select the A/C NOT THE COMPUTER. That sucks for the very reason that sometimes I turn it to defrost with the heater on then I got the A/C competing with the heater which is why I think previous cars didnt have that design. :mad:

there a fix to that issue. You can disconnect the wires to eliminate that A/C acvtivation when you use the defroster.

There's a way to disable this feature. Check out 'Lon's Garage' for the easy 'How to...'

Is the fix in the members section? What about a fix for disconnecting that annoying buzzer when you first start the truck - BEEP BEEP BEEP BEEP BEEP (Its like enough already the truck is started, seat belt on and I'm out of the driveway and your still beeping at me - GEEEESH!):cry: :cry: :cry: (I guess I feel like whining today.:D :D :D

Originally posted by puppychop3
Is the fix in the members section? What about a fix for disconnecting that annoying buzzer when you first start the truck - BEEP BEEP BEEP BEEP BEEP (Its like enough already the truck is started, seat belt on and I'm out of the driveway and your still beeping at me - GEEEESH!):cry: :cry: :cry: (I guess I feel like whining today.:D :D :D

PC,

These mods are in Lons' Garage sectoin, you as a club member have full access to these areas, use the search feature to find them (its faster than trying to hunt up and down the lists of forums and threads to get to these) then click on them from the search results and scan away for your solutions. If you still are having trouble, I'll help you in the PM side. ( I cannot show garage posts in the open forum for obvious reasons).

Let me know, i've personally done these mods myself to my truck.

fyr145

Thanks for the help. I'll have to fully explore Lons Garage Member Section!!!:D :D :D :D

The owners manual on my wife's old 92 Accord actually said to defrost the windows you should leave the temp knob exactly where it was and simply engage the A/C button. I have tried this in several cars and trucks and it works like a charm.

I think it is because the A/C tends to dry out the air in the vehicle.

Originally posted by puppychop3
Thanks for the help. I'll have to fully explore Lons Garage Member Section!!!:D :D :D :D

PC,

Go to Lons' Garage section in the forums, head over to the "Lighting & Electronics" FAQ section, then open the "Heating & Air Conditioning" thread...........your answer and pic awaits you there.

fyr145

The A/C de-humidifies the air. Thats what makes the windows (at least the interior side) defrost faster with the A/C on. When it's cold outside, the humidity is higher, and then when a person jumps in the car, and is exhaling warm, moist air, the windows will fog up. You gotta get the moisture out of the air, and the A/C is the best way to do it.

With the A/C on with the heat cranked up all the way hot, the air is very warm. There really is no reason to disconnect the A/C defrost setting.

i've had mine disconnected for about 2 years now and it seems to work just fine without it. Never had any problems. My interior clears up with the heat turned over to max and set to the defrost mode.

Of course here in AZ, it doesnt get that bone chilling cold very often.

Originally posted by darth tundra
The A/C de-humidifies the air. Thats what makes the windows (at least the interior side) defrost faster with the A/C on. When it's cold outside, the humidity is higher, and then when a person jumps in the car, and is exhaling warm, moist air, the windows will fog up. You gotta get the moisture out of the air, and the A/C is the best way to do it.

With the A/C on with the heat cranked up all the way hot, the air is very warm. There really is no reason to disconnect the A/C defrost setting.

The point is that Toyota should have never have made it "automatic" for your A/C to come on by just turning the vent to defrost for the simple reason that: it defrosts fine EVEN WHEN BLOWING HOT AIR and a person can still stay warm at the same time while defrosting your windows. Maybe the A/C kicks OFF after it initially kicks on when the computer figures out that you want hot air instead of cold air to do your defrosting - now that would be OK, but if the A/C stays on the whole time regardless of your temp. setting then that is lame. :mad:

try this:

Turn on your A/C, put it on so it is blowing out of the vents in the front of the dash. Crank it all the way over to hot. The air will be HOT even though the A/C is on. Thats the point: the air is still hot, but the A/C is dehumidifying the air.

Almost all newer cars do this, whether you know it or not. It's not the hot air that de-fogs the inside of the glass, it's the dry air blowing over it. I'm not talking about de-frosting the outside (which obviously needs heat to remove the ice) I'm talking about de-fogging in the inside.

Yes, but it is hotter without the A/C and also starts putting heat out sooner. I don't live in an area with humid, rainy summer weather, so I pull the A/C wire off my defrost control switch. The few times when we all have wet coats, including the dogs, I switch the A/C on as needed.


Ken

Seems like everyone has their own preferences on this mod. Thats ok....to each his own. :)

I don't mind the AC coming on, what ticks me off is turning off the recirculation button... nothing like breathing all the fumes around Dallas while you're driving.. when I update the radio, I'm definitely doing both mods..

I don't care for the interaction of the A/C and recirculation functions with my selection of vents either. I prefer the way my Mazda does it. If I want A/C, I turn it on with a button. If I want recirculted air, I turn it on with a button. And changing the vent selection doesn't affect either of the other settings. I can set it exactly the way I want it.

To me this has always seemed to be a domestic vs. import (or at least Japaneese import) distinction. Domestics seem (in my limited experience) to tie these functions together, i.e. turning the A/C on when you select defrost.

Maybe the imports are trying to make themselves more familiar to the owners of doemstics in hopes of winning over more buyers.

I noticed a friend's new Hyundai Elantra also changes A/C and recirc settings with the vent selection.

Originally posted by darth tundra
The A/C de-humidifies the air. Thats what makes the windows (at least the interior side) defrost faster with the A/C on. When it's cold outside, the humidity is higher, and then when a person jumps in the car, and is exhaling warm, moist air, the windows will fog up. You gotta get the moisture out of the air, and the A/C is the best way to do it.

With the A/C on with the heat cranked up all the way hot, the air is very warm. There really is no reason to disconnect the A/C defrost setting.

Actually, not only are there heating advantages and recirculation advantages to disconnecting that "feature" of having the defrost work with the A/C, but if you do disconnect it you'll also save 5% in gas mileage (at least by my seat of the pants results). I would have thought that Toyota would have diconnected it for EPA reasons alone!

I think Toyota meant well, but it's more versatile to let the owner use the ac, defrost and recirc as needed. I definitely mix and combine in ways that Toyota won't let you do.

It's only optimum under certain circumstances and toyota uses it under *all* defrost situations.

alan

There are some good reasons why the system is designed the way it is.

1. As previously mentioned, the cold AC coils dehumidify the air as it passes over the coils.

2. Outside air is almost always lower in humidity than the air inside the cab, hence recirc automatically turns off when defrost is selected.

3. Periodically cycling the AC compressor in the off-season while in defrost mode helps to prolong its life by distributing lubricant throughout the system. This also helps to keep the seals and O-rings soft and pliable. This is probably one of the biggest benefits of automatically cycling the AC compressor on when defrost is selected. If you elect to defeat the automatic feature, it is highly advised that you periodically press the AC button in the off-season to cycle the compressor.

4. The AC compressor will not actually cycle on that much when defrost is selected in the winter where it is cold. The AC system in the Tundra is of the CCOT (cycling compressor orifice tube) design. When the AC compressor suction pressure drops to a certain point that corresponds with a refrigerant temperature just above the point that water freezes, then the AC compressor shuts off (the electromagnetic clutch disengages). As the temperature in the evaporator warms up, the AC suction pressure rises and the compressor cycles on again. Since the system is designed primarily to operate in hot temperatures, when the temperature is cold, the AC compressor rapidly drops the evaporator temperature to the point that the compressor cycles off. If you would start the truck up when it is cold, select defrost mode, and open the hood of the truck, you can see by watching the AC compressor clutch that the compressor internals aren't turning that much when it is cold outside.

Having said all that, I can fully understand why a person would want independant control of the AC and defrost functions. I might disable the automatic function myself if I ever have to remove the HVAC bezel for any other reason. If I do, I will just have to make a mental note to turn the AC on periodically in the spring/winter/fall for lubrication purposes.

<SNIP>Originally posted by arkie6
There are some good reasons why the system is designed the way it is.

3. Periodically cycling the AC compressor in the off-season while in defrost mode helps to prolong its life by distributing lubricant throughout the system. This also helps to keep the seals and O-rings soft and pliable. This is probably one of the biggest benefits of automatically cycling the AC compressor on when defrost is selected. If you elect to defeat the automatic feature, it is highly advised that you periodically press the AC button in the off-season to cycle the compressor.

<SNIP>

You got that right!.....I had to pay $600 for a/c repair to a '94 Mustang I had. I rarely used a/c in hot weather and never had a need for defrost cycle in the winter during one year. I'll spare you the details of the problem, but Service Tech advised me to turn on a/c a few times during winter for lube purposes, as you point out in the text above. Good advice!!

Is there a mod to keep the recirculating on regardless, I do not want to breath in what is out there somtimes but still need to see.

A/C doesn't mean "Air Cooler." It means air conditioner. It conditions the air. If you turn on the A/C and then set the thermostat to hot, then the A/C will heat the air. It isn't cooling the air and then sending to the heater to be heated up again, the A/C is the heater. Hope that clears some things up...

Howstuffworks "How does a heat pump work?" (http://home.howstuffworks.com/question49.htm)