tvc15_2000

When the defroster is turned on the AC starts (even in very cold weather) - Presumably to dehumidify the air.

There are times when I want just the defroster on and no AC pump running. At one point Scion informed me to press the AC button on and off once and this would turn of the AC. I have tried this and it does not work.

Has anyone figured out a way to have the defroster on and no AC pump running. I know if I turn off the fan and just use air circulation from driving - this will work. But I would prefer to have the fan running - and not the AC.

Of course there are times when having the AC run is desireable. But I would like the choice for the conditions.

Thanks

burstaneurysm

Mine doesn't do that...

Night_Shadows

Mine either.

xbsors

neither does mine

J1slim

when the selector **** is turned to defrost the a/c will turn on.....this is correct, the light on the a/c button will not be on but the pump should still be running. How to turn it off not sure. Is there anything in the manual..???

tvc15_2000

You may or may not be aware it is happening. You can check by setting your defroster on and turn on the fan blower. Then look under the hood at the window on condenser for the AC, I think its the condenser. The thing with the window on it. If the bubble is moving (as mine is) the the pump is running.

If you turn off the fan setting it will shut down.

Another test is to put your temp to cold and you will feel the AC blowing cold air.

My concern is when just running the defroster it impacts fuel economy and in my opinion is a waste. If I need the AC on - I would like to turn it on or off!

LeroyJMC

You can't turn it off. Defrosters are designed to work this way as you presumed initially....to dehumidify the air.

stew32

Usually, it's on the switch to change to vent setting. It's pretty much standard on vehicles to kick on the A/C compressor in both defrost and floor settings. I don't like it either. There's probably a switch you could bypass. Otherwise, I'd just avoid putting in defrost unless the windows really start fogging or you need the heat to melt ice on the windshield.

mrfuzzy4

move to a warmer place! snow sux, and makes some hardcore pain for cars! *cough michigan bites ***** cough* *cough potholes and cold and construction and... more potholes duh cough*
i wouldnt worr too much, couldnt make that big of difference!

pollock3s

Make sure you switch the recirculating air to fresh air when using the defroster.

ajayaitch

I had an old Mazda Protege that used the same setup, AC on with defrost. The AC quit on me one year, so that winter was a total _____. You'd think hot air was enough. Oh no, this was hot, MOIST air. I had to carry around a beach towel. Seriously, it was worse than driving my Volkswagen Baja. And it wasn't just the windshield. Drive long enough and you'd think a couple of horny teenagers were swapping spit in the back seat while I chauffeured them around town. Every window was fogged over.

peteski

So what you're saying is that the AC compressor turns on in defrost mode even when the light in the A/C buttton is not lit? I thought that the A/C button being off would fully disable the AC. I suppose that I'll have to check that myself.

But you're correct - this is done to dehumidif the air to better defog the windshield.

tvc15_2000

That is correct. When the defroster is on the AC goes on if you want in on or not. It goes on if the AC light is on or not.

This is an option on most cars. The driver usually is trusted to decide if the conditions require the use of the AC.

Most times its not needed and in winter it is a waste to use the AC to generate heat!

Dehumidifying the air is definatly not a requirement in most cases and if your doing a lot of low speed stop and go driving it will reduce your gas mileage when compared to no AC and just a defroster fan.

Again you can check for yourself by looking at the bubble window on your AC under the hood.

Most auto makers offer a way to turn off the AC in defrost mode for the obvious reason its not needed most of the time.

You can turn off the fan and have the controls set to defrost and air circulation alone will work on a highway - but not in stop and go driving.

I am looking for a work around to control if the AC goes on - if someone has figured it out - rather than try bla bla bla.

Last year Scion said turn the AC button on once and then off and it would shut down the AC but that has not worked.

vintage42

The AC is interlocked with the Defroster air control ****, and yours does that unless you have rewired the controls. As the Owners Manual says:

LeroyJMC

I haven't heard of it being an option for any car....could you please state the year/make/model of the aforementioned cars?

Night_Shadows

I was reading through my owners manual last night and I read about this. Yes the a/c does come on, I guess I just never paid attention to it.