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Old November 14th, 2017, 10:00   #1
badnews
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Default I want the A/C to turn on ONLY when I hit the button!

I haven't been able to find an existing thread on this topic (if there is one, point me!) so I started a new one. Hopefully someone has figured this out already.

I want the A/C to come on ONLY when I press the A/C button. Currently it comes on automatically when I move the air selector to any of the Defrost settings. It also comes on automatically, if Defrost is selected, when I turn down the temperature selector.

It can be 10% humidity and 25F, and the A/C comes on. Bloody nonsense!

Anyway, I think this is controlled from the VCDS (if it's not, is there a wire I can cut?). Can someone tell me WHERE in the VCDS this can be modified? And how to make it manual only?

Thanks.
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Old November 14th, 2017, 10:06   #2
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You may poke around in the Climate module and see if there is something in there that could change.

Given the nature of the variable displacement compressors, though, not sure it would bother me much that it works the way it does.
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Old November 14th, 2017, 10:30   #3
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Not what you're looking for but you can always turn on the defrost and then shut off the A/C. That's what I usually do if I don't want it running.
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Old November 14th, 2017, 10:48   #4
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Originally Posted by KITEWAGON View Post
Not what you're looking for but you can always turn on the defrost and then shut off the A/C. That's what I usually do if I don't want it running.
That's what I have to do now and it's really annoying. I live in a desert where the relative humidity is almost always low, summer and winter.
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Old November 14th, 2017, 12:17   #5
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Quote:
Originally Posted by badnews View Post
I haven't been able to find an existing thread on this topic (if there is one, point me!) so I started a new one. Hopefully someone has figured this out already.

I want the A/C to come on ONLY when I press the A/C button. Currently it comes on automatically when I move the air selector to any of the Defrost settings. It also comes on automatically, if Defrost is selected, when I turn down the temperature selector.

It can be 10% humidity and 25F, and the A/C comes on. Bloody nonsense!

Anyway, I think this is controlled from the VCDS (if it's not, is there a wire I can cut?). Can someone tell me WHERE in the VCDS this can be modified? And how to make it manual only?

Thanks.
No, actually it won't . . . Most systems lock out the compressor below a certain temperature to avoid destroying it by liquid slugging it (IE hydrolock).

Myself, I can't fathom running defrost without the AC . . . it just plain does not work nearly as well in most conditions. What exactly is the problem you are seeing, or is this more one of those "principle of the thing" kind of issues?

- Tim
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Old November 14th, 2017, 15:12   #6
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Tim,

If I lived in Texas, or any other warm, humid place, I'd probably agree with you. I grew up in Michigan, so I know what it's like. But I live on the high plains and drive a lot in the mountains: land of body lotion, chapstick, "dry-eye", humidifiers and static shock. Cereal never gets stale when you leave the bag open.

Because of the high altitude, the thin air never holds much humidity. Have you ever seen snow sublimating in the sun at 15F in Texas? It is quite normal here.

The number of times I've needed/wanted to run the A/C to defog in the last 30 years I can count on the fingers of one hand, that is, if I could remember that far back. If it's cold enough to need to defrost, the A/C is ineffective anyway.

On sunny fall/winter days, I like to have fresh air on my face/shoulders (which are in the sun) with the Defrost setting, without chilling my body and feet.

Recently there have been a number of days where I started with the heat full on. As the day and car warmed up, I turned down the heat bit by bit. Suddenly I was freezing because the A/C came on unexpectedly. It was about 50F outside. Bogus.

And as I said, running the A/C when it's not needed is a waste of fuei and puts unnecessary wear on the compressor.

So I find it annoying. I disabled it in my previous vehicles but it's my understanding that I can't just cut a wire, but need to change the VCDS in this car.

I'll take any advice on this.
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Old November 15th, 2017, 23:01   #7
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I grew up (and still have a home in) Northern Michigan, and that is where the experience I drew my comment from was had. No AC on defrost pretty much meant no visibility during those times of year you could actually get a window to fog and not freeze. And the low temp AC cutout applies everywhere . . .

Last edited by tadawson; November 19th, 2017 at 21:18.
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Old November 19th, 2017, 05:29   #8
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I have found this feature quite annoying on my MK5 as well, especially when you are trying to thaw ice off the windshield with a cold engine. I know the AC has a cold lock out but would like the option of choosing when to turn the AC on.

Might have to poke around with VCDS and see if I can find anything.
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Old November 24th, 2017, 09:24   #9
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Quote:
Might have to poke around with VCDS and see if I can find anything.
I did that about a week ago and it doesn't seem like there's a way in the VCDS to do this. We might need to do some wiring changes.
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Old November 24th, 2017, 12:35   #10
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Same here. I would like to switch that "Automatic A/C on" feature unless I specifically hit the AC button.

Once I select the "AUTO" feature - it automatically switches on the "AC" too.
Once I select "defrost" it automatically switches on the "AC"...

Each time I have to click twice (one click to switch the AC off).
In my climate zone, I use the A/C very rarely, like a few times a year.

I'd be also interested in ability to switch that automatic AC-on feature, which is really annoying and requiring useless clicks on day-to-day operation.
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Old November 24th, 2017, 12:44   #11
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Maybe it's time to splice into the wire(s) going to the AC Compressor Clutch and set-up a Relay with a toggle switch mounted below/under the dash. You could toggle the compressor off at will.

Seems the Fan Control Module (FCM) is located on the back of one of the fans on the later models (maybe beginning in 2006) ... is for the 2008 Eos Gasser. Anyway, if you could determine which circuit activates the FCM in the AC mode, a Relay could be set-up to eliminate both the AC Clutch and Fans. Seems the Temp Sensor wiring is separate for the purpose of turning on the fans based on engine temperature.
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Old November 24th, 2017, 12:54   #12
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There is no such thing as AC Clutch on these cars... The compressor is turning all the time, it just uses variable geometry based on cooling demand.

But still, I'd prefer for the AC button to be inactive by default, unless I turn it on manually.
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Old November 24th, 2017, 14:07   #13
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Quote:
Originally Posted by Henrick View Post
There is no such thing as AC Clutch on these cars... The compressor is turning all the time, it just uses variable geometry based on cooling demand.

But still, I'd prefer for the AC button to be inactive by default, unless I turn it on manually.
Well, I wasn't sure if the 2015 did or did not have a compressor clutch.

So, why not do the same for the Compressor Control Valve Solenoid? ... if possible. Any workable method to modify or fool the system should also include the fans out front.
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