Anyone disable automatic AC with defost functions?

[great white]

I've just about had enough of this AC automatically "on" with defrost/defog.

Yup, I know why they built it that way (drier air for defogging).

I'm smart enough to decide when I need the extra umph from the AC to clear the windows.

Plus, there's not a lot of moisture to pull out of the air -20 to -30 Celsius.

Ever since manufacturers started making the decision for you, I've despised it and have found ways to defeat it on most of my cars.

Usually, it's a simple matter of cutting a circuit trace in the control head.

Anyone try it yet on a 96+ truck?

Or have a diagram of the circuit trace?

I've got my spare on the bench right now tracing it out....

 

[THEFERMANATOR]

If it's that cold the A/C shouldn't be coming on anyways. A properly charged A/C won't come on below freezing due to the low pressure cutoff switch. As for disabling it, you would have to open up the A/C control head and bypass it that way. I believe teh defrost function simply trips a switch when you turn it all the way over.

 

[great white]

If it's that cold the A/C shouldn't be coming on anyways. A properly charged A/C won't come on below freezing due to the low pressure cutoff switch. As for disabling it, you would have to open up the A/C control head and bypass it that way. I believe teh defrost function simply trips a switch when you turn it all the way over.

Good points Ferm, but I don't want it coming on in summer either.

Canada has a little bit different humidity issues than down south (well, different all across Canada too).

The rotary switch is a "microswitch" design. I think I've got the right circuit trace figured out (only comon one between the AC switch and Rotary selector switch) I've just got to break it and try it out.

Problem is, finding the time to actually do it right now is tight....

 

[88gmctruck]

Ask and you shall receive. Looks like it's a detent in the switch....

Let me know if you need any other diagram. I have access to them for the 99.

 

[great white]

I've got that one in my FSM also.

I definately see where the Mode selector bypasses the AC switch.

I just need to figure it out on the PCB....

 

[Acesneights1]

During the winter months it's good to run the compressor or the seals can dry up. I like the feature personally.

 

[jrsavoie]

I thought that was the whole purpose of having the AC run with the defrost.

During the winter months it's good to run the compressor or the seals can dry up. I like the feature personally.

 

[great white]

I thought that was the whole purpose of having the AC run with the defrost.

Sure is.

Thing is, it's not always required ( ie: cold of winter or humidity is low) and costs mpg/power during these times when not required.

Ac is only needed during high humidity and "defogging".

It's essentially pointless when "defrosting".

Besides, I'll choose when it runs myself.

Thanks but no thanks gm...

 

[jrsavoie]

You could splice an on/off switch into the hot wire going to the pump. I did that on one of my vehicles. I think it was the purple wire

 

[great white]

You could splice an on/off switch into the hot wire going to the pump. I did that on one of my vehicles. I think it was the purple wire

That's not a bad idea actually.

I still have to pull the control out of the dash and trace down the cicuit paths. There's a bypass in there somewhere, I just have to see if it's internal to the switch or on the PCB...

 

[dangerousdave]

At the compressor, I cut the wire to the clutch and ran a switch to it. No need to trace circuitry.

 

[Heartbeat Hauler]

I'd like to be able to use Recirc for heater. Way too much cold air comes in when not in recirc.