AC modifications

[GMC Hauler]

I got tired of the AC turning on automatically when i turn the mode knob to any sort of defrost. So i figured out how to bypass that: Remove your control center from your dash, and on the underside, there is a trace that runs along the edge of the board. Where that trace runs into the solder joint for the mode control switch, cut it (I used an exacto knife).

You can also force it to allow you to be able to use recirc door at any time, by soldering 2 pads together.

[JeepSJ]

They run the AC on defrost so that it dehumidifies the air. Just curious - why do you want it off?

[GMC Hauler]

They run the AC on defrost so that it dehumidifies the air. Just curious - why do you want it off?

Sometimes you don't need to defog the windshield, just defrost the windshield with heat.

The AC defog's the inside
The Heat melts the snow and frost off the outside.

Many times, the heat is enough to do both without using the AC

Another example: It is wintertime, using outside air, less than 32F. That means that the outside air is already defogged by nature. All you need is heat.

[DmaxMaverick]

It runs on defog for 2 reasons. One is to run the system year round. Leave an A/C system idle for 6-8 months, and it may not work when you need it. Bad for seals and the compressor. The second is as Jeep said. Sure, it may not appear to need a defog if it's cold enough, but once your warm body gets in, and your breath hits the air, any airborne moisture will adhere to any cold, nonporous surface, like glass. It also does on other surfaces, but you aren't trying to see through those. Try driving w/o breathing toward the windshield.

Does the compressor still engage in defog when you press the A/C button?

[GMC Hauler]

Does the compressor still engage in defog when you press the A/C button?

Of course.


You can still use it if needed, but you aren't forced to.

You know as we'll as i do, many older cars did without this for many of years. Most old cars operated this way. I drive on every day in the winter, without any form of AC

[Robyn]

Hmmm I see what you are saying but I guess I dont understand why you are saying it.
Now here in western Oregon it rains a lot and when it is not raining its about to.

Here at the ranch we are in the clouds anytime there is a storm in from the coast.

Having the AC come onn with the system is a real plus as it gets rid of all that extra moisture in the cabin and it does it very fast as compared to just the warm air blowing.

Now if you live in an area that is fairly arid the need is probably not as great.
Even so as Maverick mentioned the setup serves the purpose of keeping the system in good order by running it on a regular basis.

My Big truck is set up the same way with the AC running in defrost mode.
The truck gets run in defrost most of the winter and in AC all summer.

The rig has 549000 miles on it now and it still has the factory compressor on it doing what it was meant to do. Now this compressor is basically the same unit that GM runs on the 97 and newer pickups and Burbs.

Guess if it will do 500K+ there is not much worry about it going south on the grocery getter.

Best

Robyn

[GMC Hauler]

Hmmm I see what you are saying but I guess I dont understand why you are saying it.
Now here in western Oregon it rains a lot and when it is not raining its about to.

Here at the ranch we are in the clouds anytime there is a storm in from the coast.

Having the AC come onn with the system is a real plus as it gets rid of all that extra moisture in the cabin and it does it very fast as compared to just the warm air blowing.

Now if you live in an area that is fairly arid the need is probably not as great.

Agreed. I lived in Washington State for 3 years. You do need the AC for dehumidification. When I lived there, 2 of my vehicles had ben modified. I just pressed the AC button.

However, if you live somewhere where it frequently goes below 32F, then this is where it really pays off. The air is already dry because of the outside temperature.

Being in the military, you get to see many different climates.

This can be very useful in the Northeast most of the winter. The further north you live the the more useful.

I have used vehicles where the dehudumification effect provided by the AC made the defrosting effect much less powerful.


Even so as Maverick mentioned the setup serves the purpose of keeping the system in good order by running it on a regular basis.

Roger that, you are all correct in exercising the seals and moving the oil in the AC system. I provide this mod because most people here, upon knowing that fact, can exercise the seals themselves by pressing the AC button for a minute or so every day/week. The builders provide that "built in feature" for the masses who aren't as car savy as we are.

[Hubert]

Remove your control center from your dash

How do you do that? Do you take the whole dash off to access the control center?

My mode switch doesn't appear to work anymore and my compressor doesn't come on with the fan on. It will cycle with fan off briefly on and off turn the fan on and compressor disengages and won't reengage. So I suspect the control board is bad.

[GMC Hauler]

How do you do that? Do you take the whole dash off to access the control center?

My mode switch doesn't appear to work anymore and my compressor doesn't come on with the fan on. It will cycle with fan off briefly on and off turn the fan on and compressor disengages and won't reengage. So I suspect the control board is bad.

You pop off the front facia. Mine comes off with a little pressure provided by my hand. Then, use a flathead screwdriver to gently pry the tabs for the control unit (there is a tab on each side, hidden)

[joed]

I've noticed that if you put the mode selector switch between heat and heat/defrost, with it closer to the 'floor' position the a/c won't cycle. You still get some flow out of the defrost vents, just not quite as much. Moving to the defrost/heat position will then cycle the a/c and increase the defrost flow.

Another thought...

Joe.