I know Neil has this on his truck but has anyone else done the AC mod. I looked in the how to forums but no luck. The ac mod is basicly a switch in the cab to turn the ac compressor on and off. Well more importantly only let it come on when you want it on. How is it done ?

 

Just go to the back of the HVAC panel and interrupt the solid purple wire coming out of it, using a SPST (on/off) switch. When the switch is off, it will kill the AC-enable signal to the PCM and the compressor will not operate.

It is a good idea to run the AC compressor regularly to keep the compressor and seals lubricated, even when you don't need it for comfort. Ford's solution was to make it run almost all the time. Anyone who does a mod like this should make a point of running the AC compressor on a regular basis.

 

is there really a good reason behind doing this? when else does the compressor cycle besides ac and max ac?

 

The compressor is enabled in every setting except OFF and VENT.

 

The compressor is enabled in every setting except off, vent, and floor.

 

According to Ford's factory 2001, 2002, 2003, and 2004 factory Wiring Manuals, the compressor signal to the PCM is disabled in OFF and VENT only.

EDIT: It has been verified that the factory info is incorrect. The correct info is that AC compressor operation is not allowed in OFF, VENT or FLOOR.

 

ok so put a switch in-line with the purple wire got it. Neil has a very factory looking switch any idea where I can get something that looks semi-factory.

If I run the compressor once a week is that good enough ?

I think its really dumb that the compresser runs that often.

 

im still not getting the benefits of this?

 

not running the A/C compressor will eliminate the power robbing action of turning the compressor when not needed
if you want to chill the air or defrost your windows quickly, just turn it back on on
when temperatures are moderate why run it?
turn it off and just bring in fresh air via the vents
in the winter I use my defroster when needed (almost every time I start up the truck) and lubricate the compressor at that time
in the summer if it is hot enough, I close the windows and run the A/C
the compressor runs in all HVAC postions except off, floor, or vent
on LIL BLUE I am sure of this because her A/C indicator light will illuminate unless I have it switched off
I believe it saves fuel, especially on the highway in moderate temperatures and in the winter

 

Yea, it definately shuts off on floor. Unless I need to defrost the windshield or I am actually using the AC, the selector is always on floor. Saves the fuel as well as wear & tear.

Now that you've mentioned this, I think I'm going to do this mod tonight.

 

You guys got me thinking about whether the Ford literature was right or wrong. Since I couldn't verify it on my truck with EATC, I dug up my original manual HVAC panel and bench tested it. Sure enough, the AC-enable wire is hot in all modes except FLOOR, VENT and OFF. Hard to believe that they carried the error over for 4 years, possibly more. Knowing what I know now, I'll bet if one was to look at the 2005 documentation, it would still have the same error.

 

Wow, that's one of the first mods I did for my truck, and I've had the info up for probably 3 years. I guess no one ever checks my webpage :(

http://silvertank.batcave.net/ACmod.htm

 

isnt vent the one with the arrow pointing at the guys head? if i have the selector on the head and foot arrows, is my compressor running?

 

Yes.

 

well George I do not know what forum provided me the link to the G&M A/C MOD, but you are the one that prompted me to perform it
according to your site the instructions have been up for 2 years, 1 month and 1 day

 

Factory configuration:

AC Compressor operation allowed:
Max AC
AC
Vent/Floor
Defrost/Floor
Defrost

AC Compressor always off:
Off
Vent
Floor

 

Now, why does it seem that using the the "AC" and "MAX AC" settings provide colder air than just the defrost and vent/floor settings? Does the compressor run a shorter duty cycle on defrost & vent/floor and longer on AC & MAX AC?

 

might have to do with the postion of the blend door
in the winter when I wanted to heat the cab faster I put it on MAX AC with the compressor switched off
the air blowing out did not get as hot as when the HVAC switch was in in vent or face
I suspect the routing of the air was blowing more over the AC exchanger than the heating fins
same would go in reverse when using vent, face or mix to bring in the coldest A/C treated air - it might not happen

 

I had a 91 Eclipse GS and I really think Ford's AC controls are now archaic compared to how much control you had over the AC in that car. In the Eclipse, I was able to pretty much control everything. I liked how it was set up and was kind of sad how the controls were in my Ranger.

 

Compressor is OFF, positions vent, floor, off on mine too.

 

I'm just wondering why you would want to go through the hassle of doing this? On my 2002 FX4 i checked mileage both ways (with and without a/c) and found that there was no difference at all.

 

Depending on the conditions, it certianly can save some gas, restore uselessly lost power, and reduce the wear on the compressor. It's also quieter.

 

It could definitely be colder on Max AC because the previously cooled air is being recirculated from the interior through the evaporator and back into the interior. AC, VENT/FLOOR, VENT/DEFROST and DEFROST all use outside air instead of recirculated.

The duty cycle of the compressor is determined by a pressure switch in the system that is set to prevent condensed water from freezing on the evaporator coil. The duty cycle may be slightly different in the various HVAC selector positions but it is not dictated by them for any cooling purpose.

In almost any car/light truck, the AC system runs continuously at its maximum available output whenever it's on. The temperature can only be regulated by working the heater against the AC. In a Ranger, the temperature selector **** moves the blend door to mix heated and cooled air together to achieve the desired temperature.

 

Ok. Is it just me or could ford have done a much better job labeling the HVAC controls. They make it look like the AC only runs in the two AC positions which is horribly misleading. I've always prefered the configurations where you have a selector for where the air goes, a selector for temp, a selector for fresh or recirc, and a button for AC.

 

I think it mostly comes down to warranty. If you allow recirculation on only one AC setting, you reduce the likelihood of mold buildup in the plenum. If you run the compressor regularly in the winter and summer, it keeps the seals lubricated and you reduce the number of seal leaks that happen. Also, having the AC run in the defrost modes helps defog the inside of the windshield faster by dehumidification.