Defeating A/C cutoff at WOT?
 

I drive between 800-1000 highway miles a week, and if I'm merging into 80mph traffic and don't feel like downshifting into 3rd, I can sometimes spend up to 30 seconds at WOT, or near enough to it for the fan to blow alot of 80-90° air in my face, which really sucks when I'm just leaving work and I'm hot and sweaty. Obviously I don't want to permanently disable this feature, but what I'd really like is a switch somewhere that I can hit to bypass the feature and keep the A/C on at WOT.

Any ideas on how to do this *cough*Bob Rwenzing*cough*?

you could always wire the compressor to a constant source and put a switch on it. this way when you know youre going to get on it then you flip a switch and the ac stays on.

you guys are gonna blow a motor or somethin. doin 80 and wanting to downshift!! into 3rd!! are those 3 L really that slow that you cant keep it in 5th and still get gettin?

I have 4.10s, I can do 70mph in 3rd gear. When you're stuck behind grandma moses doing 15mph on the on-ramp to I-95, where the speedlimit is 70, and the traffic is going 80-90, you bet your sweet ass I want to downshift and get going as quickly as possible! :shrug:


My concern with wiring constant power to the compressor is that I might be sending too much amperage to it when my constant power is on AND the factory signal is on. I'd much rather find a way to interfere with the signal that tells it to shut off at WOT.

That would work, but you have to remember to shut it off. If you don't, you'll be bypassing everything else that shuts it off such as low pressure and freeze switches.

Yeah, I'm actually considering making it a momentary switch so that I couldn't leave it on, or at the very least wire in a relay so that it will reset when I turn the key off.

edit: I wonder if I can get a mechanical switch that will close a circuit for a certain amount of time and then open it again?

1,000 miles a week???/ HOLLY ****.

How many miles are on your truck??

45K

Amps are not sent. They are drawn. Your compressor will draw the same amount of current regardless of where the power is coming from. You could put a 4 gauge wire direct from the battery to the compressor and it will draw the same current as the wire from the computer.

Even still, a second power supply would have to come from somewhere, that adds the hassle of either overdrawing an existing circuit, fabricating a new fuse location in the fusebox, or just running constant battery power, NEVER a good idea for circuits that don't have their own power interrupt (like amplifiers.)

On late model Fords, the PCM has full control of the compressor clutch by supplying ground to the A/C clutch relay coil. The PCM uses the function selector switch, the A/C cycling switch, the A/C high pressure switch and its own internal maps to decide when to supply that ground.

It appears that you can just jump around the PCM to enable the A/C compressor operation whenever you please. This would still allow the cycling and high pressure switches to operate as they should. Of course, I haven't tried this so, once again, Brian, you would get to play lab rat.

There are two wires that run between the large 42-pin connector on the DS valve cover and the PCM. The wires you are looking for are both 20 gauge:

black/yellow to pin 86 of the PCM; and
pink/yellow to pin 69 of the PCM.

Tapping into these two wires and providing a switched wire between them would give you the option of overriding PCM control by closing the switch. When the switch is opened, it would return to normal production operation.

Side effects:

This shouldn't harm the PCM in any way and I don't anticipate any CELs from it either. You would be spinning the compressor considerably faster since it would be enabled at WOT/high RPM during the onramp accel. Full size Ford pickups and vans do not have a WOT cutout on the A/C, so you're not breaking new ground here.

You will see a couple of changes (only when the switch is closed):

(1) You will notice a difference at idle, though, if the switch remains in the closed position. In the factory configuration, the PCM anticipates the coming load of the AC compressor about a half second before actually applying it and ups the flow through the Idle Air Controller to compensate. This proposed bypass wouldn't allow the anticipation, so there would be more noticeable dips and flares in the idle speed as the compressor cycles.

(2) In addition, closing the switch would effectively bypass the dash control, meaning that when the switch is closed, there would be A/C compressor function allowed in all 8 selector modes. When the switch is open, the selector would function as it does now.

Switches:

If you used a pushbutton, you would have to hold it continuously to keep the compressor spinning at WOT.

If you used a toggle switch, you would need to remember to open the switch when not needed.

Thats exactly what I needed to know, now I'm just going to look into either finding a mechanical timed switch (i.e. a switch that will close the circuit for ~30 seconds then open it,) or devise some type of timer circuit using a relay. I would be using this feature almost exclusively for on-ramp merging, or making "short moment of opportunity" acceleration runs to get around/between/ahead of the 18 wheelers that seem to delight in clogging up I95 as much as possible. When you're doing 55, and at the end of the passing manuever you're doing 90, it takes enough time to notice the A/C cutoff.

I was aware that full-size Fords do not have this feature, specifically for towing on inclines, where WOT could be maintained for long periods of time.

You might be able to use a vacuum operated switch. They used to sell them to provide the WOT cutout on vehicles that didn't have it from the factory. Maybe you could use the same switch with a relay to reverse the switch logic. Sort of a "WOT cut-in". If you could make it work, the operation should be completely transparent.

Thats an idea, but I don't want to permanently disable it, just selectively in the situations I explained above.

To me, downshifting seems preferable to holding down a momentary switch.

well you wouldnt have to hold it down if you put it on a timer (if possible). So you press it once, it disables it for 60 seconds or something like that.... although I agree, id rather just downshift than mess with all of this!

Well even if I downshift, honestly the 3.0 isn't a rocket in 3rd gear or higher, so I still end up spending alot of time getting up to 80-90mph when passing traffic. I assure you that I wouldn't want to hack up my truck's wiring if I could get the desired results without doing so. ;)

Obviously, this mod isn't for everyone, I wouldn't expect it to be popular, and I'm not even going to write a how-to on it, but with my style of driving, and my unique circumstances, if I could do this discreetly I think it would make my afternoon ride home just a little more enjoyable, and when the ride is 1-2 hrs in heavy traffic, every little bit counts towards my overall sanity.

I still want to know why ford still uses the "retard" climate control.
I much prefer the mazda (i think) or import type controls..
Where you select if you want the a/c on .(button) and a 6 position knob for the vents controls.

Rand

Nah, you just need button on the throttle body, or pedal. Just like a Nitrous switch to close the circuit on WOT.

Maybe you're not all understanding, I don't want the A/C to stay on at WOT every time, only in situations where I know I'm going to be at WOT for more than a few seconds. Obviously if I'm at a light and I'm just flooring it for a few seconds to get ahead of grandma before the lane ends, I don't mind the A/C cutting out, because I could use the few extra HP.

wear lighter clothing.... :wink:
good luck Brian, sounds like a good plan