A modification to save gas and breathe smokeless air on long hills.

[don-ohio]

I'm gonna install an AC cutoff switch soon so I can keep the AC set on max(which is recirc air) on long hills and when a smoking,polluting semi-truck or other is keeping me from putting the AC selector to normal AC.
I make several trips a year to and from FL and Ohio and always take the van because of storage capacity.
I'm tired of moving the selector to OFF or vent when going up a long hill, when I COULD just punch a rocker switch for the AC clutch .
Yu guys/gals understand what I'm saying? I have the 15 AMP rocker swith and its mounting holder. I looked at the schematic and it looks like I can interrupt the AC clutch wire past the hi-pressure cut-off switch.
I've got a lot to do before going North again,but I'd really like to get this done. don-ohio

 

[BrooklynBay]

Do you want to shut off the fan blower with the compressor (kill the whole system)? The cut off switch is only for the compressor. The blower is a separate circuit.

 

[don-ohio]

No,Brooklyn, I want to be able to let the recirc air keep going. That takes longer for the interior to heat up as you progreaa up the hill. Don't want to kill blower. I hadda cut a bunch of trees down today,just small nuisance trees cluttering the yard. If I can, in the next few days,I'll get that cut-out switch installed.
Thanks for your input. Sometimes a person starts to do something and someone else can help him/her to do it better. don-ohio

 

[BrooklynBay]

The outside air will come in if the blower is on. Some vehicles have an electric actuator for blocking the air from the outside from coming in. How do you want to recirculate the cabin air?

 

[don-ohio]

The outside air does not come in when the blower is on and the switch is set to MAX air. Of course a LITTLE comes in, but very little (compared to NORMAL air) makes it in.
Some vehicles let more in on recirc than others,but an Aerostar seals most outside air out pretty well for the short time needed on hills.
I had a 1971 F-100 and if you put it on Max air, it sealed it all out. I was o a dirt road once following a rock truck for miles, and dust roared in before I got it purt on MAX air, which is recirc. After I got it into Max, I could detect no dust in that truck cab.
don-ohio

 

[BrooklynBay]

So you just want to deactivate the compressor clutch? You could wire a switch in series with the pressure switch or the relay.

 

[don-ohio]

Yeah,Brooklyn, I re-read my post and I guess I didn't make that clear. The switch will kill the power to the AC clutch only. That is why I said AC cut-off, which it effectively does.
It's a simple mod, but will save gas and limit our diesel fume exposure.
Do you remember the old Fords and Mercs that had the square,blue lighted button that did this? Worked like the flashers button..........push once to activate and it stayed pushed in.....then push again to deactivate and it popped out.
I think my oldest Aerostar,which was an 87, OR an old pinto may have had that button.
I'm not sure if that button deactivated the AC clutch when defrost was selected?
don-ohio

 

[boominXplorer]

I've been considering a similar mod for my ranger. I just want a simple on/off button for the ac compressor. On my truck I could interrupt the violet signal wire coming out of the hvac dash unit to control the compressor.

 

[don-ohio]

If you have the simple,2-wires to the AC clutch,it should be no problem. But I made sure I purchased a 20 amp rocker switch. A light duty switch could cause clutch burning. don-ohio

 

[Mbrooks420]

I wouldn’t bother with a high current switch, I’d just use a relay close to the compressor. I doubt a switch that was not up to the amperage would hurt the clutch, it’d just potentially weld the switch contacts closed or burn the switch up(possibly literally, with fire)

 

[BrooklynBay]

The clutch should have a relay near the battery. There are several relays at that location. The switch is wired to disconnect power going into the coil of the relay. The low pressure cut off switch might be on this side of the circuit but I'm not sure unless I see a schematic.

 

[don-ohio]

I looked at the relays,Brooklyn, and it looks too much of a chore to try to get the wire I need before the relay. I will just interrupt the power to the compressor clutch and see how it works. I'm still trimming trees, so I haven't gotten to this yet. BUMMER! don-ohio

 

[Mbrooks420]

Why not just use the MAX air setting and have it recirc the inside air? I don’t see the benefit to stopping the clutch.

 

[don-ohio]

Why not just use the MAX air setting and have it recirc the inside air? I don’t see the benefit to stopping the clutch.

Stopping the AC compressor not only gains you HP on the hills,but the trans and engine run cooler. WHEN you start back down a large hill,the you click the AC switch and the stress is off and gas has been saved. It's common sense. Why do you think FORD has an AC cutout hooked to the throttle? If you are straining for HP, the AC clutch disengages.

don-ohio

 

[Mbrooks420]

I guess I just never have any lack of hill climbing ability.

 

[don-ohio]

Quote MBrooks: I guess I just never have any lack of hill climbing ability.


It's not about ability.My van will blast up those hills,but use a lot of gas doing it.
I'm retired now and every gal of gas I save helps the budget. This is about saving gas and not breathing diesel fumes.
My next trip in a coupla weeks will be 800 miles in the Aerostar and a lot of small mountains(blue ridge,appalachia,etc.) . When you travel these mountains,the semi trucks are belching loads of fumes,trying to keep their speed up these hills.
The effects of doing this will also benefit my engine and trans. It's a win-win for me.

 

[don-ohio]

Brooklyn? I looked in my old Haynes manual,generic I know, but I didn't see a connection to any relay concerning the AC clutch . Maybe they just showed the wrong diagram or I am missing it? don-ohio

 

[BrooklynBay]

I couldn't locate a schematic for the 1994 but I found one for a 1996. The relay says wide open throttle (WOT) cut off relay: 96 ford aerostar: a/c compressor wont come..tested..high side..clutch…

 

[CDW6212R]

All of the cars have a WOT relay for shutting the power off to the AC clutch. The clutch power runs through that WOT relay normally, and a trigger wire from the AC controller makes the relay stop power at WOT.

If you place a diode in the existing trigger wire to that WOT relay, you could then add another trigger signal with a switch you choose. That is a low power circuit, the trigger side of the relay, any switch you like will work.

I suggest creating a switch(and a vacuum switch/solenoid) to force the recirculate door to stay in place, like the MAX setting already does that. I've thought about both of those ideas long ago, aiming to add two tiny switches to the bezel next to the EATC controller. I much prefer recirculate to letting in outside air 99% of the time. I'd rather have control of what's going on, and not the machine/car/manufacturer.

I run my AC on MAX while delivering mail, when it's above 80 or so, with just the one RF window down. I set the temp to about 72 and it blows a mild speed of air, colder than if set to automatic. My first mail vehicle I got tired of the AC clutch shutting off a lot normally. I put a fuse in the wires of the low pressure sensor, which bypassed the sensor, keeping the clutch running constantly. I did that with about 230k miles on the car(and clutch). It went another three years and 80k+ more miles, before the compressor died. I'd do that again if I thought the air wasn't cold enough for me(window down). The old 86 Crown Vic wasn't the best AC back then, my upgrade made it better.

Do what you have to do, to make it do what you want.

 

[don-ohio]

Thanks,Brooklyn! That's a better schematic than the Haynes. I appreciate the help. don-ohio