A/C cycling idea
 

I read a lot of posts about manually turning the a/c on and off depending on conditions, and it got me to thinking. i hope this idea hasn't been discussed into the ground already, i did some searching and didn't find anything like it.

basically A/C on when at low throttle(or just idle), off at higher rpms. how about being able to adjust it manually once for your taste?

basically the A/C compressor clutch is turned on/off by 2 wires at the compressor. interrupt one of those wires with a relay.

hook up the wire that activates the relay to one of those switches that turns off your riding mower when you fall off. hook the other end of the switch to an ignition-on power source.

mount the mower seat switch above the gas petal under the dash. hook a wire to the gas petal so that when you are idling around, the circuit is complete and the relay for the a/c compressor is activated. when you press down the gas petal more, the (mower seat) switch opens and the compressor turns off.

you may have to use a spring to make the switch return to "on" easier.



sorry, it was hot outside today and i got thrown off my lawnmower. maybe this idea is a result of that, instead of inspiration.

thoughts?

I used to have a '95 Chrysler LHS. I was told the computer controlling the A/C was part of the transmission control computer and would colst about $1500 to replace. I went to a local independent electronic store and bought a kit with an adjustable relay. I hacked in to the power to my compressor and ran that wire into the pass. compartment to my relay kit. I powered my board by adding a lighter adapter. When I wanted A/C I plugged it in, then used the adj. knob to find a comfy setting. Used it two summers until I got rid of the car.

Even better. That wire going to the compressor is somehow controlled by a wire coming out of your climate control unit on the dash. Find that wire. It's far closer to where you need it. Plus, it's usually a low-current wire, whereas the compressor is fed by a relay.

When I added AC to my CRX, I couldn't get the ECU to control the compressor. During troubleshooting, I wanted to make sure the compressor was working and hot wired a switch to the compressor relay. (on a Honda, the compressor relay coil always sees +12V, the switch is connecting the other side of the coil to ground). Finally gave up and that switch is what is turning my AC on. The pressure switch is inactive, but I make sure I don't leave it on for more then a few minutes at a time and it seems to work fine.

I connected another switch to the AC fan relay. The only headache here is that the idle speed doesn't increase to make up for the AC being on.

It also gives me the option of turning it off when acelerating, on hills, etc. Though you could do that with the standard AC button, if I ever got it to work.

So did effectively off/on the AC like a thermostat? I never trust climate control because they tend to just leave the compressor on and blend in some heat to regulate.

My only concern is if it's needed for throttle input...

I often regulate the A/C engagement on the highway if I'm going up hill or downhill -- which still requires throttle input.

Perhaps it can be TPS-related (i.e. < 18% throttle = A/C engage). It would have to be a precise mechanical placement or hacking into the TPS output, determining the voltage, and running a relay of some sort. Maybe a potentiometer could be involved to adjust the setting instead of a fixed output trigger.

Note: I don't have much electronics experience, so this is pure brainstorming (implementation would require assistance from others :o)

EDIT (follow-up question): Are the fans generally required if you're at highway speeds without a grille block? It would help to shut those down at cruise...

RH77