I am confused as to what you would like to achieve.

When on a highway, you probably are running the ICE full time. So, it isn't like the A/C is making the ICE run when you could, instead, be in EV mode.

Temperature alone should be cycling the compressor on and off while driving. IMHO, cycling the A/C 'on' and 'off' based on temperature is better cycling it 'on' and 'off' based on just a time interval, no?

 

On a 90 deg day in Texas the A/C hardly ever cycles, but the inside of the vehical will get a little colder than I like on the highway. The A/C consummes about 2 mpg so if I could cycle it to raise the temp I could save maybe 1 mpg.

 

I think the same compressor control wires you used in the A/C control panel. An on off analog switch and a potentiometer to control the on time and one to control the off time. these trims don't have to be externally adjustable for now. I could probably muddle my way through a circuit design using an old 555 timer,caps and resistors but I would have to re teach myself all the things I forgot 15 years ago when I dabbled in electronics. What I need from you is a circuit design and parts recomendation I can do the rest. Like I said similar to a wiper delay system. Yoour A/C switch was very well done BTW

 

Of course the overblown thing to do would be to wire up a temperature controler and tada... we've added climate control to the FEH (pre 08 of course).

 

Not to much more trouble. My dad did this to our 67 Olds Delta 88 (tank with a 425 cid engine) He was trying to get better than 9 mpg (when gas was $.23 A GALLON) he rigged up a thermostat to the compressor to cycle it because it didnt cycle, just blended hot air. It did improve the mileage enough that he used it all the time.

 

I still don't get the objective.

Why not simply raise the temp directly, instead of indirectly by a time based cycling.

BTW, do car A/C units have minimal 'off' times like home A/C units do? I know my electronic thermostat has a built-in protection to keep me from manually causing a too short off cycle.

 

Today's A/C are cycled.

I don't know about the hybrid, but I know that on my Mustang, stomping the gas to the floor will also force the A/C temporarily off. I guess my point is that the computer is in active control, always.

 

You don't understand how automotive A/C systems work. They DO NOT cycle to regulate the inside temp, they blend heater air in with the A/C air to warm the cabin. When you turn the cold/warm **** you are moving a cable that opens a door to blend heater air into the air coming from the evaporator. In fact if you had the A/C on and the temp all the way to hot the temp would be warm and the compressor would also be on. The reason your Mustang cut the A/C was for power and to prevent overspeed of the compressor. The compressor will cycle only when the low side pressure drops below 29 psi or the evaporator temp sensor detects freezing condition.

WALT I'M NOT FEELING WELL SO EXCUSE MEFOR YELL'N AND ATTITUDE.

 

Mark, Forgive me, but it does really sound to me that you are going though a lot of effort, for no advantage.

Are you saying that your car gets too cold with the A/C on the lowest blower speed? Then why not turn it off, and try vent at highest blower speed?

I promise you, at a low blower speed, your A/C clutch is off a greater % of the time than it is on. For me, at blower speed 1, the A/C is on for 10-15 seconds, then it is off for 45 seconds. Repeat.

Even on blower speed 4, the highest, even on "MAX AC" setting, it still cycles, just the reverse... 45 seconds on, 15 seconds off.

The car already does what you want it to do.
Keep it to the white A/C position, and the A/C won't run at all in EV.

Now, I really want to make the mod for hot air only to defrost, as Colorado has pretty dry air to begin with. It can rain here at 40% Relative Humidity!
And I've seen it snow at 42 degrees!
( Obviously the clouds are colder / wetter but where I drive it isn't! )

And on top of that, I really want EV in defrost mode.
That is the larger objective.
-John

 

I think our differences are location. On a 90 deg day our humidity can be as high as 80% I need the air flow out of the vents on the highway but that will keep the compressor on all the time, yes I have checked this, again you are at a higher altitude. So I want to cycle the compressor. Another thing is the defoster around here won't work without the A/C on( humidity 100% at 50-70 deg), at least part time, again a reason to cycle the ac, but a cycled a/c defroster will be a little more tricky.