SALSBR:

Almost all modern day vehicles have the ability for the engine control ECU to disable the A/C should the engine water jacket begin to overheat and/or if the driver uses WOT to rapidly accelerate.

So the climate control ECU sends the signal to engage the A/C compressor clutch to the engine ECU and then the engine ECU decides if the clutch should be engaged.

Find the wire that carries this signal to the engine ECU, open it, and the ICE will not start when the climate control ECU A/C "on" signal indicates a need for compressor activation.

 

I haven't experienced this yet (today's temperature in Phx 77 deg). Sorry I had to gloat after pretty continuous AC use this summer in the new FEH. We are in the middle of the good times to have a hybrid here.

 

Ditto, more or less.

I'll admit, it never occured to me to run the non-red AC with the setting at hot. I'll give that a try.

 

Actually there are two wires in this system, and they go directly from the function switch of the climate control. In essence I am planning on unplugging these wires, and inserting my own control over them. The difficulty is only in making this something convenient to use that doesn't ugly up my interior.

 

You're misunderstanding, the signal wire, single wire, I'm proposing goes from the climate control ECU/Module to the engine control module. In my case I used a miniture "rocker" type switch "hidden" by mounting it on the bottom of the dash panel just a tad beyond my left knee.

 

Ok, you are right. I must be misunderstanding. The Escape AC is governed by several control lines. One forces the ICE on, a second only runs the AC when the ICE is already on. There are others, but these are the ones I care about.

Sure I could just connect the one wire to a switch, but my plans are far more grandiose.

I am adding a switch to the dash where there is a blank now. For this purpose I bought a replacement Rear Window Defrost switch, and have removed the Rear Window Defrost graphic on the face of the switch, and will paint on my own AC indicator so I can see it at night. I will replace the Rear Window Defrost On indicator with a two color LED and will display green for the green mode of AC, and red for the ICE on AC.


There are easier ways to do this, but this way meets my user interface requirements.

I am documenting this process, and will post the entire process when I have completed it. That is likely to be early next year at the rate I am going.

 

Hi,

The problem with this option is that there is little to no airdlow through the vents below the windshield. The only way to get air through those is to turn on the defroster (AFAIK).

Cheers,

rcomeau

 

Sorry, you need to start thinking "outside the box".

Outside the climate control "box"/module/ECU, that is.

I cannot say for sure about the FEH/MMH but in our Prius there is only one signal wire going from the climate control "box"/module/ECU to the ICE control "box"/module/ECU.

If the climate control "ECU" commands an A/C compressor "ON" signal to the ICE control "ECU" it is the ICE's controlling "ECU" that must "know" to start the engine (or not, if its already running) before energizing the A/C compressor clutch.

Yes, adding a LED or two for indication of switch position is not a bad idea, but I would stop with a single red one to indicate that the A/C is disabled and the system is thereby always in heating (RED!) mode.

While you're in there, in the climate control module, you might want to see what you can do, modify, to force the system into HIGH heaqt mode when you activate the 3D, defrost/demist/defog, function. In my 92 LS400 I have a simple rocker "toggle" switch mounted under the dash that adds a resistance in series with the IAT thermister. Before I activate 3D mode I flip this switch, the climate control ECU "thinks" the passenger cabin has suddenly grown VERY cold, and so it raises the blower speed to maximum while at the same time swinging the reheat/remix door/vane to the maximum heating position.

I wasn't successful with this mod in later Lexus model years (2000 GS300, 2000 AWD RX300, and now a 2001 AWD RX300) since some level of digital signal processing had been added to the IAT sensor signal to avoid transient "out of tolerance" readings. So my "quick switch" to force the system into maximum heating mode no longer works, it now takes 2-3 minutes.

Luckily turning the blower speed and the heating level up manually is a lot simpler and quicker in my 2001 AWD RX300 than in the 92

 

Just a question with all these modifications. The A/C compressor is the same one that serves the battery in the back. Are any of your mods going to interfer with the compressor kicking on to cool the battery when necessary? If they are then I'd be worried about toasting the battery pack in high heat. Or are the controls separate enough that you can set up the wiring to only prevent A/C activation from the internal climate controls.

 

The mods I am talking about will have no effect on the battery cooling. I am only talking about removing connections from one switch, and putting them on another. These controls are only for the interior only.

But your point is well taken, and I will double check before I actually mod anything.