Defroster re-wire?
 

My wife can't seem to drive the car without the defroster on.
I note that the a/c can run on regular and still allow the motor to shut down at the stopsigns, but that the defroster asks for max a/c, and so cannot allow the motor to shut down.

Has anyone explored the possiblity of haveing the defroster work with regular a/c?

MM

Re: Defroster re-wire?
 

I have thought about the same issue, and although I haven't done anything yet, that's just a matter of time.

There is an AC request wire from the controls to the compressor. I was going to remove this line, and attach it to a switch. Then I would have control of the AC no matter which position the air was in. I know there is such a wire, but haven't bought the shop manual necessary to complete any design.

FWIW.

Re: Defroster re-wire?
 

Right. We could put an ancillary switch to interrupt the feed to the a/c clutch.
I haven't looked, but I imagine one can find that one at the the compressor.
What I want to do is install a switch to be able to opt between calling for max A/C and regular A/C when defrost is selected.

MM

Re: Defroster re-wire?
 

I would LOVE to have this option, and have thought about a "hack" for sometime.
I probably won't get around to it until next Fall though!

I live in a very dry, but cold winter climate.
Often there is light frost on the glass, but the humidity is below 30%.
I need heat only, not the drying effect of the A/C.

PLEASE! Keep us posted if someone finds an easy work-around.

-John

Re: Defroster re-wire?
 

Keep in mind that federal law requires that the climate control systems be designed so that the A/C compressor runs when in defrost mode. It's required for safety. You need a clear windshield to be able to see to drive.

I have always personally preferred to have a manual cutoff switch for the A/C compressor and some cars I have owned in the past have had them. But, because of the the legal requirements I mentioned, even those systems were wired so that defrost operation bypasses or ignores the cutoff switches. In a non hybrid vehicle, adding a switch to the circuit going to the compressor clutch would allow you to disable the A/C compressor and save some gas.

In the FEH I think it would not be so simple. When you select the defrost mode the system not only turns the comressor on but I am quite confident that the control system would have to suspend the engine shutoff feature (as it does with Max A/C) which is so integral to the operation of a full hybrid. Simply disabling the compressor probably would not turn the engine off.

Just my two cents. And BTW. For those who think the Prius has an advantage because it's compressor is powered by an electric motor remember what many physics professors have said for years. There is no free lunch. In other words it takes energy to run the A/C compressor regardless of how it is driven.

Re: Defroster re-wire?
 

You know how you have two A/C settings on the Escape, and one of them is marked red on the dial, but the OTHER one is not? I wan't to use THAT compressor setting when I have the defrost on. That way, the engine can still cease at a stop sign while the defrost is on...

Re: Defroster re-wire?
 

Oh yeah????? What about base models with no A/C????

THEY get to drive with defroster heat only, no A/C.

Re: Defroster re-wire?
 

z1rider - can you provide a reference to this law? I searched and couldn't find any reference to it.

Re: Defroster re-wire?
 

There is no such law requiring A/C be combined with defrost heat. I have a 2005 Scion xB that has a button to disable the AC Compressor.

De-humidification as a result of running the compressor is a nice to have, not a have to have. On the FEH, to pick and choose would add a level of complexity to the computer program. Worse yet, imagine going into EV mode and having the windows instantly fog up under certain conditions.