Heating the outside incoming airflow will, without exception, reduce the relative humidity of that airflow. Additionally warm airflow, even moist warm airflow across the interior surface of the windshield will, always, ALWAYS raise the temperature of the windshield interior surface, most reliable method or removing windshield interior fogging and keeping the interior windshield surface above dewpoint.

Whereas the issue of A/C being capable of dehumification of the incoming airflow is strictly a function of the climatic conditions of the moment, dewpoint of that incoming airflow, and the limitations, limited operating range of your A/C.

If your windshield is fogging over or beginning to fog over then ALWAYS raise the blower speed and air temperature to the defrost/defog/demist outflow FIRST. Then you may add the A/C capability, which, should by pure happenstance it actually work, will accelerate the clearing of the windshield.

But you will now have two functions sort of at odds with each other. The A/C will be at its most efficient at the dehumidification task working at the lowest possible blower speed. The ability to quickly heat the windshield, both to remove condensation and prevent additional condensing of mositure, is best accomplished at the HIGHEST blower speed.

 

The AC heat combo is BEST for warm, rainy days. With manual climate systems:

If the outside air temp is above 55 DegF-

1. Turn on the A/C
2. Put the system in recirc.
3. adjust the heat to achieve a comfortable temperature.

This will even dry out your clothes if you get wet from the rain!

 

Salsbr-

You are amazing! Great job! I am speechless *( and that doesn't happen often ).

I installed an LED that lights whenever the A/C compressor is on.
You may be surprised at just how often the compressor NEEDS to run for the battery. Even in 65'F ambient air, after about 10 minutes of stop and go city conditions, and your HV battery needs A/C.

I hope you have NOT bypassed the car's ability to turn on the A/C on it's own. Have you????

Cool button. Nice engineering.

Your "stock" button is the odd one. The second one you bought looks like mine, and all others I've seen in 2005's and 2006's.

-John

 

Hey gpsman1,

Thanks! It was fun to do. Nope, I have specifically not bypassed the car's control over the AC. I went to great pains to make sure I was just mimicking the control.

I've seen a couple of people mentioning that they opened the AC compressor relay circuit. I was just wondering the same thing you asked me, if that keeps the battery system from running the compressor. But I suppose the car would complain if it weren't able.

Really? My stock button is the odd one? Hmm. I like that one better!

I didn't expect to start a discussion on the relative merits of defrost without the AC. That said, I've already used it as I had hoped, and it worked great. It wasn't really humid, but being in the car and talking was enough to start fogging the windshield. A flick of the switch, and the problems were gone!

Clearly (no pun intended) if it is really humid then I will still need my AC.

-salsbr

 

Do you remember any of the info, you could share, about how you connected up the A/C compressor 'on' indicator LED. While I am still not sure I want to override the system, I would like to know when the A/C is actually running.

 

Salbr system will not override the PCM control of the A/C system. He modifies the input from the A/C dash switch and fools the computer into thinking you don't want the A/C on. The PCM still controls the compressor it just thinks its supposed to be off. He accomplishes his system electrically, mine would do it mechanically. Neither would affect the PCM control.