Looked at some of my parts and cars I had today: - My 1974 does kick on the AC compressor for defrost - A 1977 I just parted out did kick the compressor on for defrost. It has a detent on the switch so that the compressor kicks on for defog and defrost. Never noticed that before.
Some (not me) would say this is untrue. Of course coming from you ...it's beleiveable. My comment was to say that the defog works more effecently with the compressor system. This is what the heck I was talking about. Thomas knows...although, I have also seen the compressor cycle in defrost mode on every car that I have serviced the system on, unless the system was low or there was a problem with a switch or something. I am not saying ALL cars are this way either. The best system in my opinion is one in which the compressor has a seperate shut off switch or button, like the Toyotas for instantance. But the compressor still cycles when it's in the defrost mode. It's called modern technology, works mo betta...
I agree with blu, I don't know why other than maybe the air is drier but the defrost seems to work better with a working A/C system. A car without A/C will clear the windshield with the heat/defrost system, but the A/C seems to keep it from fogging back over. I have had older cars without A/C that you had to keep the heat blowing on the windshield all the time in cold weather or it would fog up badly, but yes, it will clear it without the A/C stuff being hooked up.
Yes, it does work better with an A/C compressor. If you've ever got in your car to find the whole inside of the window covered in water droplets, you 'll know that it's hard to get rid of that without the help of dry air. Luckily, some areas of the country don't have as much problem with this...
