I bought a 2007 MMH roughly 6 months ago and I love it. There is one annoying problem I have with it and I was wondering if anyone had any luck with this.

I live in Wisconsin and I would like to find a way to keep my A/C from engaging when I move the climate control to full Defrost. It may be as simple as removing the fuse for the A/C, but I would also like to have my vehicle have the ability to run in full electric mode while in defrost.

My guess is that removing the fuse for the A/C would keep the A/C from engaging, but there is most likely a secondary sensor in the switch that lets the vehicle know when the air flow direction control is in on one of the “red” settings (Max AC, Defrost/Floor, Defrost).

In all of my past vehicles, keeping warm air blowing on the windshield has kept the windshield fog free and kept it from icing up. I pretty much left the climate control on defrost 99% of the time in winter. With the MMH, I don’t want to sacrifice my mileage by running the A/C pump when I don’t have to. Any help would be greatly appreciated.

 

This is a good idea BUT, I wouldn't remove the fuse for the A/C. The A/C also cools the battery and while you might think it wouldn't come on in the winter, would you want to forget sometime and oops cook your $8000 battery?

What we do know is that the system closes baffles, or doors to redirect the heat. Can we open the windshield baffles while in a different mode than Defrost? Is that "rewire" able? Anyone know?

 

Well, the A/C system is also used to cool the HV battery pack when needed. So, disabling it might not be a good idea, and might even be flagged by the computer as a failure. That, in turn, just might void your HV battery warranty.

Also, my Honda allows one to enable or disable the A/C with the windshield defog. I know from my experience, trying to run the defog without the A/C is totally useless. With the A/C, on a warm rainy day, the windshield clears up in under a minutes. Without the A/C, it never clears up.

 

Incidentally... I find in the winter time MOST of the time I can keep my windows clear without modifying anything by turning the heater system to A/C with the heat all the way up or to just heat and the windows will stay clear as well if its dry enough. In the first mode you are better off than defrost because the engine can shut off normally. By judicious use of those two settings I can eliminate some of the defrost losses. I still sometimes have to use defrost at first to get the window clear to start.

 

Thats true, during the summer/spring/fall. But in snowy conditions that A/C during the defrost is fairly redundant if you are pulling in outside air. So at least during the winter it would be a benefit.

 

Yes you can!!! the mode doors (the things that direct the blower to the different positions) are driven by vacuum. The default for no vacuum is defrost. all you have to do is disconect the vacuum source to the HVAC, the doors will default to defrost then run the vent system, turn the heat control to warm and wa la, defrost with no a/c.

 

I thought that was done with vacuum but wasn't sure. Two questions:

1) Where is that disconnection? is it easy to find? Maybe we could put an actuator in that could be controlled from inside the cab... i.e. close a valve on the HVAC so its "disconnected".

2) You'd want to plug the disconnected hose wouldn't you? I seem to remember my ford probe running like complete crap when they left the vacuum hose to the cruise control disconnected once (I also didn't have cruise control but I was more concerned with the darn thing stalling out all the time).

 

If it is cold enough to snow, then the system automatically turns the A/C off when in defog mode.

 

You're right... if its cold enough it does turn off, I'd forgotten that. however I wonder if there isn't a middle point in between where its pretty darn cold but not cold enough to shut off where it would be useful to be able to direct the heat to the window, without A/C effects.

I do completely agree that if its warm and rainy you tend to be screwed and just have to have the A/C on in defrost, but sometimes in those situations I've managed to get away with running the normal A/C setting with some heat and it works pretty well as long as you aren't sitting still too long.

 

I'll look on my 07 to find it and yes you would want to plug the vacuum source not the line going to the A/C control head. As far as being cold and shutting off the A/C automaticaly I live in Texas, central Texas we see snow every 6 or 7 years and it doesn't stick. Defrosters don't work here without the A/C, so I knew it was posible just didn't think it was practical.