Truck is an 03 with the 7.3L.

I posted on the 7.3L forum, but haven't got any answers, so I thought I would try my luck here.

Last week I noticed the A/C indicator would turn on when I switched from defrost to defrost and floor setting. Does not do this when changing from defrost to any other setting. I have never notcied this before, is this normal? Below is some back ground information.

Recently we have been hammered with snowfall and I have had to use my 4x4 daily. The truck has had a vacuum leak at both hubs and I have always manually locked the hubs for the 4x4 to work. The vacuum pump has been running alot lately so decided to check for leaks. I capped off both lines to the hubs, since I new they leaked. That took care of the heater defaulting to defrost when in 4x4. The vacuum solenoid seems to work properly and so does the heating system. I can hear the blend door working. After the truck sits the vacuum pump turns on at start up, it has never done that until recently. Somewhere the vacuum is bleeding off. I am suspecting its somewhere in the heating system since the hub lines are capped. Would a vacuum leak cause the A/C turn on when switching from defrost to defrost and floor?

Any help would be appreciated. I have read through many posts, but nothing like this has bee nmentioned before.

Thanks

 

I do remember reading that it does defaualt when in vacuum leak. I dont recall what post, but you definately have a leak from what I have read, there was a post about how to narrow down where the source of the leak is, i will see if i can locate it.......but I would say that it is a leak which diagnosis it, unfortunatly where the leak is is another story...

 

Thats what I figured, its prbably under the dash somewhere.

 

It is normal for the A/C compressor to run in defrost mode in most cars. Ours just has a light confirming it. You can turn the compressor off if you want...I do unless I have the whole clan in the car with me.

I have never researched why the compressor comes on but I suspect it has something to do with removing humidity from the air so it doesn't remain in the interior of your vehicle only to fog up the windows again.

Stew

 

For some reason this morning the A/C light did not come on when switching from defrost to defrost/floor setting.

Maybe I am over analyzing this.

 

I thought I would revive my old post and clear up what I was previously asking.

Is the Climate Control System default setting to turn on the A/C compressor when the defrost/floor setting is chosen, auto on button or the fan speed button is pressed (the A/C kicks on via the fan speed button only when the system is previously off.

I just want to know if this is normal or attributed to a vacuum leak.