ac working great but i had it on defrost now it wont change to anything else.Do i need to replace this whole dash switch??

 

Check all your vacuum lines, also look under the dash at the blend door.

 

A leak anywhere in the vacuum system causes the climate control to default to defrost.
Check under the hood in any area you were recently working for an accidentally disconnected hose.

 

Every post is about some A/C problems. Too bad Cummins come with a Dodge. Crap Chrysler a/c systems.

 

The same thing occured to me yesterday, defrost only, cannot turn the system off. Also lost my fan control, blows one speed only. Temperature control still operatative. You guys still think I should be looking for a vacuum leak? Thanks.

 

Easy to tell if you have a leak.
After running the engine let it sit for five minutes.
Disconnect any vacuum hose, if it doesn't hiss you have a leak.
A leakless system will hold vacuum for days if not weeks.

 

Found hose with leak in it all is well.

 

You have two seperate issues, vacuum leak/no vacuum, this is the reason for defrost only.
the fan speed is most likely because of a blown blower motor resister (under dash near fan motor) some have reported having soldered the broken coil, another reason for failure could be a Fan motor thats drawing too much current and popping the resistance coils in the resistor, or something to that effect.,

 

Mine just went to defrost but it would still turn off.

 

Tracked down my leak this weekend. It was in the plastic vacuum line above the AC accumulator/dryer. I cut both ends clean, inserted a small stainless steel tube and sealed the splice with RTV black. All is well. Thanks guys.

 

Agree...I'm fighting with mine also...And everything is darn expensive when dealing with AC...Including the cost of evuating the system and recharging just to find the problem..