Good Morning From Detroit,and its strarting to get cold up here,I have a 2000 2500 4x4 CTD,my heater control is stuck in defrost mode,hot -cold temp seems to work but the mode to change to heat,vent,defrost,will not work,possible vacuum valve?

 

possibly one of your vacuum actuators under your dash. i had this problem on my '97. look under your dash abover your brake pedals, and if you are familiar with what the actuator looks like, you will see it.

 

This is usually the result of the vacume actuator going bad. The defult mode is to stay in defrost. To get to it, you remove the plastic dash cover under the steering wheel. Remove the metal dash brace, rigth under the steering wheel. As you look at the firewall under the steering wheel, you will see the HVAC control duct. On the left side, there will be a small metal vacume actuator (silver in color). There is a vacume line attached to it, and it is held by two screews. Remove it, and install the new one.
I have replaced mine three times so far. The part number is 4720279AB ACTUATO71-C it list for 41.20 and I bought it for 34.35. Good luck

 

Thanks Fellas,I was under the dash yesterday and did see a vacuum actuator,3 time failure on yours y-not,sounds like the problem with mine,thanks again,have a Happy Thanksgiving,I am heading on a 7 day cruise to Mexico for the holiday week so I will mess with this when I return.

 

Mine acted up the same way,started searching and found out it was just the **** had stripped inside itself,hope this is yours too,cause it is a easy fix, new ****,goodluck Rick

 

Dresser Dave, I'm having the same trouble here in upstate NY and my toes are getting cold too. What ended up being the problem for you, actuator or contol ****?

Thanks

Steve

 

You have probably checked, but twice now my selector switch has broken so that the **** slips on the shaft...nothing changes.

Just a suggestion.

 

Well, after eliminating all other possible causes (acuators and control ****), it had to be a vaccum leak. The leak was just where the line comes out of the firewall high on the passenger's side. It had rubbed a hole in itself from resting on another metal part. I clipped the line below the leak and removed it up to the elbow fitting and replaced it with rubber hose. I intend to replace the plastic line that runs across the top of the firewall with rubber too. The plastic lines are cheap and very brittle.

Hope this helps anyone with similar troubles.

Steve

 

Thanks Steve,finally got a chance to look at the plastic line that runs along heater core pipes,and yes a hole was wore through,cut the pipe and attached elbow and now feet are warm again,thanks everyone for their imput,and Merry Christmas to ya all

 

I know this thread is old but it just saved my butt from taking my truck to the *******. I was driving home yesterday from work, and it was 99 out so I turned on the A/C only to find it only comming out the defrost on any setting. I was afraid the windsheild was so hot from sitting in the sun all day was going to crack. I found a hole rubbed about 2 inches away from the elbo under the dash. Cut it back pluged it in and all my settings work! Thanks guys.......