2003 dodge 1500 conv/5.9 as of today, while cruising down the hwy with the ac on it started switching from the ac vent to the defroster vent and down to the floor vents. This sequence lasted for about 10 minutes before reverting back to the ac vents? this kept happening over and over again.


any thoughts as to what would make this happen???????


thanks in advance

 

That's caused by a vacuum leak. In the absence of vacuum defrost is the default airflow direction. Since it only happens when the CC is on, there's a good change the CC vacuum servo is leaking.

 

First thing I'd do is give the various vacuum lines a quick looksy to see if there are obvious breaks/cracks. If nothing obvious is wrong, check the vacuum reservoir ball beneath the headlight. If you have a hand vacuum pump, test it to make sure it holds a vacuum. Make sure the hose connection to it is tight. If the hose to it was loose, water can also end up in there which may or may not affect it's performance. If that looks alright, then give the various vacuum hoses and saucer looking deals in the dash a closer inspection.

 

thanks for the reply, i'll be checking all the vacume lines this weekend.

 

the van isn't haunted lol. When i owned it just like every other dodge van i owned that happens when the a/c is on max.