So, I was On a road trip today, about 2.5 hr drive. I've never had any issues with my AC or heater, but this is the longest trip so far.

AC is nice and cold.

Blows strong...for about the first hour. Then slowly loses blower strength to the point that it doesn't blow at all. And switching from vent to floor to defrost does nothing. Turn e truck off and let it sit for a few minutes and it works again.


Seems like a vacuum issue to me, right? But when I've heard of vac line leaks, it seems the door defaults to the defrost.

What do you guys think? When I got home and started looking around, I found the blower unit freezing cold and wi condensation all over it.

 

The blower motor itself got weaker and weaker? Sounds like you have high resistance somewhere. The longer the blower runs the hotter it gets until the resistance is so high it just quits. Probably the blower motor itself, but it could also be the resistor or a bad ground.

 

The air through the vents gets weaker, but the blower is still going wide open. The sound coming from the blower never changes, and you can cycle through the blower speeds and it sounds normal (gets louder with higher speeds), just there is no air coming thru he vents.

 

Ahh I understand. It does sound like a vacuum leak causing a vent door to switch. Id have to look at a diagram to see which mode is controlled by vacuum though.

 

Couple of thoughts, does the a/c drain a lot of water after you turn off the truck? You could have an evaporator freezing up. The other thing might be the blend door might not be opening all the way, allowing the evaporator to freeze. The blend door is electric I believe, not vacuum.

 

I would check the freon in the system. As mentioned above, a freezing evaporator would restrict air flow and after thawing out, returns to normal. If freon levels are with in spec, it could be dirty and partially blocked.

 

sounds like blend door motor to me not bad to replace.