New here so I have searched through most of the threads with AC problems and haven't seen a possible cause to this problem: 1999 Ram V6 3.9 - AC works fine in both MaxAir and Normal until I speed up or go up a hill that requires more power to stay at same speed, then the blower motor keeps running, I can hear it but the air stops coming out the vents. When back to cruising speed, air comes back through vents. The AC compressor stays running and stays cold. What could possibly cause this. Vacuum leak? If so where would I look?

 

Check the vacuum hose under the battery tray. I bet that's the culprit. If that is not it check all you vacuum lines. The one under the battery tray is a common one though.

 

I can't remember the loose term used on this forum, but basically the air flow isn't stopping but it's switching to a different vent like the floor or defrost and it's because of the above mentioned vacuum leak that doesn't really affect the system until the engine is under load.

Start checking all the vacuum connections and check valves. A common culprit is a visibly good connection but it's actually cracked and loose on the inside of the hose. Just cut .25" off the end of the line and put it back.

The check valves can be checked by sucking on both ends. You'll get suction on one but not the other. Hence check valve. If you get suction both ways, the valve is bad.

 

Thanks Billcart and Sooper, looked but didn't see any hose under the battery tray but am going to pull the battery and tray completely out to look. Checked the hose that comes from the right side of the throttle body, not a tight fit so will replace that and followed it to where it splits and goes into the dash, that looks good but will need to find it under the dash. Oh boy, fun time..

 

Before tearing into the dash. https://dodgeforum.com/forum/2nd-gen...ild-vents.html

 

+1 on wild vents......

 

Thanks zman17, read through the entire thread. Had no idea that the PCV valve could effect the damper doors for the vents. I checked the PCV by pulling it out and shaking it to see if it is free and it seems to be OK, alson checked the two check valves and they are working right. I did notice when I pulled the hose off the valve going to the dash that it had a vacuum on it. Heard the swish of it releasing the pull. I don't know it it should have had a vacuum on it after the truck sitting all night but guess that shows no leaks under the dash. Going to replace the rubber after the 2d check valve at the mainfold, it was loose fitting, so maybe that will be it. Will post results when I get er done.

 

Don't forget to check the line to/ and at the cruise control servo, as was mention earlier. Does the CC work?

 

Do not have Cruise Control on it.