Hey guys. So theres an issue with my 98 ram 1500 5.2L 4x4 automatic. The a/c and heat only blow out the defrost vents not matter what orientation the **** is in. I have read a lot on the internet but cant seem to figure it out. A lot of research suggest its the vacuum lines especially considering cruise control also isnt working. Today I poked around at it. I dont have a vacuum gauge or smoke machine so forgive my primitive method. I located the vacuum lines and unplugged them 1 by 1 at each joint and put my finger on the hose to check for suction. All seemed good. I then got to the vacuum actuator located above the gas peddle and unplugged that vacuum hose to check for suction. Suction was there but id say only 1/4 of what it was, at all the hoses in the engine bay. I turned the HVAC controls to the vent position and then manually compressed the actuator while the vehicle was running. Initially there was quite a bit of force required to compress the rod coming out of the actuator but this got easier the more i did it and eventually it held position and air blew out of the vents on their own. Once the vehicle was turned off or a different direction of air flow was selected it was back to blowing strictly out of the defrost vents no matter which orientation i put the **** in unless i went back and manually compressed the actuator. With all this said the actuator is getting vacuum to it but my question is it enough or does this sound like a different issue? Perhaps a bad actuator? Im a little lost on this issue being as im new to this system since no vehicle ive had has ever had issues in this area. Any advice would be greatly appreciated. Thank you.

 

Under your battery there's a cruise servo with a vaccum line connected by a rubber elbow. You'll see it has broken or cracked. Replace the vaccum line and all will be well. I replaced the whole vaccum line from the intake. Some only replace the end that's broke.

 

Both the cruise, and your vent selector are vacuum powered, so, you most certainly have a vacuum problem. You need to go thru the entire system, and check for leakage, or breaks. That includes the vacuum reservoir under the cowl......