i am new to dodge rams. i have a 2001 ram 1500 laramie with 5.9 magnum. i have pulled the ac down,fixed leak and got it blowing cold,but it gets colder only when moving. sitting at a stop it blows cold,ut not as near as cold as when moving. my coolant level is just above minimun on reservoir when cold so im thinking its needs to be filled to max line, now here is my problem. ac blowing good and one min i hit my brakes and it thumps and goes hot ,turn off and back on got my cold back, but sometimes that stays cold but then i lose ac to defrost when accelerating. i know it has to be a vacuum leak causing both problems. does anyone have any idea where to look first so i dont have to trace down the whole system.

 

You have a selection of problems there.

Coolant level. There is a "full cold" line, and a "full hot" line. Don't overfill, it makes a mess.

Possible failing fan clutch. (a/c works good when moving, not so much when sitting.)

Blend door issue. Your truck has a little stepper motor under the heater box, just above the passenger side of the trans tunnel. The coupler between the motor, and the axle, cracks, so the door can flop freely. Two screws and an electrical connector to pull it and check. (the screw toward the firewall can be a pain.)

Vents switching IS a vacuum problem. There are a couple checkvalves you can install to solve it. (search the faq/diy section for "wild vents".)

 

I looked on overflow bottle and there isn't anything for cold or hot, just min and max lines and thats all.
I was already thinking of doing the heater treaters fix. Fan clutch could possibly be weak. 217,000 miles. I hear the thump on driver side so think maybe hose on accuator by gas petal could have a vacuum leak

 

Check your overflow bottle when the engine is fully warmed. If it's still low, add a little.

Fix the other stuff that you know is an issue, then see what's left.

 

The sound you are hearing is the blend door slapping the stop inside the a/c box, mine did it .....I could step hard on the brakes and it would go hot, try this , get in a parking lo or some where safe to do this, and when its blowing hot, from a stop accelerate hard , you will feel the a/c get cold, try not to step on the brake hard and drive around a little it will be cold only when you step on the brake a little harder will it move the door,
The problem is fixed by replacing the blend door actuator connecting piece to the blend door,its called an INTERPOSER
to fix it you have to look under the passenger side at the a/c heater box, near the trans tunnel at the bottom, there is the blend door actuator, there is only one screw that is a pain to remove, if you pull the carpet back and the padding you can remove the screws , a flexible shaft with phillips bit on end helps or my favorite sears craftsman right angle philips screwdriver, that one really works, remove the screws and pull straight down, it is real tight under there, move out of the way, look and you will see a small usually black piece of sticking down, you have to pull that straight down, some are real easy and fall out others i have done not so easy, any way the original part is available from chrysler for about $12.00 or you can get a better one from heater treater go to there website you can see pictures, it is metal. the only thing you have to do is re install it and put the actuator back up.
I have seen people remove the screws all but the last hard one pull down and the actuator will turn out of the way with the HARD screw still attached, its up to you, good luck.