I own a 2000 Ram 1500 Sport Package 5.9 L, I have two issues:

1. While driving with the AC on, i hear a pop and heat comes out. Sometimes it does it randomly, but mainly does this while I'm applying the brakes or slowing down. To get cold air, I have to turn the AC off and back on, which doesn't always work.

I tried researching the issue, but found nothing. Maybe relay switch, tensioner, or serpentine belt.

2. While accelerating 15 - 25% of throttle, i hear a loud scratching noise coming from engine. I did replace serpentine belt, but no resolve. Could it be the fan or tensioner, maybe its the cause of my AC problem.

Please let me know if you have any idea, thanks.

 

If you mean that the A/C stops blowing through the panel vents and instead blows through the heater/defroster ducts, then do a search on wild or crazy vents. This is a common problem that has been discussed many times before in here.

 

The A/C issue is common for your year vehicle. Do a search for "Wild Vents" and that will give you a lot to go on. It's a problem with the vents and vacuum under your dash. That noise may also be related to it.

 

Thanks for the responses. My issue isn't heat coming from dash / defroster, it just blasts heat from the ac vents (upon decelaration). But I'll try some of the diagnostics for treating wild vents, maybe that'll help me find a solution.

I'll post my resolution, if I find one, thanks again brothers

 

Please LMK if you find anything further. I just got a 2001 5.9l sport today and am having the exact same problem.

 

Well I just figured out now by just switching the ac fan from low to high rapidly, it jumps to heat. I then have to turn it off and put he fan on low and back on for it to work agan.

 

That is your panel for your heat/ac moving back and forth. You are having a wild vent issue but it is the "flapper" under the dash that is doing it. Review the wild vent thread and it will lead you to the fix for your problem.

 

Found the problem. The "flapper" is called a Blend Door. I'm not a technical nerd so I don't know what most parts actual names are.. But under the glove box, there's the heater core (I guess) and attached to it is a small black box, square shape, held on by two screws. It's a motor which turns a small black piece which switches ac to heat. That little black piece is a bad design and will crack, like mine did. Since I live in AZ, I just made sure it was rotated to ac and took off the black box and left it off so that it can't switch to heat. At leas until I order the part.

You probably won't understand my directions, so here's the website which fully explains everything and has pictures and a replacent part.

http://www.heatertreater.net/Dodge%20Ram%2095-02.htm

 

Yep that's what I was talking about the blend door. I couldn't thing of the name for it for the life of me. glad to see you found the problem and the solution.

 

Ya I'm glad it's fixed. Thanks for all the help, couldn't have done it without you.