This is sort of an extension on another thread I made.

I have a 2000 Dodge Dakota 3.9 with AC.

There is a rattling noise from the belt tensioner pulley ( when I look at it is rattling against itself) when I put the A/C on or heat on and put foot on brake while in gear or while accelerating after stop. Noise disappears when in Neutral or when A/C off / heat off.

I have yet to take the belt off, though I notice that if I pour water on the belt the noise goes away for a bit before returning.

Further, though not sure it has to do with anything; the temps are starting to get cold here and in the morning the belt squeals a bit before warming up.

I'm asking for help since I need to order parts in but I'm broke and would rather only order the park I need (say belt, or new tensioner...) than order a bunch to troubleshoot it. Any ideas? Thanks a ton in advance


Should also note, the sound isn't always continuous. If I sit there listening to it, it'll be subtle, than you can hear the fan from the AC kick on and the noise will start as the RPM's jump a little.

 

sounds like the clutch on your AC compressor. Mine was bad and yes it makes a bad noise. You have to replace the entire compressor, they don't sell individual parts. If you have a refridgerant guy, you can get off a little cheaper. Compressors are about $200.00 or so but easy to change once the refridgerant is out

 

Would that explain the rattle when the heat is on as well?

 

I tend to think you have a bad tensioner. When it's weak, it slips, binds, slips, binds, causing the chatter.

The a/c compressor is just putting a big load on it more likely increasing how often it slips.

The compressor can run in defrost mode too.

Replace both the belt and the tensioner.