I’m trying to find the source of a weird grind/rattle noise I hear whenever the ac is on in my 68 Coupe with a 302, T-5, and old air ac. Here’s the thing, it only does it when I’m at a dead stop at a light and I engage the clutch in first to get rolling. Once I’m on my way, all is good. I feel like the noise is rpm related, meaning that the initial slow move from a stop to go where the Rpms aren’t too high maybe don’t turn the compressor fast enough? Or the belt is slipping? Anyone experience something like this?