Alternator belt and rotary compressor

[awolff280sl]

For those owners whose setup includes a rotary A/C compressor mounted above the alternator, I just wanted to share what learned changing out my alternator. When using the stock MB alternator belt that measures 905mm long, it was just about impossible to slide a long socket under the compressor and along the threaded rod to engage the 14mm nut on the belt tightening bracket. There just was not enough clearance under the compressor to get there. At PUB, Gernold suggested that I try a somewhat longer belt that would effectively lower the angle of the threaded rod and thus increase its clearance under the compressor. I used a NAPA (Gates) XL7355 which is 919mm long and it's perfect. Using a 14mm long socket on an extension, I can now tighten my alternator belt without too much trouble.

[geezer]

Andy,

Thanks for the tip.

[waqas]

I always thought the alternator belt was supposed to be 10x935... is it supposed to be 905?

With my 935 belt, I've never had trouble reaching the tensioner under either the old York or the new Sanden compressor. I suppose that correlates with your discovery.

[awolff280sl]

Waqas, the 905mm belt length is what I got from my local MB parts guy when I requested a belt for an alternator mounted in the original factory location, i.e. "low". I wonder if, and I suspect that, a longer belt may be used with the original York compressor with the alternator mounted above. And perhaps that belt measures 935 and that length was simply carried over when the Sanden was installed in your car. If that's the case, someone may have unintentionally avoided the trouble I went through until I finally got it right.

[waqas]

My alternator has always been installed below. I bought the car with the York compressor installed above (along with that ghastly bracket). When the York finally went kaput, I decided to upgrade to the rotary Sanden. Throughout all this, the alternator belt has stayed the same at 935mm. Your discovery has certainly convinced me to continue with what works.

I suppose all this just gives us more options. But it does beg the question: what dictates the exact length of a given belt, besides the ergonomics of installation?