Chamberlain HD900D help

[T56 Impala]

Hey folks. Got an issue. Diagnostics say my RPM sensor is bad in the title listed unit. I've looked on line and can't find a diagram that shows it or a part number for it. Anyone know how to replace one of the sensors? Where it's located? How hard the repair is? Ever do it and is it worth the trouble?

Thanks!

 

[pattenp]

I believe the rpm sensor is part of the motor assembly. See page 41.

http://www.chamberlain.com/CatalogResourcesV3/en-us/shared/files/tucmanuals/114A4267.pdf