R & C HYD u/s
OK then. L A/P is working as expected. If you are in the cruise, it might work without problem for a bit, but eventually and inevitably you will get an AMBER A/P wng. This means that the A/P is working but is finding it difficult to do its job. (Think Unsched Stab Trim again - it is trying to keep you at your flight level.) Then, when you want to either climb or descend you will almost certainly get an A/P disconnect. Why? Because the Stab Trim is not responding (R & C). Does that help?