How bad were they damaged?

As for causes , I’m not a turbo core expert , but they have the turbo core tool app by danfoss that allows you to do a number of tests.

My services call last week was for a turbo core that had starter faults and bearing issues…in the end, after running all those tests, what I found is of the bearing sensor plugs wasn’t very loose and after cleaning and tightening everything we’re able to do bearing calibrations and haven’t had a problem since then.

There are a few causes, depending on the dtc model.

Tts300 have carbon touch down bearings. Oil contamination causes wore drawing on the bearings. The carbon then pluggs up sensors and generallyakes a mess of things. The sjaft rotating at 25k rpm imparts a lot of energy to oil being flung off the shaft.

Unauthorized rotation is another big killer. If there is not suction iso valves, refrigerant migration backwards through the compressor spins the impeller on the touchdowns. This kills them rapidly. If yoi see a PR in compressor monitor above 1.
5 or so when compressor is idle its a good indicator of reverse rotation. Failed check valves can do this, as can failed staging valves.

Refrigerant migration due to running pumps with no demand…

Excessive e-stops due to flow issues.

There are lots of ways to murder a turbocor.

Bearing sensor cable failure is fairly common as well. Gotta keep em tight.

A quick and dirty test is to wiggle the sensor cable during calibration. If you get artifacts your cable is loose or failing.

Thank for all your advise and info.