Why does power steering fluid damage the alternator?

[jagman]

I changed the high pressure PS hose in my 720  because of a leak that was spraying fluid all over the engine compartment.  Two weeks later I began to notice that the alternator was not putting out the voltage to keep the battery charged.  Today I removed the alternator and took it to the shop that rebuilds them and asked about whether the power steering fluid bath would have any effect on the alternator functioning.  They told me that it damages them in just a short time.   I have never heard of that. What is in the power steering fluid that does this?

[thisismatt]

Probably any oil/grease getting on the carbon brushes and commutator mucks them up

[datzenmike]

This!!! My first thought also. Change them or sand them and polish the copper ring contacts.