Originally Posted by dwightdmagee
Not sure where the actual meter is. I'm not very sharp on electrical jargon, but the thing is called a potenziometer, or something like that. The oil itself will not conduct electricity (that's why it is used as an insulator in transformers), but when contaminated, the dirty oil does show an electrical potential across the supply sample. This potential reading is what the ECU will use to constantly update the life left in the oil until due for a change.
1) In 28 years doing component-level electronic repair, never heard of a
potenziometer. A
potentiometer is a variable resister, like a volume control.
2) Oil is not used as an insulator in transformers, it's used as a heat sink. Filling the cavity with oil allows heat to flow more freely from the core and windings (where it is generated) to the outer casting's cooling fins.
Now, it IS true that oil is a very poor conductor of electricity (otherwise, it would NOT be in a transformer- so you got that one right).
And I am unsure about how well we could measure the change in resistance with contamination. Can't say I'v read anything in the manual about this, the book implies that the light is turned on based on miles and time, only.
Not being a smartass, but had to comment. Now I'm gonnna go see if I can find anything on resistance changes with contamination.