Apparently the dealer says one of my coils is faulty, anyone know how to test them?

 

It is tested thru the computer system of the car, need special software to do so. Take the dealer word, most of them don't lie. I read on another board someone tried testing one with a multimeter, but the meter didn't have high enought current readings for the pack. As a pack turns out a Zillion volts.

 

Thanks very much for the information. Any idea where to get cheap parts?

 

Try importec and autohaus websites. They were the cheapest for a C230.