I wrote > Is there enough of a round-trip resistance difference in a car > body when a door is open ? So, how many people went off to their car with a multimeter ? Oh, just me then There is a difference, but you're talking fractions of an ohm, which might not be dependable in various weather conditions -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist