I belong to a tractor forum: MyTractorForum
billed as The Friendliest Tractor Forum and Best Place for Tractor Information.
There are several threads there well presented and with good pictures. This one deals with using a digital multimeter to check out a car's electrical system.
Link: MyTractorForum

- The Friendliest Tractor Forum and Best Place for Tractor Information > TECH Exchange > Articles - Bodywork & Electrical
Top Ten Multimeter Tests - Part 1 of 2