bosch (and all german vehicle manufacturers who use bosch components) use a standardized method in their wiring to help with troubleshooting, design and layout. this particular relay is used in tens of thousands of different applications around the world and terminal 30 is universally used as main power in. it's the same as the way we mark stuff with + and - . if you look at any wiring schematic for any german vehicle "30" is ALWAYS battery voltage and 9 times out of 10, "15" is switched voltage. even though the relay will work with the wiring reversed it's just weird that HD chose to be the only manufacturer in the world to do it.
The key to problems is usually the ignition key.
Posted on May 2, 2012, 11:21 PM from IP address 220.127.116.11