Interchangeable relay/reading help

[GostRidr]

I'm chasing down a headlight issue in another post and am trying to learn about relays. Am I reading the pic on the relay correctly? It seems the pics on my relays for G1 G12 and the headlight motor are the same. Are these all interchangeable or do I have the wrong one somewhere?

Also, can somebody direct me to a basic 101 relay tutorial as I will do much better once I understand the significance of 87 87a 30....

Thanks!

[bell]

lots of good general info here.......
Single Pole Double Throw (SPDT), Single Pole Single Throw (SPST) Automotive Relays

[GostRidr]

Bell, GREAT website. It looks like I will be ordering a book they recommend as well. For my money, it seems electrical issues are by far the number one overall thing we will face keeping these beauties on the road.

That being said, can anyone jumpstart my learning here? I know that G1 and G12 are interchangeable. The pictures match the one from the headlight relay with one small exception. I can't tell if it is an electrical difference or just a picture difference. The 'box' between contacts 85 and 86 is one piece on the headlight relay and two pieces on the G1/G12. Probably a difference but I want to confirm.

Thanks for the help!