Mini-ISO Relays

Uh, Relays?

The Basic Car Audio Electronics site has a very good explanation of how relays work.

Mini-ISO

30-amp Mini-ISO relay with pre-wired single and double sockets

The most commonly found aftermarket relays are Mini-ISO relays, typically referred to as "Bosch-type". There are many brands available, including Bosch, Hella, and whatever no-name brand your local Kragen stocks. To my knowledge, none of the available relays are fully sealed. The bottom panels appear solid, but there is no epoxy applied where the terminals enter the body, so ultimately there is a path for moisture. If you want a 100% sealed relay, look at these.

Sockets

Relay sockets make it much easier to change out a bad relay. Without a socket, you'll have to remember which wire went to which terminal pin. Relays are generally extremely reliable, but if you're trying to track down an electrical gremlin the last thing you want to do is fiddle with such a headache.

Tessco sells supposedly genuine Bosch sockets:

• $0.80 for sockets with mounting tab (p/n 465687).
• $0.45 for sockets without mounting tab (p/n 464695).

Neither of these come with the metal terminal inserts, those are sold separately (p/n 91211, 100 pack, $22.25!). Alternatively, pre-wired sockets are available for $2.10, but you can't get these with a mounting tab.