Relay Switches and Diodes?

[katodevin 10+ year member]

I understand that I need a relay switch to run my two amps and two fans and some lights.

I've narrowed down my choices to:

30amp 12v relay SPST - pulls 160ma

10amp 12v mini relay SPDT - pulls 30ma

Is a 160ma pull from my HU too much? Should I opt for the 30ma pulling relay? Whats the diff between SPST and SPDT?

Last question... I know I should put on a diode, since when a relay switch turns off, it sends a backcurrent. What type/rating diode should I use? I noticed that many people don't mention the usage of a diode at all here, does the commonly used 30amp 12v relay from radio shack have a diode built in?

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[mokedaddy 5,000+ posts]

right here

http://www.priceinsanity.com/servlet/the-956416/METRA-BRL30-30-amp/Detail

spdt means single pull double throw just like a switch. spst is single pull single throw.

And you shouldnt need a diode either but if you do a one amp is fine.