n/o n/c starter kill

k im looking at the starter interrup relays... it looks like there is a diode... so my q's is do i have to put a diode in a n/o and n/c relay... here is the diagram https://www.the12volt.com/relays/page2.asp

In 8 years of installing I have never used a diode on a starter kill relay.

thanks its jus that diagram looked like there was a diode ... i was jus too lazy to hook a up  relay to my jump starter to test it... LOL!!!

The diode is only needed if you're controlling the relay with an electronic circuit that's sensitive to the voltage spike that happens when the relay is turned off. If the circuit isn't designed to handle it, the spike could damage it- A commercial product should be protected internally, but if you have any doubt about it, you can add the diode across the coil just to be sure.

The coil terminals on the relay, 85 and 86 are interchangeable as long as it doesn't have a built in diode. The diagram shown just has it the other way; either way is okay. The way to connect the diode is to make sure the striped cathode side always goes the the 12V side, so that it's reverse biased when the relay is energized. The diode only conducts when the voltage spike happens, and starts bringing the voltage up beyond 12V. Then the diode starts conducting and limits the voltage. If you get it backwards it'll definitely blow something, so just make sure it's right.