adding a diode to a relay

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=112401
Printed Date: July 19, 2025 at 3:58 AM

Topic: adding a diode to a relay

Posted By: jheaman
Subject: adding a diode to a relay
Date Posted: March 16, 2009 at 12:32 AM

I've read the page about installing a normally closed starter kill relay. When adding a diode it shows the anode (striped side) connecting to the 86 terminal and cathode to 85.

In the installation manual that came with my remote car starter is says,
"To activate the coil on this type of relay, make sure that the +12 volts trigger is on the same terminal of the
relay as the anode (+ or non striped side) side of the quenching/suppression diode, and that the negative
trigger is on the same terminal of the relay as the cathode (- or striped side) of the quenching/ suppression
diode."

Is it me or does that not make sense? Can someone please verify this. I don't want to install it wrong.

Replies:

Posted By: i am an idiot
Date Posted: March 16, 2009 at 6:47 AM

posted_image

We usually connect 86 and 87A to the key side of the starter wire. No need to look for a true ignition wire.

The red wire in the diagram is the ground. The info you posted appears to be backwards.

Posted By: jheaman
Date Posted: March 16, 2009 at 11:24 AM

Thanks. So just to be clear, I can split the key side of the starter wire to go to 86 and 87a?

Posted By: i am an idiot
Date Posted: March 16, 2009 at 11:58 AM

Correct

Posted By: jheaman
Date Posted: March 16, 2009 at 10:28 PM

Thanks a lot! I also found this post.

https://www.the12volt.com/installbay/forum_posts.asp~TID~86348~PN~1~TPN~1

Someone posted the exact quote that's in my installation manual and also confirmed that the information was backwards.

For anyone who's interested. This is for a Prostart remote car starter, model CT-3471