relay advice for newby

85 NEG is the proper convention, you'll still need another diode to prevent feedback, the relay built in diode is a quenching relay to prevent the 200 volt spike flashing back to your circuitry when the relay is switched off. Light bulb via 1N4004, band away from bulb to 86. Ground to 85, power fused 10amps to 87, output to extra bulbs from 30. For indicators you will need extra circuitry and relays (2).

There are no -ve or +ve relays. (Excluding solid state etc...) I suggest you buy all relays as SPDT (aka 5 pin) assuming they are the same price as SPST (4 pin), and add your own 1N4004 or 1N4007 diodes if required.

I think you guys are trying to confuse me. My objective here is to supply one 12v brake signal to my Tekonsha brake controller which triggers my blue wire and subsequently, the electric trailer brakes. It is only in the last 18 hours that I ever even saw a picture of a diode, much less soldered one. I cannot attach diodes to bulbs and screw up a very expensive tail light converter/wiring setup I had to buy to overcome the Can bus and my LED tail lights and still have trailer lights. I understand how relays function and I know now what a diode does. I need to know if the 85 negative relay I referenced in the OP will suffice in providing adequate protection from the anticipated current spike.

Yes but VOLTAGE spike not current that's what the built in diode is for.

In that case buy the relays with inbuilt spike quenching diodes. Just make sure 86 is always the more +ve compared to 85. Whether you ground 85 or supply +12V to 86 does not matter.    But again, ensure that ~13V BCM output can supply the extra current for the relay coil. (If using the BCM output and not brake lights etc.)

No stick to ISO conventions, 30 = power, 31 = ground, 56 = lighting etc. etc. When you're doing dozens per week like me, keep everything the same.

howie ll wrote: Yes but VOLTAGE spike ...

Correct, I meant voltage spike. In my original post I identified a place that sells them online. Does my local Radio Shack sell something like this or do I have to do the online?

Yes but without the diodes.

Thank you all for your help and for generously sharing your vast knowledge. You cleared up many issues for me and I wish I could contribute more to the forum. I will be going forward with this and I'll try to remember to advise of the outcome. Maybe we'll talk again when I put in my backup camera and monitor.