Adding relays to ground switched vehicle

Bretthn

Explorer
I have searched and searched several months now trying to find out how to add some relays to my lx470 which is ground switched. The best I have found is that when wireing the relay.
Normal relay wiring would have +positive power from switch going to 86, constant ground going to 85, +power direct from battery going to 30, and 87 would be +power out to accessory which has constant ground....

For ground switching I am hoping I understand this correctly:
I would have switched ground going to 86, constant +positive going to 85, ground direct from battery going to 30, and 87 would be ground out to accessory which has constant power?

or possibly

I would have switched ground going to 86, constant +positive going to 85, +power direct from battery going to 30, and 87 would be +power out to accessory which has constant ground?

All help is appreciated and I really am not as simple minded as this post may lead you to believe.

Once I can figure out the ground switching relay. I intend to
  • rear work light on a spdt switch with on with reverse lights, constant on, and off
  • all forward facing offroad lights relayed to only be switched on with high beams
  • rock/puddle lights relayed off of leftover wiring from facory step lights, on a spdt switch with on when any door opens, constant on, and off
Thanks in advance
 

4RunAmok

Explorer
On a relay, pins 85 and 86 get connected to your switched source and a ground, it doesn't matter which one, since what you are powering is a coil inside the relay, which when powered magnetizes and pulls the relay.

Normally, you would run an inline fused wire from, for example, a wire under the steering column or fuse block that goes hot when you turn on the key, to pin 86 and pin 85 to ground.

In your situation, you want to run a constant hot wire from the battery (fused within 18" of the battery or fuse block) directly to the relay pin 86, pin 85 will go to your switching ground source. Constant power will be sitting at pin 86 until pin 85 finds ground, thus charging the coil, connecting pins 30 and 87. Remember to cap 87a (center pin), since the power from 30 is directed to 87a until the relay clicks. (30 and 87a = Normally closed side, 30 and 87 = normally open side.)

The FIRST diagram in the link you provided is just fine.
 
Last edited:

screwball48

Explorer
A lot of individuals use the HID installation plugs for the headlights so that you do not need to splice the factory wiring when you install aftermarket driving lights.


Sent from my iPhone, just ignore all errors because the phone did it.
 

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