Aux back up lights tied into tail lights with switch

I know enough about wiring to tap into the tail lights or wire up a dash switch but how would I go about taping into tail lights so the aux lights come on in reverse but also wire a dash switch so that I can turn them on when not in reverse? Probably pretty simply but if anyone can explain or better yet, provide diagram....

Thanks

 

Edit: previous post got deleted so here's what I did. Look at the 2nd gen mods thread and it will show you a few different spots to tap into for acc power, and where to tap into the reverse circuit. IIRC I used 1 add a fuse for the acc circuit and one quick splice into the reverse camera circuit (the wire that becomes hot when the truck is in reverse, that gives power to the camera - I did it this way because I did the anytime on camera mod at the same time), this makes it so both of the switch's incoming power wires are in the cab, and you only have one wire (outgoing from switch) that goes through the firewall. The added power draw for the existing circuits is 0.120 amps. The outgoing wire from the switch goes to the 86 pin on the relay. Relay pin 85 goes to ground. Then you add a fuse capable of the light's load, coming off the battery positive, to the 30 pin on the relay, 87 (not 87a) goes to the circuit. The relay I used is an SPST normally open Bosch Type.

OP, try this diagram. It's how I have mine set up, fuse tap from an in-cab, hot on ACC circuit, and a fuse tap from the reverse circuit, as power sources to a SPDT on-off-on toggle switch, with the common (output) going to the coil side (86 pin) (control) of the relay.

Fused 12v from the positive battery goes to the 30 pin on the relay, this is your power for the lights. Then the 87 pin goes to the positive on the lights.



What this will accomplish; Lights on w/reverse, lights off, or lights on when you want, depending on switch position. You also have very little current running into your cab and through your switch, and can therefore use smaller wire to carry the load, as it only needs to be enough to activate the relay, which can be mounted outside of the cab.

Let's say you've got two 55w aux lights you want to use. These lights will draw 9.16 amps (55 watts x 2= 110 watts. 110w/12v=9.16 amps). A relay is a switch controlled by a switch. The relay can generally handle a higher amperage load than a switch, and to activate the relay, it takes very little current (~0.120 amps).

If you do some searching, there are a TON of threads and info available on this.

 

X2

Only thing I'll add is I used the tail light circuit instead of wiring to constant hot. So I have the option of lights on in reverse, lights off all the time, lights on when I flip the switch BUT the tail lights have to be on. This makes sure I don't leave them on accidentally.

 

Mine is wired to be on with reverse or ACC, so the truck has to at least be in ACC (key in and turned) for the lights to be on. The only constant hot is the power to the relay. Tail light circuit would work as well, though, it would give you another fail-safe.

I will add that I have once left them on while driving, because I used a cheap non-lighted switch, so I don't have any indication they're on in the cab, unless I check, but normally it's in the REV position. I check regularly now to make sure they're off when I'm in drive, but soon that switch is gonna be changed to one with an "on" indicator light.

 

Yep, indicator light is on my list as well. I had it that way on my last truck, the Tacoma isn't as easy to put a light in, so I have left them on before.

 

thanks, that's just what I needed. just wastn't sure where to make the connection between the reverse power and the switched power.

 

Just to be clear, instead of grounding the in-cab SPST switch, I connect to the reverse circuit, right. So when switch is on, lights are on as long as the key is in ACC position or truck is running. When switch is off, I should get lights only when truck is in reverse. Would a SPDT switch be better?

i.e.
SPDT
up = lights on
neutral = lights off
down = lights on in reverse only

SPST
up = lights on
down = off except when in reverse

 

No, the spst switch will not work if you just hook the negative on the switch to a reverse circuit fuse tap.

The switch needs to be SPDT, both of the switches you described would be considered SPDT, but the first one is a 3 position (on-off-on) and the second one is a 2 position SPDT (on-on in rev).

The "negative" on an SPST switch is not for the circuit, it will only be present on the switch if there is an indicator light, and the negative is to complete the indicator light's circuit.

"Pole" refers to the number of separate circuits that a switch controls, "throw" refers to the number of positions the switch can have to complete the circuits.

A simple SPST switch, with no indicator lights would have 2 pins, one source (incoming + or -) and one load (outgoing, same polarity as source). In the "off" position, the first pin is disconnected from the second, turning the switch "on" connects the 2 pins' contacts. If it has an indicator light, it will have a 3rd pin, that gets grounded, and completes the circuit for the light when switch is in the on position.

A simple SPDT switch with no indicator lights, would have three pins. SPDT can have 2 or 3 positions. If it has to positions, both would be "on", so if pin 2 is your common pin, on a 2 position SPDT switch, then in position one, pin 1 would connect to pin 2 (p2 is disconnected from p3), and in position 2, pin 3 would connect to pin 2 (p2 is disconnected from p1).

If you have a 3 position SPDT, one of the positions would be off.
Position 1: P2 connects to P1
Position 2 (center/off): P2 is Disconnected from either P1 or P3.
Position 3: P2 is connected to P3.

 

Thank you for the detailed explaination Ryan. I think I get it now. I will report back after wiring (or attempting to wire) this up. Cold here in the north east for the next week or two so probably won't be actually attempting this until sometime in April.

 

Where under the kick panel? There are a ton of wires under there. I was going to tap into the reverse lights wire at the tail light but under the kick panel would be easier if I knew which wire.

 

Awesome - thanks

 

I haven't done this just yet - been doing some more research and I think I found what I want to do.

I plan to use a 5 pin relay with SPST switch in the cab. Relay pins 30 to battery positive terminal via fuse, pin 85 to ground, pin 87 to lights, pin 86 to in cab SPST switch, pin 87a to tap into reverse lights wire. In cab switch will be connected to fuse for power only when ignition in ACC position.

In cab switch in off position: relay coil unpowered - pin 30 and 87a connected. Result = lights on when in reverse.

In cab switch in on positon: relay coil powered - pin 30 and 87 connected. Result = lights on.

Key out of ignition = no lights whether switch is on or off.

 

Not quite. If you wire it the way you're describing, the lights will not come on with reverse, you will just be connecting the reverse light circuit to additional constant power.

87a and 87 are never ever connected (internally in the relay). With 30 as your 12v source, which is normal, you always have 12v going through 87a. When you put power to the coil, it switches from 87a to 87.

No power to coil: pin 30 completes the circuit to 87a.
+12v to coil: pin 30 completes the circuit to 87.

Never both. With that wiring, you would have +12v to 30 all the time, and +12v going to pin 87a anytime you're in reverse.

When you activate the coil, (86+ 85-) you would then have power going from pin 30 to pin 87, which would activate your lights.

I understand what you're trying to do, which is activate the relay automatically in reverse, with no switch, as well as activate the relay with the SPST switch. This can be done, but would have both the switch, and the reverse wiring to both be connected to the 86 pin, and you would want a diode between the reverse wiring tap, so that when you activate the switch, it's not running 12v back through the reverse wiring.

What was your reasoning to go with the SPST switch vs. an SPDT or DPDT?

 

I wanted the normal off position of my switch to be lights on with reverse. With a DT switch, it would have to be in one of the on positions to be on with reverse.

 

If you have a 2 position SPDT switch, it would either be ON with a power source, or ON, only when reverse is switched on. You would only have power going to that pin on the switch when you shift into reverse. It would be on with the switch and in ACC, and then off, until the truck goes into reverse, in which there would be power to the switch.

Kind of makes that would mean your "off" position would come on with reverse. I just chose to use the 3 position switch so I could have a "master" off, if you will.

I have a 2 position SPDT switch for my backup camera, position one, it acts just like normal and comes on/ w reverse, position 2 is on w/ acc.

 

Thanks Ryan - I guess I am making it more complicated than it needs to be. Don't know why I did not think of 2 position SPDT (on, on). For some reason, I was thinking SPDT were all (on, off, on). I think you even mention it above but you know, you only hear (or read) what you want to. That's my answer then, SPDT (on, on).