Need help with Carling Switch for Cargo Light

[dr09fronty]

Need a little help with a switch. I purchased a couple of Carling switches from OTRATTW like these:

OTRATTW

I plan to use one for when I install my new PIAA 510s and the other one will replace the factory cargo lamp switch.

Right now I’m working on swapping out the cargo switch but I can’t get the top light of the rocker switch and the cargo light to come on at the same time. I either have one or the other. When I use the factory wire configuration I get 8.23 volts to the source terminal (2) and I can turn the cargo light on/off but the top rocker switch light does not come on. If I run 12 volts to the source terminal (2) the top switch light will illuminate but not the cargo light. I’m obviously missing something.

I’ve attached a document from another post showing the pin layout. I’ve researched this forum looking for similar problems but couldn’t find one that was specific to the cargo lamp.

Any help is greatly appreciated and I hope that I don’t lose my man card over this.

[Jakea333]

Just taking a look at the wiring diagrams, it looks like the factory switch just closes a grounding wire from the BCM. So, when you're using the factory wires your top light is a resistive circuit in parallel with a short circuit (I'd think it's possible your top light is just getting so little power it's not producing any significant light).

Assuming the output from the BCM doesn't produce too much power for the light in the switch, I'd try to wire the output from the BCM (the input to the stock switch) into terminal 2 and then only ground terminal 8 (which could be the wire out of the stock switch, but shouldn't have to be). This extra resistor could cause the BCM to not see exactly what it wants (I don't know what it's looking for on the output), but I'd guess that it will work.

That's my elementary circuits 2 cents.

[dr09fronty]

Thank you. Let me digest this information and study up on the BCM. While I'm at it I need to find a more detailed wiring diagram. Thanks again.

[Deep Water Dan]

Jakea333 is on the right track. All the cargo lamp switch does is complete a signal to ground for the BCM. I'm making some assumptions here; one is that you grounded pin 8, two is that you did nothing with pin 3, and the third is that the switch internally applies the input from pin 2 to both the other side of the indicator light in the switch and to pin 3. So if that's the case, when you have the factory wire connected to pin 2 and you close the switch it completes the ground through the indicator light in the switch. The cargo light comes on but the light in the switch doesn't because it presents a low enough resistance that there's no voltage drop to speak of across it. When you hook up 12 volts to pin 2, all you're doing is powering up the light in the switch. The cargo light won't come on because you haven't provided a ground to the BCM via the factory wire. The reason I assume you did nothing with pin 3 is that you'd probably be blowing some fuses or the BCM when you connected 12 volts to pin 2. It looks like what you need to do if you want to have a lighted switch in the cab for the cargo light is to run 12 volts to pin 2, ground pin 8, and run a wire from pin 3 to the terminal on the cargo light relay that feeds the cargo lamp. That would retain the ability for the cargo lamp to come on when the doors are opened.

If I'm wrong about how you have it wired tell me exactly you did with pins 8 and 3 and what you are doing with the factory wire when you have 12 volts connected to pin 2 and I'll look at the wiring diagrams again.

Dan

[inov8]

Try this:



The 1N4001 diode is required to prevent +12V from backfeeding into the BCM.
Be sure you have the version of the switch with an incandescent lamp between terminals 3 and 8. The LED version will not work. Either LED or incandescent lamp is OK between termials 6 and 7.

The upper lamp will turn on when the switch is closed AND the accessory bus is hot (ignition key in ACC or ON position).

[dr09fronty]

Thanks Dan! I probably will not be able to get back to it until this coming weekend. I'll let you know how it goes once I have a chance to make the connections.

Appreciate your time and help.

David R.

[dr09fronty]

Thanks inov8, love the diagram! I'm a visual kinda guy so that helps.

David R.

[dr09fronty]

I’ve attached an image of the original wiring (as I was taking it apart) and the original switch from Nissan. Here is how I connect the wiring to the Carling switch: gray wire to terminal 2 (power source - 8.23v constant), pink to terminal 3 (for the cargo light), black to terminal 7 (lower light negative) and purple to terminal 6 (lower light positive). For the ground, terminal 8, I ran it to the power outlet negative.

The purple wire is providing 12v switchable. The lower light works great, comes on when dash lights come on, working as expected. So I'm okay with the wiring on terminals 6 and 7.

I tried a quick test tonight running 12v constant to terminal 2, pink on terminal 3 and grounded 8. I pulled the 12v from the power outlet by the center console next to the glove box. I checked the current on the power outlet with a multimeter so I know the voltage and ground from the power outlet are good. So with 12v going to terminal 2 I flipped the switch; the top light of the switch came on but the cargo light did not and I could also hear a slight buzzing sound by the relay. At that point I turned the switch off and called it quits for the night. Everything still works ok, engine starts, etc...
next step is to try Deep Water Dan's suggestion to run a wire from term 3 to a terminal on the cargo light relay that feeds the cargo lamp.

[Jakea333]

I had a few more minutes to look at the wiring diagram, so let's see if we can finish ironing this one out.

First, a few things about what we've got. I didn't realize the stock connector had 4 wires, now it makes a bit more sense (for reference, your truck has wiring colors associated with the 2010 FSM I had, not the 2009, but the pin-outs are the same). Those 4 wires are:
Pin 1 = Gray - Signal from BCM to switch
Pin 2 = Pink - Ground wire for the stock LED illuminating the switch
Pin 3 = Black - Ground wire for switch
Pin 4 = Purple(Violet) - Power wire from tail-lamp circuit that controls most dash illumination (comes on when your tail-lights are on)

This means the purple and pink wires are only used to power the LED that back-lights the stock switch. So, assuming you want the lower light to illuminate with the rest of your dash lights, they are perfect to match up to pins 6 and 7 on the new switch. It shouldn't matter which to which, but following convention on the switch diagram that would be purple wire to pin 6 and pink wire to pin 7.

Now, the cargo lamp switch in stock form only uses the gray and black wires. Moral of the story, when the switch closes they are connected allowing the signal on the gray wire to be grounded. When the gray wire is grounded the BCM thinks the switch is on and enables the cargo lamp.

The best way to give the new switch stock functionality will be to use the diagram inov8 posted (nice work, by the way). To do this, take the 12V constant that you have been using and attach it to pin 8 on the new switch. The gray wire will go to pin 3 on the new switch, but a diode must first be installed in-line to prevent current feeding back into the BCM. Something like this should suffice and will probably be in stock at your local RadioShack. You'll need to make sure the diode is facing the correct way or it'll have the opposite effect.

Finally, the black wire from the stock switch is a body ground, and should be perfect for the ground on pin 2 of the new switch. If that's all installed correctly, it should work just like the stock switch (while looking much better of course).

To note, simply running a wire to the stock relay will not work in the way Dan mentioned. The relay has a 12V power source from the battery already, it needs a ground to complete it's circuit (which the BCM provides when it needs to switch the lamp on). You could use the switch to create this ground in a similar way to what's above. This would involve splicing into the pink wire from the relay (without severing it) and running that wire into pin 2 of the new switch. Then I'd use the black wire from the stock switch to ground pin 8 on the new switch, leaving pin 3 open. This wire should have enough power to adequately power the light on the switch.

The second configuration should have a similar result, and maintain a mostly stock functionality (still comes on with open door, etc.). The only thing I don't think this will allow you to do is manually turn the light off when it's on from an open door (in stock form if the switch is turned on then off the lamp turns off no matter what state it is in).

That's what I'd do anyway. Hope this helps!

[Deep Water Dan]

Originally Posted by Jakea333

To note, simply running a wire to the stock relay will not work in the way Dan mentioned. The relay has a 12V power source from the battery already, it needs a ground to complete it's circuit (which the BCM provides when it needs to switch the lamp on).

Sure it will. I told him to run the wire to the cargo lamp side of the relay where it will power the cargo light directly with the 12 volts from the switch. He won't be activating the cargo light relay, just bypassing it. But the relay will still be functional when a door is opened.