Switched power

[hrdas]

Hello everyone. I'm a new member 5 min old from canada lol, I read a thread in here from 2021 about hooking up 12 volt accessories, these were all low amp dash cams eg. I am hooking up a rear defroster for my cap, that's on my 5 gen 1500 LTD 5.7 Hemi. This requires a 20 amp switched power source. I don't want to randomly pick the pink and yellow as I Do not want to creat faults with the computer.
Any thoughts on where in the internal fuse panel I can tap this from? Thank you

 

[crash68]

if it's for a cap over the bed, you may want to tap a circuit from fuse panel under the hood. It already outside the cab to run back to bed of the truck.
i have to ask if this defroster is for a bed cap, what's the point? The view out a cap is so limited in what you able to see even on a good day, relying on it for driving can make for dangerous situations.

 

[hrdas]

I keep it clear for the dash cam and to keep an eye on those not paying attention behind me on the highway. Your point is a valid one, none the less every bit of helps.
As the relay is mounted next to the steering column I want to keep my feed as short as possible to maximize the current in the cable.

 

[Brandon-w]

Yeah I'd definately take power direct from The battery with a relay and wire your trigger to ignition and have it switched that way it will always shut off with key off. It's also far easier to run one wire out to the relay and less risk on the factory components you'd be robbing power from in the fuse boxes.

 

[hrdas]

The switch is hard wired into the thermasync control module / relay
They give you one option that is a fuse tap.
They say you can go direct to the battery but highly recommend you use a switchable wire that can handle its own amperage plus the 20 for the defroster. I get running from the battery after that would run it to a external relay..... Then where does the link happen to a switchable lead?

 

[GTyankee]

I seem to recall that under the bed, there is a wire Loom, for lack of a better name, that wire(s) is just tied off.
It was left there, so that if a light is needed in a topper or camper.
I would think that it runs along the cross frame in front of the spare tire.
Directly above the rear axle ?

 

[Badger 13]

Welcome to the forum. A defroster would draw more amps then any lights for the cap. I have to agree with what Brandon-W said. I think that would be the best and safest way, plus it would not mess with the canbus, or other internal system.

 

[hrdas]

Thank you for all for your suggestion and ideas. I'm trying to wrap my head around your concept of hooking up to the battery,
I get that now that goes to the power side of the relay. Here is where I get lost, as I need to hook into a switched power source., would this not in sense create two power sources that feed my thermasync? Then the lead from the switch power would have to become the dominant power source? I was thinking of taping into the sunroof power lead of 30 amps as I wouldn't be using it at the same time anyway lol. I still prefer your idea of the battery.the attachment is what I'm following I have everything hooked up except the power at this time.
Thanks for your patience and help.

 

[G-Ride990]

Isn't there a 20 or 30 amp switched lead in the 7 pin trailer hitch plug at the rear of the truck already? Could you tap into that?

If you hook W5 directly to the battery or constant 12v source then the relay would have power at all times.

W6 is the trigger wire to actually turn on the heater.

So if you went directly to the battery that would mean that you could turn on the heater with the truck on or off.

That's the only difference I see.

Edit: Added some info

 

[18CrewDually]

Isn't there a 20 or 30 amp switched lead in the 7 pin trailer hitch plug at the rear of the truck already? Could you tap into that?

That's a good idea but it is hot all the time. He may be able to switch it to a key on hot though.

 

[G-Ride990]

That's a good idea but it is hot all the time. He may be able to switch it to a key on hot though.

One of the 20amp circuits is switched with running lights on I think. Wonder if that may be the way to go.

Hot all the time wouldn't bother me but if that controller/relay fails, might cause a parasitic draw on the system.

 

[hrdas]

What if I tap into F25 as I don't trailer in the winter anyways

 

[G-Ride990]

What if I tap into F25 as I don't trailer in the winter anyways

There are plenty of options depending on how you want to run it.

I would like to add, there is a Curt T harness that is made to tap into the trailer wiring for various applications. Before you go T-tapping OEM wires, I would suggest you take a look at that.

I think most guys around here use that T harness to connect a tailgate light bar. I think you could use the same harness for your needs.

 

[hrdas]

Thanks I will look into that as well, it was suggested earlier so I will need to see where it comes in near the cab? Guess that will be next weekends project lol

 

[ANGLICO]

I seem to recall that under the bed, there is a wire Loom, for lack of a better name, that wire(s) is just tied off.
It was left there, so that if a light is needed in a topper or camper.
I would think that it runs along the cross frame in front of the spare tire.
Directly above the rear axle ?

View attachment 532029

Would that termination in the harness also have one for the bed lights? My Power Wagon supprisingly did not come with the bed lights installed (but it has just about everything else). I guess I should search for a Bed Light wiring thread.

As always, thanks for any advice/G-2 on how to!

 

[GTyankee]

Anglico, is your Ram a Classic or New Body Style

if it is a Classic, you should read this

Bed Light Pre-wired?

Hey y'all, I have a 2019 1500 classic and am wanting to put in some bed lights. Is my truck pre-wired for this or do I have to wire it myself? Thanks Bob

www.ramforum.com

 

[ANGLICO]

Anglico, is your Ram a Classic or New Body Style

if it is a Classic, you should read this

Bed Light Pre-wired?

Hey y'all, I have a 2019 1500 classic and am wanting to put in some bed lights. Is my truck pre-wired for this or do I have to wire it myself? Thanks Bob

www.ramforum.com

Thank you.

I also watched a YouTube where the owner had to have the PCM reprogrammed by the dealer to recognize the lights, after installing an OEM bed light kit and harness.

I'm not there yet.

Much appreciated. Like the tryke. I'm a bagger guy.