Does the dome light have to be on for the cargo light to work - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Accelo · 11-18-2021, 01:48 AM

Does the dome light have to be on for the cargo light to work?

I have converted my cargo light to work both as a third brake light and a cargo light using one of the LED conversion lamps. I managed to get the third brake light wiring through to the cab light area without difficulty. Getting the factory cargo light harness is another thing. I have plugs or prongs on the wire no matter which way I pull it. I am not having any luck feeding it through even though I have a pull wire fed through. My 70 is a California truck and also has a tank vent line for the Charcoal canister in this same space. That have obviously added to the difficulty. I took a picture looking up into the area between the back window and driver’s door.
The other picture is the wiring I am attempting to pull through. Last is the unreadable wiring diagram.

I want to know the dome light has to be on for the cargo light to work in the factory configuration? It kind of looks like it. However, the wring diagram, in the assembly manual, isn't very clear. If that's the method it functions, I could just make the connections at the cab light using the existing wiring for the dome lamp and not even need the second wire to the fuse panel.

mr.mud1 · 11-18-2021, 06:50 AM

yes sir,on my truck,if you turn the cargo light on,open the door to light the dome light,the cargo light comes on or if you're in the truck,turn the headlight switch knob to turn on the dome lamp,the cargo light will light,if it's switched on.take care.Greg

**special-K** · 11-18-2021, 07:12 AM

Yep, only comes on with the dome light. The switch is to turn the cargo lamp on or off with the dome lamp

Accelo · 11-18-2021, 02:28 PM

Thanks for the responses.
I am a little surprised GM added a complete and separate harness for the cab light as the dome has to be on anyway. I am sure they did a cost analysis as GM doesn't spend a dime unless they had to. Besides, it would be way easier to accidentally leave the cargo lamp on if it wasn't tied to the interior lamp.
I am going to splice the harness. The total load on the wire may still be down as the interior lamp and the cargo light are both LED's. I all ready have a separate wire ran for the third brake light.

11-18-2021, 01:48 AM	#1
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,164	Does the dome light have to be on for the cargo light to work Does the dome light have to be on for the cargo light to work? I have converted my cargo light to work both as a third brake light and a cargo light using one of the LED conversion lamps. I managed to get the third brake light wiring through to the cab light area without difficulty. Getting the factory cargo light harness is another thing. I have plugs or prongs on the wire no matter which way I pull it. I am not having any luck feeding it through even though I have a pull wire fed through. My 70 is a California truck and also has a tank vent line for the Charcoal canister in this same space. That have obviously added to the difficulty. I took a picture looking up into the area between the back window and driver’s door. The other picture is the wiring I am attempting to pull through. Last is the unreadable wiring diagram. I want to know the dome light has to be on for the cargo light to work in the factory configuration? It kind of looks like it. However, the wring diagram, in the assembly manual, isn't very clear. If that's the method it functions, I could just make the connections at the cab light using the existing wiring for the dome lamp and not even need the second wire to the fuse panel. Attached Images

11-18-2021, 06:50 AM	#2
mr.mud1 Registered User Join Date: Dec 2020 Location: Joggins Nova Scotia Posts: 1,599	Re: Does the dome light have to be on for the cargo light to work yes sir,on my truck,if you turn the cargo light on,open the door to light the dome light,the cargo light comes on or if you're in the truck,turn the headlight switch knob to turn on the dome lamp,the cargo light will light,if it's switched on.take care.Greg

11-18-2021, 07:12 AM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: Does the dome light have to be on for the cargo light to work Yep, only comes on with the dome light. The switch is to turn the cargo lamp on or off with the dome lamp __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

11-18-2021, 02:28 PM	#4
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,164	Re: Does the dome light have to be on for the cargo light to work Thanks for the responses. I am a little surprised GM added a complete and separate harness for the cab light as the dome has to be on anyway. I am sure they did a cost analysis as GM doesn't spend a dime unless they had to. Besides, it would be way easier to accidentally leave the cargo lamp on if it wasn't tied to the interior lamp. I am going to splice the harness. The total load on the wire may still be down as the interior lamp and the cargo light are both LED's. I all ready have a separate wire ran for the third brake light.



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