There should be 12 volts on the orange wire at the bulbs. The switch controls the ground side of the circuit. There should be 12 volts on the blue w/white wire at the switch. The switch will ground that wire and complete the circuit and the cargo lights will turn on.
to check the switch you would unplug it and check for continuity between the pins that the blue w/wire wire and black wire go to.
I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa
Ok continuity is good between. Blue w/white and black. Do u know of a way to bypass the switch to see if it's in the wire.
What about the other things i mentioned. Do you have power on the orange wire. Is there power on the Blue w/ white wire?
Jump the blue w/ white wire to ground or to the black wire at the connector.
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SOURCE: under dash wiring harness for electric brake
1998 there are no hook ups are t.s has to be hard wired, The questions is where is the blue electric brake wire under dash and the cold brake wire
?? Anyone knbow ??
SOURCE: 2004 chev silverado Z71 1500 4wd
That was a good suggestion by Molson. Also, if you have been doing a lot of heavy hauling, have them check the strainer, which could be a problem as well.
SOURCE: 1999 Chevy Silverado - 3rd Brake Light Inop
if you can trace the wires and look for a loose jack or broken wire
Testimonial: "Thank you. I'm sure it's narrowed down to a wiring issue, but I am not sure how it is wired."
SOURCE: cargo brake light works but my rear brake lights
check wiring harness behind light assembly for a loose or broken ground wire. this would not affect the third or "cargo" brake light
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just checked the wire harness. there are three wires for the switch . black blue and brown. ive narrowed the brown to be hot. i touched the blue and black togather and the cargo indicator light on the dash turns on but the cargo light doesnt work.. i check the brown and the blue and i get around 12 v. how do i check the switch
Ok . Continuity is good on the the switch for the blue w/white and black. Still no light. Do u know of a way to bypass the switch to see if it's between the switch and the fixture. What I'm scared of is that the fog light part (lower)is good but the cargo light (upper) isn't.
No power to the orange at the fixture. Blue has power. I will try to bypass the switch after work today
That's impossible. The light is ground side controlled. This means there is power to the bulb all the time. The switch completes the ground side. If there is power at the Blue w/ White wire than there has to be power on the orange wire. There cannot be power on the Blue w/ white wire if there is not power on the orange wire. If there was there would be a short and as soon as you turned the switch on the fuse that protected the circuit that was shorted to the blue w/ white wire would blow.
I just checked the orange wire on the fixture on my lunch break. Orange is dead and blue is live. In the harness in the back of the switches that control cargo and fog green and blue are live. I go to the fixture and all are dead except blue for the third light. Is there a fuse for just the orange wire to the cargo.
What are you checking these wires with? A volt meter or a test light?
Volt meter
Good. You have the negative lead on a good ground and your using the positive lead to check the wires? Are you checking the wires at the connector? Are the connectors plugged in or unplugged.
Sorry for all the questions but something doesn't make any sense....
I'm checking the wires at the connector and grounding to the metal frame o the fusebox at the switch and at the fixture I'm grounding to the screw hole to the fixture. Im getting a reading on the 3rd light so I assume I'm getting a good ground.
Connectors are unplugged
Ask me all the questions you want. I just appreciate the help and quick response. I'm just clueless right now.
I bought the truck a year ago and the lights have never worked. Maybe they are in the harness wrong. Do u know what order they are supposed to be in or does that matter right now.
Let me check a couple of things at work tonight and hopefully I'll have some more info for you. It will be later tonight before I get back to you.
Thank you I appreciate it.
Here's what I think is going on. The voltage you are seeing on the blue with white wire m ay be from the BCM. it's not real clear but the BCM monitors the cargo lights and shuts them off after 10 minutes. If it sends voltage on the blue with white wire it would know when the switch was on.
That still leaves us with no power on the orange wire. I believe it gets power from the courtesy light fuse in the underhood fuse block so it may be worth your time to check those fuses. That power then goes to the under dash fuse block where it is distributed to two other lights. And to the cargo lights.
You said it comes on in reverse? The only time they should come on is when the switch is on so it may be possible that the previous owner modified the wiring to have the cargo lights come on when the transmission in reverse?
You next step would be to find the connector 3 bulkhead under the dash and look for pin M. It should have an orange wire. That is the feed to the cargo lights. If there is power there then you know that the problem is in the harness between the bulkhead and the cargo light. If there is no power and the fuse has power than you know the problem is I between the two fuse blocks.
i got a 12v reading off m under the dash. after following your instructions i had no choice but to pull the headliner down (was trying to avoid that). i found a 3 inch section missing from the orange wire. my assumption would be the previous owner left the light on until the wire burnt up. thank you for all your help.
I Agee, I hate pulling headliners but you have to start somewhere. Sounds like it should be back to working after the repair is made.
Yes. I repaired the wire and all works well. I learned a lot thank you for your help!
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