Cargo light stays on.....any ideas - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Z16 · 08-08-2011, 11:17 PM

So suddenly my cargo lite won't turn off on my 98. It goes out when the doors are open, but as soon as then interior light goes out, the cargo light comes on. So I don't think it's door switches. It works normally when the door is open and I turn on the cargo light switch. Any suggestions???

scotts62 · 08-13-2011, 10:22 AM

ttt

speedygonzales · 08-13-2011, 07:41 PM

You would have to have problems with 2 different circuits for that to occur. The interior lighting and the cargo lamp gets ground from a smart module called the interior lamp control module. It's under the center of the dash below about where the radio lines up. It has 5 wires going to it in a straight line connection. A pink wire is on one end and a white wire is on the other end of the connector.

So if this module were defective, it would lets say be putting ground on the lighting circuit. But that in it self would not light the cargo light.

The cargo light still has to be getting power from the other circuit. That of course is where the switch comes in to play. So could both circuits be defective????? I highly doubt it.

Then there's the brainstorm of some dumb ass engineer (I can say that cause I are one). That brainstorm is to not allow the cargo lamp to come on unless the interior lights is on. So this means even if the module is defective, and the supply circuit is shorted past the switch, the interior lights should still be on.

I don't think there are broken wires or wires rubbing against each other cause there are 2 circuits involved that are opposite.

This leaves me to conclude one thing. At some point in this trucks life, someone did some Rube Goldberg wiring job. Perhaps to bypass the interior lights to allow the cargo lamp to come on without the interior lights (the way I think they should work in the first place). And now that botched wiring job has gone wrong.

I could possibly lead you to points along the wiring to measure to try to find the problem.

The first thing to do is find the interior lamp control module and pull the connector off to see if the light turns off. If it does, you need to check the grey wire going to the ILCM for ground. With the doors closed, if the grey wire is grounded when you unplugged it then the grey wire is touching ground. If the grey wire has a high resistance, the module is defective. Doors must be closed to check the grey wire condition.

08-08-2011, 11:17 PM	#1
Z16 Registered User Join Date: Mar 2001 Location: Medicine Hat, Alberta, Canada Posts: 1,508	Cargo light stays on.....any ideas So suddenly my cargo lite won't turn off on my 98. It goes out when the doors are open, but as soon as then interior light goes out, the cargo light comes on. So I don't think it's door switches. It works normally when the door is open and I turn on the cargo light switch. Any suggestions??? __________________ 98 GMC Sierra Ex Cab, cowl hood, Euro LED lights, 30 bar billet, Whipple Supercharged 350 Vortec: Forged flattops, E-Tec aluminum heads, Comp Cam, Scat crank and rods, Granatelli Mass air flow, Headers, Flowmaster exhaust , Complete MSD Ignition, Custom Tuning, intake spacer , ported throttle body, AC Delco port injection upgrade, Roller Rockers, Power Pulleys. Gear Vendors Overdrive. Soon to hit a dyno. 2/4 drop(for now). 95 Chevy S-10 Ex Cab 4.3 5 Speed 2/3 drop, Euro lights, billet grill, More to come. The Daily Driver

08-13-2011, 10:22 AM	#2
scotts62 One day... Join Date: Apr 2008 Location: Tuttle, Ok Posts: 9,243	Re: Cargo light stays on.....any ideas ttt __________________ Scott 93 crew cab build Project 62

08-13-2011, 07:41 PM	#3
speedygonzales Registered User Join Date: Jan 2006 Location: Smithfield, VA Posts: 1,501	Re: Cargo light stays on.....any ideas You would have to have problems with 2 different circuits for that to occur. The interior lighting and the cargo lamp gets ground from a smart module called the interior lamp control module. It's under the center of the dash below about where the radio lines up. It has 5 wires going to it in a straight line connection. A pink wire is on one end and a white wire is on the other end of the connector. So if this module were defective, it would lets say be putting ground on the lighting circuit. But that in it self would not light the cargo light. The cargo light still has to be getting power from the other circuit. That of course is where the switch comes in to play. So could both circuits be defective????? I highly doubt it. Then there's the brainstorm of some dumb ass engineer (I can say that cause I are one). That brainstorm is to not allow the cargo lamp to come on unless the interior lights is on. So this means even if the module is defective, and the supply circuit is shorted past the switch, the interior lights should still be on. I don't think there are broken wires or wires rubbing against each other cause there are 2 circuits involved that are opposite. This leaves me to conclude one thing. At some point in this trucks life, someone did some Rube Goldberg wiring job. Perhaps to bypass the interior lights to allow the cargo lamp to come on without the interior lights (the way I think they should work in the first place). And now that botched wiring job has gone wrong. I could possibly lead you to points along the wiring to measure to try to find the problem. The first thing to do is find the interior lamp control module and pull the connector off to see if the light turns off. If it does, you need to check the grey wire going to the ILCM for ground. With the doors closed, if the grey wire is grounded when you unplugged it then the grey wire is touching ground. If the grey wire has a high resistance, the module is defective. Doors must be closed to check the grey wire condition. __________________ 99 Z71 (98 body style) Pride and joy Last edited by speedygonzales; 08-13-2011 at 07:53 PM.



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