# Roof lights



## mac3897 (Dec 23, 2002)

Is it possible to mount a small rotating beacon on the roof with a magnet mount and then wire it so that it will come on when you powered on the "Cargo Light" switch (the light that is high on the back of the cab pointing to the bed)?

It seems like it would be an easy job, but am i over looking anyting like voltages or amps or anything?


Mac


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## wyldman (Jan 18, 2001)

Yes it can be done.I would be carefull using the cargo light to run it though,some rotating lamps can suck back quite a bit of power,way more than that little cargo lamp.Then also tend to freeze up or stick sometimes,and the current draw will go sky high.I would do it with a relay.Use the cargo lamp wire to trigger the relay,and then the relay supplies fused power from the battery.Much safer to do it this way.


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## mac3897 (Dec 23, 2002)

Chris.

You woulndn't happen to have any wire diagram of this setup would you??

Mac


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## wyldman (Jan 18, 2001)

I can make one up and post it here if you wish


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## wyldman (Jan 18, 2001)

Here is a quick pic of the relay.

The accessory would be your light.

Battery power must have a fuse rated slightly higher than the max current draw of the accessory or light

The switch would be your cargo lamp switch

Ground the other side of the relay.


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## mac3897 (Dec 23, 2002)

Thank you very much.

If i put a "quick connect" plug on the rotator so i can take it off when not in use, would the cargo light still work by itself?

Mac


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## wyldman (Jan 18, 2001)

If you just tap or "T" into the cargo light circuit,then the cargo light should not be affected when the beacon is disconnected.Only thing is that you will have your cargo light on when the beacon is on,which can be kinda distracting.If you cut the wire going to it,and put quick disconnects on both then you could switch back and forth by unplugging the connector.If your going to go to all the trouble to wire it all up nice,then you may want to consider adding another switch for the beacon,and retain your cargo lamp the way it is.


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## fastjohnny (Nov 14, 2002)

*Cargo light switch*

The other problem I foresee about using the cargo light switch, is that it only functions with the door open, at least on all the gm trucks I ve owned, which has been about 7 or 8, at last count


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## WNY PAT (Dec 4, 2002)

*Cargo Lamp Switch*

I've got my strobe hooked up with quick connectors to the cargo lamp switch... been working fine all year.... although the cargo lamp does not function at all (cut the wires). It does work with the door closed.....

BTW.. I have a 2002 2500HD....


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## wxmn6 (May 23, 2001)

mac3897, I don't remember exactly what truck you have but I would guess Chevy Silverado 1500? Do your truck have snowplow prep package? If so, then there should be a switch named "Auxiliary Lamps" right next to the air bag on/off switch. If so, there is a wire between the headliner and the roof ready for you to drill a hole and permantely mount the light. I know that this is not the method that you would go with if you have this option, but you can disconnect the "accessory" wire from the switch that lead to the roof, and not use it. Run a new wire from the switch to wherever you want to leave the wire ready for you to pull up and plug the light in for use. One fair warning, I don't know if there is a relay in this circuit because if so, then you must run a wire from the relay to the light. That would mean leaving the switch alone because it would be connected to the relay. That would mean you will need to disconnect the GM roof light wire from the relay.


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## wxmn6 (May 23, 2001)

Mac, I just checked the other thread about you asking if you could put a plow on your 1500. I see that your truck have extended cab. My suggestion would be to run a wire from the switch/relay to the rear under seat and leave plenty of wire there. When it is time for you to plow, just pull out the wire that is tucked under the rear seat, and run it through the extended cab window and close it. Plug the wire to the light and you are set.


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## mac3897 (Dec 23, 2002)

Stephen

That sounds like a good idea. Forgive me for not being a master electrician  but correct me if i am wrong. What I need to do is run a wire from the cargo lamp switch (under the dash???) along the floor and under the seats then leave the wire there?

Do i have to change the size of the fuse or should i use an inline fuse? Also to I have to get a separate relay or new switch?


And yes my truck is a 1500. But unfortunatly is does not have the plow prep package. I have to figure out how to use the signature feature of this forum....nevermind i think i got it.

Thanks
Mac


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## Snoworks (Jan 22, 2002)

I tried to due this with my 1998 2500 GMC Sierra. The beacon will only come on, with the switch on, and the door open or the dome light on. There must be some type of relay under the dash; due to the following.

1) There are two hots at all times(bottom two wires), with the cargo switch on or off.
2) The top two wires(black and grey) never become hot, with the cargo switch on or off.


Very confusing to me!! How does the cargo lamp get power from the switch. One wire should become hot when the switch is turned on, and that is the one that is you lead to the cargolamp.

Keep in mind, I was going to substitute the beacon control for the cargo lamp.

Chuck B.


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## fastjohnny (Nov 14, 2002)

*98 cargo light*

This is what I was talking about in my earlier post, I think the door switch must run a negative round switch, which must be in the open position before the cargo light switch can be utilized. I played around with this one time as well, and never took the time to get to the bottom of it.

Any one else figure this out?

John


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## wxmn6 (May 23, 2001)

Sorry I forgot about this thread. It just pop back to the top. 

Now to the cargo switch stuff.... assuming that there is no relay for this circuit and that the grounding is not switched (I think this is called negative side system?). Anyway this would mean a power from the source going directly to the cargo switch on the dash. Then there will be another wire that is connected to the switch that will run up to the cargo lamps in the rear. Get a spool of 14 gauge wire and tap the wire to the wire that goes to the cargo light, and route that wire wherever you want to, such as my idea above (route and leave plenty of wires under the rear seat). If you go with my idea that I just mentioned, you will need another wire for grounding from the roof warning light to the vehicle chassis. You need to find someplace inside the truck for a good source of grounding such as bolt that holds down something. But I like to run grounding wires up to inside the engine compartment and attact it to the bolt that holds grounding straps. Get a good waterproof connectors for the light and wires. GM make several good connectors. 

To test to see if the cargo lamp on your vehicle is positive switched, take a test light and put one end of lead to the either terminal of the switch and put another lead to a bare chassis such as bolt under the dash. If the test light does not lit, then move the test lead to the other terminal on the cargo lamp switch and see if it lit. If not, then the cargo lamp is negative switched side. If that is the case, then let me know and I should be able to help you furthur.


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## Arc Burn (Oct 21, 2002)

My 99'Chevy(old body style)has a center roof console,i put a lighted switch in it and took juice off the cargo light wire which runs thru it for a highlighter light bar with zero probs.,not exactly what your askin but another option.


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## wxmn6 (May 23, 2001)

Another thing... if your switch is positive side, but the roof light won't work without the dome light on as posted by Snoworks because of relay, then you will need a separate switch for it. It is not hard to add a switch. So just be sure to leave a few feet slack of wire near the cargo light switch in case if you need to relocate the wire to the separate switch.


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## wyldman (Jan 18, 2001)

For all the trouble,you might as well keep it simple and add another switch somewhere.Use the relay as I described above,just use a separate switch to control it.Get to keep your cargo light too.


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## mac3897 (Dec 23, 2002)

Wow. The more i read this thread the more confused I get about wiring. To make this easier on myself I may just go with a cigarette lighter plug. Is there any downside to this??

Mac


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## wyldman (Jan 18, 2001)

Cig lighter plug will work fine,just you tie up the lighter plug and have wires in the cab,but it is quick and easy.


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## mac3897 (Dec 23, 2002)

Fortunatly I dont smoke and my truck actually has 3 cigarette plugs in the dash. I think this is the way to go for me.

Thanks for all of the suggestions.

Mac


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## wxmn6 (May 23, 2001)

I think cigarette lighter plug is a good idea. Run a couple of wires from the roof down through the extended cab window and leave plenty of slack tucked under the rear seat. When you need the light, pull it out under the rear seat, and run it along to the middle and plug it in. I think it should work out good.


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## JohnnyU (Nov 21, 2002)

I've seen some plugs at places like Radioshack that have switched built into them. I think this would be a good thing to find and use, you could just leave it plugged, and flip the switch when you want it on or off. Just my $.02


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## Snoworks (Jan 22, 2002)

Arc Burn - Did you have to take the roof counsel apart to expose the wires leading to the cargo lamp? Also, how did you run, hide the wire going to the highlighter? 

I have a back rack with a highlighter light bar. 

Chuck B.


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