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Replace Interior Incandescent Lights with LED's and Re-Wire Galley Light [message #356194]

Sun, 28 June 2020 13:37

Clark76

Messages: 62
Registered: February 2010

Karma: -2

Member

I replaced the interior incandescent bulbs with LED light bulbs on the interior of my GMC. This is a long-overdue project to reduce the interior Amperage load on each circuit and extend battery life.

What I found, is there is only one fixture (Pair of Galley Lights above sink) in the RV that has the polarity reversed. For some reason, the barrel of the fixture is (+Pos) and the Pin (-Neg). As a consequence, the new LED lights will not work.

I have to reverse the polarity where the pin is now(+Pos) and the Barrel (Case) is now (-Neg) to get the LED lights to work.

What also makes this complicated is the fact that the switch above the Galley is wired on two separate circuits through one Double pole/Double throw switch. I am not sure if this was original to the manufacture or something the previous owner did.

Now all white lines are Grounds (-Neg) going to the bulb body, and the black line going to the bulb pin end is now (+Pos) to be consistent with all other fixtures in the interior.

To accomplish this I eliminated the connection of the power side +Pos from Fuse Circuit #1. Now both Galley Bulbs are powered by Fuse Circuit #3. This can now be done due to the fact that the new LED's are so much lower in current draw that Fuse Circuit #3 is now not overloaded with the additional bulb. This does however require the switch by the Door to be on to operate one or both lights above the sink. This also eliminated two different Circuits going through the same double pole / double throw switch.

See attached link to:
http://www.gmcmhphotos.com/photos/g7304-12v-dc-house-wiring-update.html
1) A wiring diagram I have drafted on GMC Photos. This includes, reversing the polarity on the Galley Switch to have it consistent with all other lights.
2) Summary of Main Coach interior 12V Fuse Circuit Box (Glass Fuses) located next to old "Buzz Box" and the pre/post amperage loads across circuits after re-wire of Galley Light and installation of LED lights in the interior.

If you see an error in my ways, I appreciate the feedback.
(Novice Electrician - know just enough to be dangerous) Shocked

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Re: Replace Interior Incandescent Lights with LED's and Re-Wire Galley Light [message #356212 is a reply to message #356194]

Mon, 29 June 2020 06:10

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Was there a reason you could not just reverse the connections of the shell and pin wires coming from the lamp? I've replaced the OEM lamp so I can't exam its wiring.

My new lamp has a simple ON/OFF switch with both lamps wired in parallel. So I wired the power as normal but through a 5 Amp diode. I wired the power from the switch by the door through another diode, but to the lamp side of the switch. This lets me turn ON the lamp from the door or the light itself. Both switches must be OFF for the light to turn OFF.

The diodes just isolate the power feeds from two different fuses.

JWID

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: Replace Interior Incandescent Lights with LED's and Re-Wire Galley Light [message #356215 is a reply to message #356212]

Mon, 29 June 2020 09:06

Clark76

Messages: 62
Registered: February 2010

Karma: -2

Member

I thought about doing just what you suggest just reversing the pin ends and the shell ends; however, since originally each bulb has a different (+Pos) lead from 2 different circuits Fuse #1 and Fuse #3, this would mean that the switch would have to be re-wired to allow each pole of the switch (DPDT) to handle each of the separate fused positive currents. I was not comfortable having two (+Pos) loads through the same switch due to the age of the switch.

Originally, the pin ends are (-Neg) and go through the switch which was less problematic with a common ground and probably why it was originally wired that way. But as previously noted, it will not illuminate LED lights with the pin end (-Neg).

So... Erring on the side of caution, I elected just to eliminate the circuit Fuse #1 for this one Galley light only. The remaining Fuse #1 power still goes to the 2 couch lights and the Roof Vent Fan. Originally,Fuse #3 side powered the 2nd Galley Light (Two lights side-by-side with Off/On/On slider between). Note: Galley Light Switch at the door must also be on.

Now, With Fuse #1 side eliminated, and (+Pos) on the pin's and (-Neg) on the Shell(or Barrel) Both Galley lamps are powered by Fuse circuit #3 which can easily handle the additional bulb since all bulbs are now LED's and amperage draw is much lower.

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Re: Replace Interior Incandescent Lights with LED's and Re-Wire Galley Light [message #356217 is a reply to message #356194]

Mon, 29 June 2020 09:34

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Clark,

Your mis-understanding the switch is very understandable....

That switch is not DPDT in the normal consensus. It is a three position two pole switch and it is set up to allow one to select between one or both bulbs. On boats (and one GMC). Mine was set up so you can bring up one bulb that is red for doing things night driving or just one bulb for normal owners.

I really does not matter what you do as long as you document it in the coach's paper work.

And yes, I have run into reverse polarity on many of the coach's lighting fixtures - Inside and out - My DOT lights were all backward. After the first failure, I wired all the rest with the system hot.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: Replace Interior Incandescent Lights with LED's and Re-Wire Galley Light [message #356218 is a reply to message #356217]

Mon, 29 June 2020 09:57

Clark76

Messages: 62
Registered: February 2010

Karma: -2

Member

I could not agree more. I continue to make "upgrades" to my coach. I have not yet documented all my upgrades but need to do so.

That is why I am starting to update not only for my own "GMC Coach Manual", but also take advantage of the GMC Photo's Archive and create albums on that site to contain my feeble documentation as a more permanent archive for me as well as to enlighten others. With the added benefit of this Forum and GMC Photo's archive for welcomed feedback.

http://www.gmcmhphotos.com/photos/g7304-12v-dc-house-wiring-update.html

Thanks

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