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need help with wiring for car project

I've posted this to a couple of honda forums but I thought I'd try a couple of electronics forums too. Thanks for any help.

I undertook my project of adding a map light assembly into the >headliner of my 98 civic LS today. I had to remove all the upper >interior trim to pull down the head liner, but it wasn't too bad. I >mounted the map light assembly and have put everything back together. >I haven't figured out the wiring, maybe someone here can help. > >My Civic LS 4D is a '98, the dome light has two wires only. One leads >to the battery + , the other comes from the door switches. (I have the >'98 wiring diagram) The grounding comes from being screwed to the >metal frame of the roof. > >The map light is from a 2001 Civic EX 2dr. There are 4 wires (see >picture) > > >
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> >From looking at it, I'm thinking black is ground, red is (+), but >there is still blue and green. Green is possibly for the door switch >lead, but what about blue which is tied into yellow (thus tied to >white)? > >I have to make four wires become three. I'm either going to have to >tie two or leave one out. Anyone have any clearer idea of this than I >do?

As a follow-up, I decided that blue and red were both (+) so tied them together to the (+) lead. Black was ground, green was door switches. I wired it up this way and the map lights work, the original dome works, but the new dome blows the fuse when I turn it on. The new dome is what's related to the blue wire (if you look at the picture it should be clear) So evidently I can't just tie it to the red, although if I exclude it there is no (+) lead to the new dome light. Can anyone figure out how I might wire this differently? Thanks.

Reply to
Kevin Van Sant
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Only a Honda wiring diagram will tell you.

Reply to
mc

I suspect the blue wire needs to tie to the other yellow wire in the picture, or to switched ground at the end of the blue wire not shown in the picture.

Here's why: Some cars (all cars?) are wired so the the door switches are grounded when the door is open. I suspect yours is wired that way. What that means, if it is true, is that when you are in the car with the doors closed and you use the dome light switch, the switch grounds the light.

From the look of the switch, I'm guessing that the switch connects the black (presumably ground) wire to the yellow wire (that is tied to the blue wire) when you turn the dome light on.

It looks like the red wire (+) goes to the spot lite on the left of the picture and connects to the white wire at the spot. The white wire goes across to the spot lite on the right side, where it is joined to a yellow wire that goes to the dome light. Therefore, the dome light is connected to (+). That means that the other yellow wire to the dome light *must* get connected to ground by the switch to turn the light on. That yellow is the one that is currently tied to the blue. If you tied blue to (+) and then turn on the switch, it has to blow the fuse.

That leaves the question of where did you connect the blue wire to (+) ?

Ed

Reply to
ehsjr

Thanks, I think I finally have a clear picture of what's going on. I did in fact get it working a short while ago simply by dead-ending the blue wire. I appreciate your detailed response.

I had earlier tied it to the red wire (+) to the same (+) lead which fed the existing dome light. Your description explains why that failed.

Reply to
Kevin Van Sant

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