Hi, I am having a problem with wiring in my dome light into my 48 Ford, I have a dome light with the centre bulb and the 2 reading lamps on each side with a switch to turn them off and on, with 2 wires coming from it. I have the easywire fuse box and the push buttons for the doors, But I'm am just not to sure how to wire this in, if anyone can help with a drawing that would be great, thanks.

 

Hum, Julie will be along shortly (?) but here is a cyberspace guess. For the map lights to work without having to have the door open you would need two power wires, one fused but always hot for the map lights and one switched by the door switches to turn on the interior / dome light when you open the door. Both circuits are going to require a ground so is there a ground via one of the mounting screws and is it into the metal body, not plastic?

OH, here comes the diminutive one!

 

The door buttons have grounds coming off of them which is grounded to the body. The dome light I assume is grounded by the mounting screws which do go into the metal.

 

Why, the door switches are just that, a switch off / on, no reason to ground them other then to let the factory smoke out of the wire?

Assumptions and wiring are not a good combination, causes the above to happen!

JULIE HELP!

 

Ok Try one of these depending on your set up, switch types and local control (switch on the light?).

For mine I mounted a second very dim light for the door switches and left the overhead (above the back window) on a seperate switch. I did it that way so at night th elight high in the cab wouldn't blind you - the small one under the dash for the door switches provides just enough light to let you see what you are doing in the lower half of the cab.

There are lots of variables, but pick one of these based on what configuration you want. "HOT BUS" is hot power on all the time, "SWITCHED BUS" is power turned on with your ignition switch.

 

There are two types of door switches: One has one tab on the back and one has two tabs on the back. These function EXACTLY the same as the two types of starter buttons we have talked about tons of times.

If your switches have a single tab, they provide a ground through the body of the switch for the circuit when the switch botton extends. So, you have to run power to the light first, then a wire down to each switch to provide a ground (and thus light on) when the door opens.

If your door switches have two tabs on the back, then power runs into the switch (which is not grounded by the switch case contacting the door jam) then out to the light which is grounded.

You can not have both the switches and the light providing a ground - only one or the other. And which ever one doesn't provide the ground, gets the power applied to it.

 

This often uses a unique anomaly, a single filament bulb with two contacts (one for the ground) with an isolated, non-ground base. Usually for a stock and not an aftermarket lamp.

 

Yes my door contacts do have the two male contacts, one of which is comes out and is grounded to the body.

 

So you have one of the posts on the switch that has a wire running to ground?!? That's probably the problem. That should have power flowing into one tab then when the button pops open (and closes the switch) power should also flow out the other tab and then up to the light - which is grounded.

Best way to be sure is take a meter and check to see if (when the button is allowed to pop up) if the switch provides continuety between the two contacts, or if the switch provides continuety between either (or both ) of the contacts and the switch casing.

Then check to see if your light casing has continuety to ground (via the case itself or tabs on the back or the switch) - probably does, and the door switches probably provide continuety between the posts. If that's the case, then any of the drawings above will work - depending on what configuration you want. The 56 drawing is OEM.

If your light case is not grounded and you HAVE TO use the door switches as grounds, then you can wire it like this:

.

 

OK I will do that, thanks for the info everyone.

 

I know this thread is old but.

What if I wanted to have a switch at 4 doors, Im building a 56 f100 crew cab and am going to have two stock dome lights, and 4 stock style door switches.

I would like both lights to come on when any of the doors are opened, as well as from the headlight switch.

I would also like to be able to turn both the dome lights on from either switch on the actual dome lights.

can it be done?

under dash curtisity lights might be nice too.

 

 

That is fine if using modern self grounding switches.

Im using stock switches. The dome light is the ground.

 

You have 2 choices. You can change your switches to the grounded type and follow the above diagram, which would make life very simple. Or you can reverse the power flow as shown and run hot wires to all of your switches that will send juice to the lamp, which would be grounded. That's a lot of extra wire and a lot more areas for problems, which is why the OEM went the other way.

 

Then connect the second wire from the switch to ground. One thing not discussed here (or at least I haven't seen it) is the difference in how the dome light is grounded. Sounds like OEM dome lights are one wire with the ground thru the light base. If that is right then it won't work with modern one wire door switches. But this tread was started with the idea of using a modern dome light with integrated reading lights.