1956 cadillac dome light question? problem...

okay so i finally got all my lights working in my 56 cadillac. problem is the overhead lights stayon all the time. i know they have constant power feed but the ground dome light switch in the door only works the map light on the dash. when you open and close the door the map lights turns on and off.... sadly my classiccarwiring.com wiring diagram has every wire on there but the dome light circuit... go figure!

any help is much appreciated of where to go next...

 

Did you check dome light to see if constant + is there?

 

well of course they have power, i just said they stay on all the time....

 

Sorry mind on to many things currently. Been on the phone alot Dad is in hospital so I totally miss read it. Thought maps worked but not dome . Gots to have a dead short on one of the white wires going to dome light then after the door switches.

 

Did you try turning the HL switch knob? Once it gets the dash lights to full brightness it should click and keep the dome light on for reading a map at night. Try turning it to the left a tad.

 

Cant be that either because that would feed back to map. Like you said need diagram. I'm refering to my last reply.

 

yeah the headlight switch has been checked as has the dome light bypass switch on the driver side lamp.... neither are it as best i can tell unless i am missing something... my thing is if the dome lights stay on because there is a bad ground why does the map light not stay on? my other thought is when i pull out the dome light switches in the door there is only one wire per switch and then they junction under the glove box and go to the map light...

so to me that is like the dome light switch only turns on the map light....

as i said of all the circuits this is the only one not on my wiring diagram...

 

thanks for the replies guys keep them coming!!!

so my question also is if the headlight switch is turned on to the right to turn on the dome lights does the map light also come on?

 

If the thought is why one wire at the the door switches heres why. There ground switches. Thats how the lamps get turned on and off. Power + is always on at the bulbs. Hope that helps, it seems you know some electrical and i'm just talk'n at this point.

 

I thot that there was a separate switch at the rear of the map light, against the dash...that would turn on the map light/off...I thot it was a separate circuit (I beleive it was on my '55 Caddy - but I rewired all of it so it doesn't work like that anymore )...and the dome light only worked with the doors and the headlight switch...

R-

 

johnny my thought was that if the dome light switch only has one wire ground and it works the map light... what works the dome light since my car seems to be workingly seperartly...

there is a seperate switch on the map light and the dome light that are made to switch them on when the doors are closed...

so i am lost now because the dome light switches work and the dome lights stay on constantly....

40 stude dude according to my wiring diagram the map light runs off of the dome light switches from the factory....

i know i could just rerun my ground wire to my dome lights and wire it to the door dome light switches but this is a 1 owner (before me) 60,000 mile original car so i see no reason to go cutting in the the wiring...

 

had the same issue with my 56 buick, found out the older vehicles would switch the b+ to turn the dome lamp on and off and use the housing of the lamp as a ground. Easiest way i found to fix the problem is wire in a relay that switches the b+ on and off when the door switches are grounded. Hopefully this makes sense. basically instead of switching ground, your switching power by use of a relay.

 

bagged 51 i am not sure what you mean really... i understand the concept of wiring in a relay but what you are saying about the other is not clicking...

on the other hand it is not from the dome light chassis grounding because i have the dome lights hanging so the only thing going to them is wiring no metal to metal touching...

 

Well then disregard what i said, didnt know it was hangin down wasnt stated, just tryin to help.

 

Then there could be a relay involved. Myself not know what the domelight socket and wires that are on the 56 Caddy is what holds me back here. If it is relay controlled then its possible the contacts have welded together. Need a Caddy person to confirm if theres a relay involved.

 

yeah sadly with no wiring diagram for the dome light i am lost... it is a red and a black wire. black of course ground red for constant.

 

See theres already a differance in GM color code for 56 for the dome lights. I know that system as orange being constant power + and white being switched ground.

 

Pull all the dome lamps. Check for ground at the black wire with doors closed. If ground there, you have a short. Nevermind the map light working, you may have a cut wire that is open to the map circuit and closed to ground on the other side. Look for this.

There will be a connector in the loom near the driver's door, this is the second most likely location, the first being where the loom enters the door. Copper work-hardens, remember, and the door wiring has been flexing for 55 years...

Cosmo

 

There was no stock "relay" on an early Cadillac ...a '54'/'55/'56 Cadillac only had about 5 or 6 fuses total for the whole car...

R-

 

So then its back to what I said in relpy 4 sentance 4. But wouldn't that feed back to map light and keep it on also. Just asking because I like learning along with person having problem.

 

I have an old wiring diagram manual made by Motors. It is a 1956 edition, so maybe I can find the dome light circuit.

It covers all the common cars, i will look for 56 Cad.

 

The way this car should be wired is that all door switches are tied together along with the actual dome light switch and of course the headlight switch. Any of these complete the lamp circuit by grounding it.

I would close all the doors and check for a ground at the actual dome light switch. You can uise a multimeter set for ohms to check for continuity, or some sort of audio continuity device. I am thinking that the dome light wiring is not connected to the door switches or the headlight switch, but is connected to the actual dome light switch, which is defective. This would then keep the dome light on all the time. The map light switch wiring sounds incorrect.

 

Just went through the wiring manual.

You said your 1956 diagram does not show the dome light. I had to go all the way back to the 1950 diagram to find out why. It is listed on all the 51-56 diagrams as "body feed". The 1950 says: "body feed dome lamp etc"

But that's the hot feed.

The grounds all tie together; door switches, map light switch, and the grounding position on the headlight switch. So, that means the map light is wired to work off the door switches and gets bypassed with the map light switch. (I had wondered if maybe it was manual switched only from factory)

So, if every door switch on your car does makes the map light go on/off, then the dome light grounding wire almost seems like it was cut off, but still having ground on the domelight side of the cut wire??

If the domelight ground wire was not cut, but just frayed and touching ground, then the map light would be on all the time.

I can see why you are asking for help, as this is a tough one.

 

thank you f and j.

D2 willys i will check for a ground but it has to be there as the dome light surrond is hanging so nothing to ground to. as for the wiring being changed or incorrect. the wiring diagram depicts it as exactly as it is wired but the body feed circuit on my wiring diagram shows everything but the dome light...

CRAP! hahaha....

 

I got an idea..


You need to find the two wire harness going from the dash to the dome light. The wires should be orange for power and white for ground. Not sure about 56 but on early/mid 60's GM, there is a pigtail with a connector hanging from the bottom of the fuse panel, then the dome harness plugs in to that, then runs along the floor,,,

So if you find that; disconnect the 2 wire connector, and jump the two orange wires back together, but not the whites. If the dome light is still on, then there is a cut-off white wire that is also still grounded on the dome side of the cut. Could be a trim screw that did it? who knows? Maybe along the floor if that's where it runs, or could be in a pillar post or in the roof edges.

 

sweet i will try some stuff over the weekend guys, sadly i have to work 12s all weekend...

 

thought of something to look at. You have a map light switch. Should have 3 terminals, with the middle terminal going to the map light socket. One of the outside terminals goes directly to ground, the other outside terminal goes to the door switches, the dome lights, and the headlight switch. Now what if the dome light wires where attached to the grounded terminal on the map light switch. The dome lights would always be on, but the map light would work with the door switches, or with it's switch.

So to put it clearly, middle to map light socket, outside to ground, all other wires to the other outside terminal of the switch.

good possibility, check it out!

 

56 diagram shows 2 terminals on the map switch. One to ground and then 2 black wires connected together in the other terminal.

 

Can u post the diagram? Would help!