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View Full Version : 51 Commander Interior and Map light set up



lelshaddai
03-09-2018, 02:45 PM
I have almost all the electrical figured out on the 51. The Interior lights and map light are still confusing. Someone gave the proper loop of the wiring but I have too many issues and questions. I have looked at the wiring diagram for several hours and figured some things out.

Here is what I think I know.
The new wire along the driver side roof is power and goes to the map light and dome light.
The new wire on the Passenger side roof is the ground. It connects to the headlight switch and when you turn it left it provides ground. So this ground wire from the headlight switch splices into the map light ground, door switches and pillar switch.

The idea is when you turn the lightswitch to map it grounds the map and dome light. If the switch is off the door switches when open provide the ground. How is the pillar switch fit in this? It had a wire going down to it.


The problem I have are the dome and map light ground themselves when the housings are screwed in. This car had a headliner fire previous to when I bought it. How is the housing shielded to not provide ground? How goes the map light housing not provide ground. I thought of using rubber pads between the housing and frame and using plastic screws to hold it together.

jackb
03-09-2018, 03:36 PM
study the wiring diagram some more.....ground wires are well defined.... very primitive for your vintage car.....be sure to have a clear copy when diagnosing...GL

StudeRich
03-09-2018, 05:15 PM
I think you have misunderstood a few things about that circuit.
Correct me if I am wrong, but I just find it very hard to believe that the GROUND wire would go to a "Hot" switch like the Headlight/Inst./Dome Switch.

The way I understand it, the tricks are ALL in the Dome Light Assy. :ohmy:

The reason it has a Dual Contact Bulb with only ONE Filament is the POWER goes to the switch and bulb but the GROUND goes to the Second Contact so that the Switch controls the Power to control the MANUAL function and the GROUND to the other Bulb Contact is operated by the grounding door switch.
So the Bulb Bayonet Base does NOT ground like most Bulbs! :ohmy:

Does that help at all to understand it?
The only part I am not 100% sure of since I only work mostly on '54 and up without a Map Light and a Rear Seat Dome Lt. is how that differs from the Newer models I know as described above. :confused:

lelshaddai
03-09-2018, 09:01 PM
OK, here is how this works. The headlight switch can turn left or right. The turn to the right has power to it and it turns on the dash light. The dash lights are grounded to the body. If you turn the switch to the left it grounds. That is why the map and dome light have constant power to them. The door switches, light switch, pillar switch are all tied together. They are contacted to the body and ground when activated. So I have that fixed.

The problem is how the map and dome light mount. The way they mount is screwed into the body which causes it to ground and stay lit. There had to be something that insulated them from the body. Looking for information.

TWChamp
03-09-2018, 10:11 PM
Have you looked inside the rear dome light socket to see if it has 2 contacts and should use a 2 contact bulb?

I haven't looked at my 1950 in years, but will check my shop manual later tonight.

lelshaddai
03-09-2018, 10:35 PM
Yes, I have a two contact bulb in both map light and dome light. They work perfectly when not screwed to the body. All the switches work as they are supposed to. That is when they ground out. I could not find anything in the manuals.

TWChamp
03-09-2018, 10:49 PM
What is the number on the bulbs?

BRUCESTUDE
03-09-2018, 10:50 PM
Just remember that 6V is positive ground, and the switches complete a path to ground instead of a path to "hot"; sort of backwards from 12v systems with negative ground.

lelshaddai
03-09-2018, 11:12 PM
Previous owner put in a 12v negative ground harness and did not connect anything interior. I am having to pick up the pieces.

TWChamp
03-09-2018, 11:45 PM
The map and dome bulbs should be number 88 and they pick up the ground by the headlamp switch, door switches, or door post light switch.

If someone installed a dual filament bulb in place of the single filament #88 bulb, then that could be screwing things up.

The housing for the light bulb doesn't matter if it's grounded, as it's not connected to the #88 bulb in any manner.

lelshaddai
03-10-2018, 09:43 AM
Unfortunately the 88 bulbs I find are 6v. Will a number 1076 12v bulb work? It is single filament, dual contact.

52-fan
03-10-2018, 10:13 AM
I am hoping you get an answer. I face the same thing with my 52. It has been converted to 12 volt negative ground also. I tried to install a 12 volt bulb in the dome light and it immediately blew out. The map light on the dash works with the door switches. It has been low priority, but I want it fixed right.

lelshaddai
03-10-2018, 11:04 AM
52-fan, I have the map light working but had to use plastic bolts so it would not ground. It has a dual filament bulb(stop light bulb) in it.
The dome light works with a dual filament but the housing grounds and constantly lights up. The 88 bulb suggested is 6v, I am going to try a 1076 bulb. I am also trying different ways to not have the dome housing and cover to not ground. When I have the housing hanging unattached it works perfect with the switches. The bulbs should not care about positive or negative ground, that is what I was told. At least my light did not care. I hook the wires both ways and it works the same.

52-fan
03-10-2018, 11:58 AM
I will have to get my wiring diagram and trace the system. It has not been very high on my list, but just one more thing that will give me satisfaction when fixed and no one else will notice. ;)
I have considered changing to an LED for my dome light.

TWChamp
03-10-2018, 12:18 PM
Unfortunately the 88 bulbs I find are 6v. Will a number 1076 12v bulb work? It is single filament, dual contact.

I thought you had gone back to the original 6 volts. I'm not sure what the same bulb would be in a 12 volt style, but make sure the base of the bulb has no connection to the filament. A dual filament bulb won't work, as the base is the common ground for that style bulb. From what you say, it sure sounds like the wrong bulb is your problem.

StudeRich
03-10-2018, 12:29 PM
You need a 1004, if going with 12V, it's a DUAL CONTACT, Single Filament as mentioned in Post #3.

These have the elongated Glass Bulb with straighter sides not rounded type like the shape of the common 1157.

lelshaddai
03-10-2018, 01:02 PM
I will get those and try it out,
thanks

lelshaddai
03-10-2018, 02:18 PM
Thank you rich, those 1004 bulbs solved the problem. 52-fan, you might want to try this first.

52-fan
03-10-2018, 02:23 PM
Thank you rich, those 1004 bulbs solved the problem. 52-fan, you might want to try this first.

When I get back to it, I'll try one of those. I need to do some checks of the wiring too. The main harness is new, but I'm sure the dome light wiring is original.

gjamesk
03-18-2018, 01:17 PM
I have considered changing to an LED for my dome light.
Don't do it! I can verify that a dual contact LED will NOT work in this application. Thought I'd be smart and update to LEDs when rewiring my 52 - the interior light circuit would not work at all. Replaced them with 88 bulbs and all is good.
Also, I didn't have any luck with LEDs for the tail and front parking lights as they did not work correctly with the turn signals. Worked okay as long as the lights were off, but with the lights on I had all kinds of weirdness. Replaced with standard bulbs and that fixed it. This is with an electronic flasher and LEDs supposed to work with 6 volt positive ground.

52-fan
03-18-2018, 03:32 PM
Don't do it! I can verify that a dual contact LED will NOT work in this application. Thought I'd be smart and update to LEDs when rewiring my 52 - the interior light circuit would not work at all. Replaced them with 88 bulbs and all is good.
Also, I didn't have any luck with LEDs for the tail and front parking lights as they did not work correctly with the turn signals. Worked okay as long as the lights were off, but with the lights on I had all kinds of weirdness. Replaced with standard bulbs and that fixed it. This is with an electronic flasher and LEDs supposed to work with 6 volt positive ground.

My car is now 12 volt negative ground. I may not change the dome light to LED just because I really don't need extra light in the back.