GT Dome Light wiring question

I'm about to reinstall my newly upholstered hinge cover interior panel but before I do I want to mount the dome light to it and wire it in. I have the light fixture but can't seem to find the wiring for it? My guess is that it was cut / removed some time ago.

I know that they don't do much as far as lighting but it bothers me when I see the door switches knowing they don't do anything.

How were these wires run for a 1970 GT? (ie under the headliner? under the car & up the C pillar etc ????)

PS I also have new door switches which will get replaced / rewired too.

Tim, there is a wiring harness that runs up "through" the C pillar and then to the dome light. If my memory services me right, the wires are Purple and a Green/Black wire, so it is a very "skinny" harness and should be covered with black tape. The harness plugs in on the floor back by the right rear taillight. The purple wire goes to the switch for the hatch (If you have one) or directly to the dome light. The other wire is for the rear window defroster.

Perfect!

Thanks Gary. At least I know where to start looking.

On the 70 GT the dome light works off the door switches. The map light on the radio console only works with the map light switch on the radio console. I also have a 70 gt. I don't have a switch on the hatch, do you? I know the hatch was replaced with an earlier model hatch, so mine dome light will only work if one of the front doors is opened. I put 2 little lights on the top of the kick panels that also work off the map light, to give some light in the foot wells.
Ken

Hi Ken,

Gary is refering to a third door switch that is mounted up on the right by the hinge. I don't have a mount for said switch but the hatch (probably not correct model year) has a tab that is intended to push it in if it were there.

I did buy three door switches for this project so I may make the missing mount (seems easy enough) and wire it in.

My 70 GT also has the wire running up the c post from the right taillight. There is no hatch switch but the tap is on the door for it and I assumed it was from a later car. I removed the body side of the mount and switch from a 71 parts car but never installed it. The dome light also has a switch to turn it on at the light. I ran an extra wire up to the light for a third brake light that I installed later.

Okay, I've read all these. My 1970 GBT's rear hatch does not have a light (maybe it used to at one time), but my driver door has two switches that depress (one metal and one plastic). I think the metal one is for the dome light, but not sure what the other is for. The PO updated a lot of things, so maybe he left this out. A 1970 is supposed to have a switch on the lrft side of the steering column to turn of the dash lights, but mine does not. He must have replaced tha housing with a different year. Also, I do not have a rheostat for turning down the dash lights, as if I would want to do that, nor do I see a place on the dash where one was previously installed. Did all MGB's have these in 1970? I just don't see an extra hole anywhere! Not worried about it, but would like the dome light to turn on when I open the door. There are two wires under the base of the light, but not sure how to wire it correctly so the lights turn on with the door switch. There is power there on the green/white wire so I inserted the spade into one end of the bulb holder and the other end is grounded. The light turns on when I slide the switch connecting ground to power, but not sure where the other wire goes. It doesn't have power in it. Is this the wire that comes from the door switch? Maybe my door switch is not working, as when I was trying all this, I had the door open. The wire I am not using also has a spade connector on the end of it. Just curious. If anyone wants to unscrew their dome light base to see, it would help a lot!
Thanks-
Dennis (in Dallas)

Dennis, I will attempt to help you, line by line.

Okay, I've read all these. My 1970 GBT's rear hatch does not have a light (maybe it used to at one time) It should have had one mounted to the covering/fairing that runs across the rear of the interior roof panel and covers the hatch hinges. Under that fairing, there should be at least the remnants of the wiring for that "dome" light.

Thank you for all that good info! It all makes sense and I will try it. When I said "spade connector: I meant the Lucas bullet type connector. I'm still learning... The Dome light assembly I got is from Moss, but looks just like your picture. When I said a "green" wire, that was from memory. I'm going out to the garage and checking it all out and will report back later! You're a HUGE help. That wiring diagram makes a lot of sense. I know what to try. I think the two wires are original, not a rewired job by the PO. I probably got the wire color wrong. As far as your '69 not having a rheostat, my 1970 was built in 10/69, but has the split rear bumpers and the VIN number is a 1970

VIN: GHD5UA188O88G
Build Date: 1969-10-29
Original Colour: Blue Royale
Current Colour: Blue Royale
Odometer: 52265 miles
Body Code: GHD5UA188O88G
Engine Type: 1.8L 4 Cyl 5 Main B-Series
Engine Code: 8GF WE H 8818
Transmission: 4 Speed

Magic VIN Decoder
Assembly: Abingdon, England
Make: MG
Engine: 1400cc to 2000cc
Body Type: GT or Coupe
Series: Mark III (1970-1979)
Market: USA, Left Drive
Model Year: 1969 to 1970
Car Number: 188 (an early 1970!)


Thank you sir.
Dennis

Here you go, Dennis. Hope this helps.

Thank you Bob. I wired it that way last night, but no luck, as far as off/on with door. I will recheck everything and try again. I do appreciate the schematics and photos! You're a terrific help!

Dennis


> Below: My LBC being prepared for me last May...

If you have an ohm meter, check and see if one of those wires is actually grounding when you open the door. You may have a loose connection somewhere.

Well, my dome light is working fine and I figured out why it didn't turn on when I opened the doors... the 40 year old switches were the problem. I loosened the driver's side switch's screws and pulled it out to look at the wire, etc. The plunger piece the door pushes in does not slide in and out good at all and even when the door is open, the metal tube piece that goes in and out that holds the wire when the door opens/closes does not come forward enough to contact the steel body (ground). I cleaned the parts with a rag that had some WD40 on it, as it was dirty, but it didn't help. But when I manually touch the side of that part to the edges of the hole where it all goes into, as if the door was open, the dome light comes on, and it turns off when I don't touch ground with it, so that switch needs replacing I guess. When the switch is screwed to the door jam tight with two screws as it should, the wire ho;der tube doesn't make any contact with ground since it doesn't come forward enough.

On the passenger side, I loosened the two screws and pulled out the switch and guess what?? No wire attached at all! It was just a switch screwed into the door frame hooked to nothing! Not sure where the wire is, but not worth tearing everything apart just to fix a weak light.

When I slide the little sliding switch of the dome light assembly over, the light comes on fine, so for now that's fine.

I would have to go back to make sure, but I think my wires were reversed from the picture you sent me, Bob. It didn't work as in the photo, but when I attached the purple/white wire over the ground wire/copper plate and the solid purple (HOT in my case) on the other end, the light csme on using the switch. Before doing that, when I quickly touched the solid purple wire slightly to the ground side, it sparked and made a sizzle sound, as if it was a short, so I didn't attach it there and didn;t try ot sgain. And yes, my car is negative ground... hmmm. Maybe 40 years ago when it was originally wired, it was lunchtime and the bloke doing the wiring was in a hurry to finish up and join his mates for some bangers and mash! Anyway, other than the door awitches, everything's fine and no fuses were blown. When the light switch was slid to "off", but I simulated the door opening by hand, the light went off and on as it should. Does it mnake sense that the solid purple wire is the hot wire here? Funny that it was opposite to the picture you sent Bob. I'll look at the 1970 schematic and see what it says.

But that's the fun part of owning and working on these little cars. No printed circuit boards or fancy electronics! It's kind of like doing stuff in electric shop when we were in school! Imagine, a switch that slides back and forth - or in and out to make contact with the steel body to complete a circuit! How quaint and simple!

Thanks to all that came forward with suggestions, especially Bob!

Dennis

Below: My engine was completely taken apart, cleaned and rebuilt, with heads and valves polished and cylinders bored .40 over. Here my man Chris is installing the new cam with fantastic mid range that has a lot of torque and great pickup.

The plastic switch on the drivers side only is the "key in" switch warning system. There is a wire from the ignition switch that is grounded when the key is in the switch in the off position. If you open the door you complete the ground to a buzzer that is located behind the console above the tunnel. The buzzer has a always hot wire on one side and grounds through the switch. It was common practice to disconnect the buzzer. I used the switch and buzzer to make a headlight left on buzzer.

Pull the bullet on the ign switch side of the door switch and run it to ground. Connect the hot side of the buzzer to a red wire behind the console. Now if you open the door with the "Lights On" a buzzer will sound. The beauty of this is there is nothing to buy and no wires to cut it is all done with bullet connectors.

That's interesting Gary. I do have that extra plastic push switch on my driver's door jam above the dome light switch (that needs replacing), but didn't know what it was for. When I get a chance, I'll look behind the console for the buzzer iof that's where it is. Under what tunnel? Is it inside the car or underneath the car? I don't think I'll be leaving the key in, but why not make the plastic switch do something useful? Or I might use the switch to turn my dome light off and on, if possible. These little cars are like working on a big toy that the PO put together from a kit that came from England and now we have to fix the wires, since either he didn't do them right, or they have an age problem! On modern day cars, we can't have ANY fun doing anything with them or to them! That's why these little British cars will be around for a long time, because of all the parts available from Moss, VB, wrecking yards, buying or finding a donor car or looking eBay! Other than having an electronic ignition, if you do, NO TRANSISTORS! What a throwback!

That would make a good slogan for an MG shirt...

[sub]MGB LOVER... NO TRANSISTORS REQUIRED![/sub]

Dennis

I reread your message and see you explain how to make it buzz when the lights are left on! That's very different! Thanks... that's very useful and worth checking out.
Thanks!
Dennis

The buzzer is inside the car ,,,,

"a switch that slides back and forth - or in and out to make contact with the steel body to complete a circuit! How quaint and simple!" Simplicity is sometimes more reliable and longer lasting than technologically advanced. The switches on my GT are 42 years old now. Worn, but not beat up and probably dirty to some extent, but not so much so that they aren't able to do what they were intended to do. Electronic switches on the Audi we had, however, were just a little too high tech and we replaced several in the 5 yrs we owned the car.