Interior light wiring

I'm trying to understand my interior courtesy lights (GTS has one in each foot well) and see if they are working correctly. Judging from the wiring diagram and the rocker behavior of the switch, each switch has three positions - off (middle position), switched to door open (one side), and always on (other side). The first two functions work fine, and looking at the light switch body, it's pretty clear how the electrical pathways work. The third always-on function doesn't work on either switch though, and I'm at a loss to see how it could work given what the switch looks like. I see only two available wires to connect - one's power and one's a ground that's controlled by the door pin switch, interrupted when the door is closed, and grounded when the door is open. I assume I'd need a way to have the ground side of the bulb always grounded when the switch is rocked to its third position. Also, there's a third spade terminal on the switch which has nothing connected to it - not sure if that's significant, but it doesn't look like there's any way that terminal can connect to the ground side of the bulb anyway.

Can anyone explain to me how the always-on function works on this switch?

 

Sounds like a wire to ground is missing on the third terminal, that would be logical based on your description of the setup. Any chance a previous owner removed that wire because he had his battery run empty by accidentally leaving the courtesy light on?

 

That would seem logical, except that the third terminal on the switch doesn't appear to connect to the ground side of the lamp in any way controlled by the third switch position, nor is there a ground wire floating around behind the trim panel where the light sits. It's pretty strange.

 

Just had a look at the wiring diagram. The courtesy light receives permanent plus from the battery (marked red), ground via the door switch (marked green) and permanent ground. The unused third terminal is for the off position, so the switch would have four terminals with three wires (plus, door switch, ground) connected.
The old Hella interior lights had a spring contact at the side providing the ground connection for always on but not sure from memory if that type was used in the GTS. Could you post a photo of your switch?

Do you have a multimeter at hand for testing the switch states?
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The wiring diagram is slightly misleading, in that the center position of the switch is the "off" position, and appears to be implemented by cutting continuity to the power side of the light. I'll remove the switch and photograph it tonight. I'll stare at it some more as well and see if any insight arrives

 

Don't worry about the switch position in the wiring diagram, the guy drawing the diagram probably went that way and in the production kickoff Ferrari changed the switch positions due to a different switch type or usability issues. Looking forward to the photo to solve the mystery

 

I figured out what was going on. Two problems - first, the switch wiring was connected backward. In the photos, the orange wire is where I found the red supply wire, and the black wire is where I found the ground wire that connects to the door pin switch. The wiring should actually be the other way around, with the supply wire always connected to a bulb terminal. Then the other bulb terminal is connected to the door pin switch ground when in the right rocker position, completely disconnected in the middle position, and grounded to the switch casing in the left position. Which leads to the second problem, which is that the casing ground terminal wasn't connected.

So now I only have two more problems to deal with. One is that the switch detent that controls the rocker position is broken. The other is that the switch casing ground wire is missing. Any ideas on how to correctly remove the trim panel that the light casing sits in, and where the ground wire should attach? I assume there actually is a ground wire, right? Because the switch casing sits in a vinyl covered trim panel that isn't grounded.

Isn't electrical wiring fun?
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The crimp connector with the blue plastic is a newer modification, maybe someone dropped the ground wire behind the vinyl when working on the wiring? Any ground connection connected to the chassis should do the job if the original ground wire stays missing.

 

I've repaired these and will try to help. There is a captured ball and spring you might want to inspect, perhaps also lightly lube the pivot points. I guessing as I haven'treal;ly seen them but mine had failed the same way.

I've gone to local VW dealers (Campbell-Nelson) and held an old one and said I needed the same and used is OK. They led me to a discard box where I could cherry pick some old ones and gather parts I needed. Might want to try that for a low cost replacement if you don't want to tinker (I am a tinkerer)

Scott

 

I inspected the broken switch. Any repairs to the ball-and-spring mechanism look like they would be difficult - it's a very tight area, hard to see what's going on. I just bit the bullet and ordered a NOS replacement switch.

 

Wow, now I see they're $100 each.
http://www.dinoparts.eu/EN/ferrari-246-gt-gts/lights/door-interior-lights/interior-light-black-body-.html
Next time give me a shot at it, don't mind helping while I have time now.

Scott

 

The one on mar3kl's photo looks like a Hella 2JA series interior light to me. Hella is still producing many of the older styles and most of these have a street price of €15-50.
If you can find the product number (00x xxx-xxx) somewhere on the original interior light then it shouldn't be too difficult to source one if they are still produced.

The two on the dinoparts website don't look correct to me, they have the pivot points in the middle whereas in the photos from this thread they are at each end.

 

Well, the replacement switch arrived today and sure enough it doesn't look like the original. I'm going to return it, but now I need to repair the broken detent on my switch. After cleaning it up, I found the spring was still wedged in there, and all that's missing is the detent ball - anyone have ideas on where to find a replacement? I'm thinking a ball bearing of maybe 1mm diameter should do the trick.

 

The Ferrari (Hella) courtesy lights on 246's and 365GTC4 lights do not have the extra ground wire on them, because they are only meant to come on with the door open. Originally Ferrari locked the lights in the (on with door open position) by drilling a hole in the side of the metal rim and screwing a sheet metal screw into the plastic lens to keep it from moving. The lights are the same as early Porsche 911, but it is hard to find them with a chrome surround these days, as Hella changed the surround to black.

Brian Brown
Patrick Ottis Co.

 

The Porsche part number for the light is 90163210300, but most suppliers only have the black rimmed light.

Here is a supplier with the chrome rimmed light:
http://www.design911.co.uk/fu/prod4165/Interior-Light-Chrome-Edge-Porsche-911/

 

I found the original number, it is Hella 2JA 001 355-001. It is listed in the 2008 Hella catalogue but not in the current one anymore, might be EOL.

Some more OEM numbers when searching for one:
MAN 81.25201.6043
Opel 12 30 726, V29605810
VW 815 947 105

Lowest offer i have seen was at €25 including taxes from an austrian online shop.

 

Thanks for the pointer to the Porsche site. BTW one of my switches has a working detent, and after cleaning the switch contacts thoroughly and swapping the backwards wiring it now works correctly in all three positions. I guess the trim panel the switch sits in must be metal, allowing the always-on position to ground through the switch casing.

 

Mark,

How about $25 plus your core and I'll swap you a used, fully functional extra one I have?
Several of us are driving our Dinos for Monterey in a few weeks, might be able to deliver it to SV if you can wait that long.

Scott


PS - I have one spare that is not marked Hella but BOM in a square cross logo pattern - anyone ever heard of this ?

 

Synchro, you have a PM

 

The foot well lights on my '74 GTS are BOM lights not Hella. Look very similar but I don't think they are a rocker switch. At least they are VERY resistant to rocking. Don't like putting too much pressure on Italian plastic! 99.9% they are original. Maybe Ferrari used more than one brand.

 

Rutlands has the same part available as on my car. Ferrari part #20144309. Not cheap but the real deal.

 

My BOM is a rocker and rotates exactly like the Hellas, but cosmetically the 4 chrome curves are slightly more square-ish than the Hellas and one electrical connector points at a different angle.

It needed some cleaning up to rotate smoothly, but these probably go for years without being touched

 

PM sent back to you

 

The last photo shows a third terminal on the chrome casing offering another path for operation in the switch rocked to the "Far position". If this is tied to ground then that would provide the constant ON position while the rotated "Near" position allows switching through the door jamb pin switch and the "Center" position is off.

As stated above the Dino doesn't have wiring to use that Far position but you could easily add it if you desire.

 

Believe it or not the far position actually works - my guess is the trim panel is metal and the switch case grounds to it when clipped in. Can't see inside, but that must be what's happening