Dome light wiring - 512TR

So here's what I was able to come up with while researching the same problem for a different thread (it's way down on my to-do list, so I haven't followed up).

Based on the Testarossa wiring diagrams, and me digging around in the car ('90 US Testarossa), here's what I think I understand is going on for my car:

C8 pin 4 supplies ground to light the dome light via two purple wires, one from each side of the car. This pin will be at ~13V (through the filaments of the door lights) when the door is closed, and ~0V when doors are open (confirmed on my car only with the functioning passenger door). See the paired purple wires on the left side of this pic:
http://www.ferrarichat.com/forum/showpost.php?p=139070223&postcount=21

On the driver's side only (passenger's door is wired differently), according to the pre-'88 wiring diagrams, one of those purple wires leads directly, with no breaks or connectors, to the driver's side pin switch, which has two wires (purple insulation but with a thin black paint coating that scrapes off) connecting at its single terminal, as shown in the following pic:
http://www.ferrarichat.com/forum/showpost.php?p=139072128&postcount=24
(look closely and you see two wires leading away from the crimp connector, then getting encased in heat-shrink tubing - one wire has a scrape showing the purple color)

I still need to look at the current '88 wiring diagrams, but according to the older diagrams that should be one solid wire. Something is fishy, because mine, like yours, has no continuity between these two points.

 

Can't wait to hear this, as this was/is the identical situation I have with my 512TR.

 

Yes. If you ground this pin you will see the dome light, the door puddle lights and door marker lights come on (only on the passenger door for me in the current condition).

My pin switches only really have one wire contact, with the other side grounded by mounting against the body. The "+12" side is hot through the filaments of the marker and puddle lights on that door (and if correctly wired the other door and dome light).

If you only have one wire on that hot side, then it's different than mine.

BUT, it did get me looking at the diagram again and it turns out I had misread the diagram and was totally wrong about the connection from the driver's side pin switch. The driver's side pin switch connects to C8 pin 4 via a split at C1, similar to the setup of the passenger side. Here's what happens: one of the two wires from the pin switch (in my case) leads down to C1, the connector for the driver's side door accessories. On the "car" side of this connector pin #9 will have two wires crimped into it, one from the pin switch and one leading directly to C8 pin 4, with no interruptions.

I've never seen C1 (or C9 on the passenger side), so I don't know how bad they are to access.

Based on the fact that my door lights do correctly function on this side, it's a break somewhere between the crimp at C1 pin #9 and the crimp at C8 pin #4, inclusive, for me.

Sorry for adding to the confusion!

Again this is all based on the pre-88 diagrams I have available at the moment. I would love to see if there are changes for newer models, as this exact failure seems to be far too common and consistent to be explained by my current understanding of the wiring, unless maybe there's some specific mechanical strain on that side of C1 due to frequent door usage on the driver's side.

 

OK, I confirmed in the '88 US Wiring (for my Testarossa) that the wire from C1 to C8 should be uninterrupted - no connectors, fuses, breaks, etc. Though it does claim to be black (N) at both C1 and C8, and both wires to my C8 pin 4 are clearly purple, and the wire from the door pin switch towards C1 (a connector I have yet to find) also appears to be purple. Don't know if there's any indication of how this wire is actually routed.

So assuming that your driver's side door lights work (puddle and marker) and that the 512TR circuit is wired like the Testarossa, this would indicate that there's a break somewhere between C1 pin 9 (which must have a good connection to the pin switch to run the door lights) and C8 pin 4. Which should otherwise be one solid wire between the connectors.

Would sure love to check out C1 at this point, but I've never had my dash off and there didn't seem to be anything accessible otherwise. C1 is claimed to be "on LH side of dashboard."

 

I'm following up in my previous posts on this topic to add some new information. My goals here are:

1. Provide further documentation for those like me trying to figure out the door switch/dome light system or problems in the future (I didn’t even know where the connectors were).
2. Review the way the system is actually wired in my 1990 Testarossa and point out the discrepancies with the claimed wiring in the 1988 wiring diagrams.
3. Hopefully draw out more knowledgeable sources to provide more pertinent information.
4. Provide what I think is the easiest/quickest solution (hack) to getting the driver’s side door switch to light the dome light, for those with this same problem (passenger door lights the dome light, driver’s doesn’t).

Sorry, it’s probably going to be pretty long, rambling, and painful, but I was up until 3:00 this morning dealing with it, so that’s where my head is. I’LL PUT THE PROPOSED SOLUTION IN A SEPARATE POST for those who don’t want to cut through all this junk.

In the system at its most basic level either pin switch will close when a door is open and provide a ground to light the dome light, puddle lights, and marker lights, which already have constant 12V on the other side of their filaments. The way things SHOULD be wired, according to the Ferrari diagrams, this ground signal is shared between all of these lights (the two in-door lights for each side of the car and the dome light) and the two pin switches, so that activating either pin switch will light up all 5 lights (as Shamile demonstrated in another thread, http://www.ferrarichat.com/forum/showthread.php?t=261084).


So here’s the details on how the passenger side is wired on mine, demonstrating the way the car SHOULD be wired according to Ferrari:

The passenger side pin switch (see pic, light switches are the top switches for my 90) has one tab off the back which, when the door is open, will provide ground (from the frame of the pin switch) to power the lights via a single violet wire leading towards C9. This wire is labeled as N, black, in the diagrams. And note that the driver’s side will be different as it should have two wires leading away (more later).

C9 provides a connection from the car to the electronics in the door, and is conveniently located under the passenger side hood latch, just pull back the carpeting (see pic). At C9 the ground signal from the pin switch will split to perform two different functions:
a. On the “car” side of the switch the violet wire (again labeled N, black, in the diagrams) from the pin switch arrives on pin 9, and a second violet wire is crimped in to the same pin, leading off to C8 (towards the dome light).
b. On the door side of the connector a wire will lead away to provide ground to power the puddle light and marker light.

C8 provides electrical connection from the rest of the car to the area of the dome light. It is located under the dash above the passenger speaker (see pic).

At C8 grounding signals from both doors are brought together to lead to the dome light. On the “car” side of the connector, the two violet wires (again labeled N, black), one from C9 above and a similar one from C1 on the driver’s side SHOULD come together at pin 4. You will see two violet wires in the picture, and one of these is indeed connected to C9 pin 9, as it should be. On the dome light side of the car, a wire continues on to provide switched ground to power the dome light. Other pins provide power, and continuous ground for manually illuminating it via the dome light switch.

--------

OK, so the driver’s side SHOULD follow basically the same motif, and provide the other violet wire (again labeled N, black, in the diagrams) to C8 to power the dome light from the driver’s side as well. Here’s what the actual wiring in my car is:

The driver’s side door pin switch (see pic) should be and is wired slightly different from the passenger door, as it has two wires leading away, one to C1 (same function as C9 but for the driver’s side) and one leading to an unnamed connector for the ignition key switch, which I have not yet looked at (more on this later). Again the manual labels these two wires N, black, but they are really violet with a black stripe on this side of the car, though very dirty in this locaion.

C1 performs the same function as C9 on the driver’s side, connecting the driver’s door electronics with the rest of the car. It is underneath the driver’s side hood latch, just pull back the carpeting (see pic). In the same way C9 is wired, the car side of the connector SHOULD have two wires crimped in at pin 9, one coming from the pin switch, and one leading off to be the other of the two wires at C8 pin 4 discussed above to provide ground signal to the dome light from the driver’s side.

What my C1 ACTUALLY has is a single violet/black wire (should have been N, black) coming from the pin switch, with nothing leading away to C8 pin 4! So, at least according to the Ferrari diagrams I shouldn’t even expect to have my driver’s side pin switch power the dome light! There’s not even any trace of another wire (hopefully a violet one) anywhere in that part of the harness.


So after all that clearly there’s something wrong here. Certainly there is at least the second violet wire at C8 pin 4 to account for, the one that should be coming from the driver’s side, that could go somewhere. So I can see a few possibilities.

1. Ferrari just didn’t care about powering my dome light from the driver’s side, and it’s never worked, and they just ran that violet wire out somewhere and let it dead end (hoping that’s not true).
2. Instead of providing the connection from the pin switch to C8 pin 4 via an interconnection at C1 pin 9, they chose to utilize the OTHER violet/black wire, which according to the diagram should lead to an unnamed connector for the ignition key switch unit. I have yet to look for this connector, but I’d expect to see one violet/black wire and one violet wire crimped into an unspecified pin on this unnamed connector if this was their plan.
3. That violet/black wire doesn’t even go to the ignition switch connector, and is intended to mate with the violet wire leading to C8 via some other way.

In the end the issues of 2 or 3 are interesting, because from what I believe the wiring diagram is saying this second violet/black wire (again labeled N, black) is intended to run a light within the ignition key unit when the doors are opened (to help you find where to put your key at night I guess). I fail to see how my ignition key assembly could light up in any way. So maybe it makes sense for them to use this “unused wire.” But still, it starts off at the pin switch violet/black and the wire going to C8 pin 4 is violet only. So if it ever worked at all they must have been connected in some way.

In the end it’s more of an academic question now, because I don’t need mine to be perfect concourse condition, and I think that there’s a fairly clean and simple fix after having finally found the location of all these connectors (posted in a separate post to save everyone having to read all this stuff).

But I’d love the input of anyone who knows the real story here.
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The proposed hack solution, at least for my 90 TR:

So after all that digging, I think that the simple solution is to just run a jumper wire from the purple/black wire at C1 pin 9 to one of the purple wires at C9 pin 9. There is very easy access to this entire area, and it can be very neatly routed and hidden entirely underneath the Velcro’ed carpet, sneaking it behind the intake for the environmental system. This eliminates having to remove the entire dash, as I believe Jimbo had to for his fix.


Again, this should solve the problem with the following symptoms:
1) Pin switch on passenger side correctly lights the in-door lights and the dome light and,
2) the pin switch on the driver’s side correctly lights only the in-door (marker and puddle) lights.

I tested it out very late last night (well, early this morning) and it was great having the dome light (dim as it is) when I opened the driver’s door! In deference to the Ferrari diagrams, I’m going to plumb this in with a black wire when I install it permanently, since pretty much none of the wires they labeled as black actually were.

 

Thanks James. Hope this 'fix' stays fixed. Now, you just need to update your dim dome lights with the Bullfighter special! Oh, the trouble we go to just to see something when the driver's door opens!

 

Sorry, I should have put a disclaimer not to get your hopes up on any possible similarities!

Just in case there's still some family resemblance, I can tell you that while the connectors are pretty visible there (otherwise I'd have missed them), where the harnesses enter the car are more hidden. Maybe there's a chance the connectors are more neatly hidden but you can trace the harnesses to them. Because it's too hard to photograph, I'll try to describe it like this:

On the "door" side of C1/C9 the harness enters laterally right pretty much right underneath the lower corner of the windshield. It's pretty much impossible to get a hand down there on the driver's side, but on the passenger side I can reach in and feel it enter. The "car" side of the harness reenters the car laterally at the box for the environmental system (don't know what to call that).

Sorry I don't know how to reach the pin switch, as it seems heavily buried in my Testarossa. Pretty much it doesn't look like there's any access into this void underneath the quarter panel from the area under the dash, which is why they routed C1/C9 up through the baggage area. Obviously this could be different for yours.

But now that you mentioned more about the key switch I really MUST to know more about the location of its connector. Not only could this help solve a riddle about the connection to C8, but I need to use the voltages up to the buzzer for other diagnostics (I still have no idea how I could have a light at the key switch, but I hadn't even thought about the connection between the door switch and the buzzer!).

Oh, and like I said, take those wiring diagrams with a grain of salt! Mine too claims that there's a wire coming from C1 towards the rest of the car. But I'll be interested to check on the window ECU. Fuse box work is this weekend.

Oh, and I'll spare you pictures of my dome light working with the driver's door open tonight...

 

OK, it's tomorrow now. Had to use a little artistic license on pic #2; since the dome light is obviously not bright enough to illuminate anything in the interior, I added some lighting to prove it was really the side with the steering wheel.
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SHOWOFF!

I suspect your passenger door is ajar.

 

....bawhahahaha


Shamile

Freeze....Miami Vice !

 

While trying to figure out how get the light for this shot I did think about pressing the button to turn on the map light, and it dawned on me I could just have pressed the dome light button too and have saved all that work. Guess I'm just not that smart, which would help explain my owning the thing in the first place.

I still haven't had a chance to drive the car yet and use the light in a real-life situation. I'm itching to get out to test that and my newly "machined" starter solenod.

Yes, now that it actually comes on when getting in the car it's painfully obvious how inadequate it is. I basically learned a couple things:
1. I need to do something to improve the dome light.
2. I need to clean up the ancient mouse poop that's near C1.

But there is something perverse in using 5 kW worth of bulbs to yield 0.5 candella of illumination in the car. I'll have to review the threads and figure out the best way to make it slightly better while still remaining tastefully near stock (i.e. poorly thought out).

While I'm trying to avoid whatever mental image is lurking under the surface there, it would be good to get Mr. Miami Vice behind the wheel of a proper white Testarossa for a change. Sonny Burnett is going to bust in and revoke his '80s license pretty soon.