i think i screwed something, but dont know what.
I was in a process of ordering led lights for the interior lighting, so i was trying to measure the distance between the 2 prongs of the dome light, it shorted and blew the fuse.
the light was on door (middle) position and the bulb was out.
The front map light and the door light also stopped working.
i found the 7.5A fuse blown, on the passenger side, #11. replaced it, and the front map light and door light started to work, but the dome bulb is lit with all the doors closed. it is dim but lit up.
i measured the voltage and got 3v when it is on the door (middle) position.

is there any fuse/relay that is stuck and forcing the dome light to light up, in the door position, with all the doors closed.

 

Also i measured the voltage on the 2 pin connector of the dome light, and there is continues 12V with door open and door closed. i dont know what it should read before and after

 

door switch or the switch at light itself got torched during testing

We have a list of LEDs for every light, ck the diy section

 

how to check the door swtiches?
i checked the light switch, it looks ok. all the contacts are clean...

can anyone tell me if the 12V should be on all the time at the 2 pin plug?

 

there is a push button switch on the B pillar that tells the car the door is shut
look near rear corner of door to car area

 

i checked all the switches, as they light up in the dash. all the doors switches are working.

any other suggestions?

 

Just so we are clear when you say dome light are you talking about the light behind the sun roof or the light between the sun visors?

 

Check the pins 1, 1', and 2 (blank squareds). Make sure they don't have power when they are not suppose to. If there is power when they are not suppose to, then it's shorted/defective.

You might be able to fix it. Look at the circuit... shorted... touching each other.

Note: This lamp is behind sun roof.

 

Yes i am talking about the lamp behind the sunroof.

i did the continuity check as per the manual, but did not check power between 1 & 2. will do that today.

i think the only time there should not be power is in OFF position, and in MIDDLE position when door is closed.

i found the switch very simple, and has no circuit. it is only connected to 1', when its on OFF, it shorts 1' & 2 in the MIDDLE position, and it shorts 2 & 4 in the ON position.

 

You should have batt. voltage at the white/blue wire all the time. The fixture grounds the black/white wire through the pass. side multiplex control unit. It also grounds directly when it is switched to on.

 

i havent checked the wire colors, but i assume you mean the 2 pin socket that is connected to the light fixture.

So if there is power all the time at the 2 pin socket, when i move the switch from OFF to MIDDLE position, it shorts 1' & 2 creating a complete circuit (through 1 & 3), and the bulb lights up regardless of the doors open or close. and then i move the switch position to ON, the switch shorts 2 & 4 , which again completes the circuit (through 3 & 4) and the bulb lights up.

i need to know where is the door open/close signal processed which will stop/start power at the 2 pin socket.

I could be wrong here, but this is what i understand.
Correct me if i am wrong.

 

Nothing starts/stops power to the fixture. Power is supplied to one side of the bulb all the time. The door switches signal the passenger and driver side multiplex if they are open or closed. Left doors go to the driver multiplex; right doors go to the passenger multiplex. The black/white wire that supplies ground to the fixture, goes to the passenger multiplex. When the passenger multiplex grounds that wire, the light comes on. For what it's worth, the wiring diagram shows terminal 3 as power, and terminal 1 as ground. Disconnect the fixture and see what you've got at each terminal.

 

^ that's what's weirded. So something is grounding it off. From the dimness of the light it seems like a multiplex to me. However, a shorted dome switch would do it too but at full brightness or not... depends on contact.

OP... Just replace the dome light with test light. If test light is lit then you have a short. If not then you are done. Replace switch/dome light.

 

^ that's what's weirded. So something is grounding it off. From the dimness of the light it seems like a multiplex to me. However, a shorted dome switch would do it too but at full brightness or not... depends on contact.

OP... Just replace the dome light with test light. If test light is lit then you have a short. If not then you are done. Replace switch/dome light. With the doors close.

 

^That's what I'm guessing. I suspect the 3 volts he was talking about is on the ground leg (one of the multiplexes) giving at best, 9 volts across the bulb.
It's been a long time since I've had to replace a multiplex, but a few on here have had to.

 

thanks for all the suggestions.
i will try this today and post the results.

 

ok. i did the tests.
first i checked all the door switches, and all of them go ON/OFF on the dash, when they are OPEN/CLOSED. including the trunk.
does the hood have a switch? because thats the only one i did not see a light come on in the dash.

There is power all the time between 3 and 1, and 3 and ground screw. when i check continuity between 1 and the ground screw, i read 510 ohms.

the big problem i found is the test sheet. i think the numbers 2 and 4 are swapped in the diagram. which means in the diagram, on top it should be 1' 4 2 and not 1' 2 4.
check the first video where i checked the switch in both the positions, 1' 2 4 and 1' 4 2 , and only the later worked.

as you can see in the in the second video, when the switch is in off position, there is no continuity between 3 and 4. but if i swap the numbers 2 and 4, there is continuity between 3 and 4.
when i move to switch to middle position, 1' and 2 are shorted, but as per the sheet the there should be continuity between 1 and 4 and 3, and this can only be achieved by swapping 2 and 4. And when the switch is in ON position, 2 and 4 are shorted, so even if we swap 2 and 4, the test would be correct.
can can someone confirm this that the test sheet diagram is not correct.

and in the third video, you can see how the light goes dim at the middle position.
below are the voltage measurements

 

If you want to use the factory diagnostic method, do it the way the factory describes. That involves removing the housing and disconnecting the connector. Then check continuity with the ohmmeter on your meter. Or you can ground the negative lead on your voltmeter to a known good ground, and check the voltage at the both pins on the connector with the housing still removed.

 

i did both ways.
as per the manual, removed the housing and disconnected the connector.
And checked it with the housing connected.
the 3 videos shows it all.

 

With your voltmeter negative lead attached to a known good ground, what is the voltage on the black/white wire with the housing disconnected? (with all doors closed)

 

Checked the voltage, it reads 0V.
And good ground to white/blue was 12V.

Can you comment on the diagram? should the 2 and 4 be swapped to get the proper continuity reading.
my concern is, in the middle position, 1' and 2 are shorted and in ON position 2 and 4 are shorted. so electrically how does that play out.

 

That makes sense. #2 is the manual on pin. So if '1 and 2 is short then the lamp is in manual on mode even though it's actually in the middle position (open door on mode).

And the diagram also shows in middle position #2 square is blank. If its shorted to 1 it will complete the circuit turning the light on.

If you can bend #2 tab so it does not touch 1 then it should be fine.

 

if i bent #2, so that it does not short 1', then the light will never come on, even if the door is open.
There has to be some switching/relay, that completes the circuit (grounds 1'), when the door is opened, and opens the circuit, when the door is closed.
thats is what i need to find out.

 

Anyone with 01 TL?
Can you confirm, if the pin that connects 1, is only shorted to ground when any of the door is opened, and opens the ground when all the doors are closed.

 

No because 1and 4 is connected and 3 goes to door swith. When door is open the circuit is complete... light on. Middle position.

Or the opposite depends which side is the ground.

 

ok.
so in that case, 3 should not have power all the time.
there should be 12V at #3 only when the door is open.
if the door is closed, then there is be no power at the 2 pin connector.

 

the table and the drawing does not match.
when you move the switch to middle position, the left 2 pins are shorted. As per the drawing, it means 1' and 2. but the table shows 1' and 4.
Do you agree?

 

Also as per the table, it shows 4 and 3 on either side of the bulb. But as per the drawing it shows 3 and 2 on either side of the bulb. 4 is just connected to a bolt on the roof.

 

Do any of you still own a 2001 tl?
We need to do a simple test.
With the switch in OFF position.
All doors closed.
Check voltage between 3 and 1' and 3 and 4.
Door open.
Check voltage between 3 and 1' and 3 and 4.

 

I didn't think it would require this, but I think the only way you're going to get any further with the diagnosis is to test the circuit under load. The load is the bulb, and you should check voltage at the two connectors with your meter negative connected to a known good ground. If I still remember correctly, if the doors are closed, the bulb is on dim with the overhead switch in the "door" position.
I still suspect the problem is on the ground side because of the odd 3 and 6 volt readings you've come up with. It's really unlikely that the switch is capable of this, especially consistently. The power side is wire and a fuse, which is also unlikely to do anything except 0 or 12v. Anyway, with the bulb in, and glowing, check the voltage at each end. It should be 12 volts on one end (terminal 3), and 0 volts on the other end (terminal 1). Since you have already said it glows dimly, and you have gotten 3, and 6 volt readings, I doubt this is the case. If you have 12v on the #3 terminal, I suspect you will have 3 or 6v on terminal 1.

 

At OFF the light is OFF, at middle the light is DIM, and at ON the light is BRIGHT. This does not change, if the door is open or closed.
All the tests done below are under load. #4 is a known good ground.


the only way to move forward is if someone with working light who can do the tests i have mentioned before.

 

Not really. If #4 is a good ground, then you know that #3 is at 12v as expected, and indicated by the wiring diagram. The voltage at #1 should be at 12v in the "door" position with the doors closed, and at 0v with any door open. The fact that you have 9v tells me that you've got a partial ground. Now you've got to trace that wire which terminates at the driver side multiplex.

 

Do any of you still own a 2001 tl?
We need to do a simple test.
With the switch in OFF position.
All doors closed.
Check voltage between 3 and 1' and 3 and 4.
Door open.
Check voltage between 3 and 1' and 3 and 4.

 

JIGS you are over thinking this.

First of all people shouldn't be testing electrical components with the power on unless they know what they are doing. That's how electronics are fry.

Your ceiling lamp only has 2 components, the ceiling lamp and passenger multiplex.

You should just do the "Ceiling light test" as noted in post #8. Follow the diagram test procedure only and ignore my comments. You are only testing for good continuity in the middle position. If any resistance is noted replace the ceiling light. If continuity is good, move on to the pass multiplex as noted below.




TL MULTIPLEX

 

Trying to measure the fuse length, with power on, stupidity... my mistake... over excitement.

Anyways, now to find the culprit, i have done several tests.
The problem with the continuity check, as per your post #8, is that the table does not match with the drawing.
As explained before; when you move the switch to middle position, the left 2 pins are shorted. As per the drawing, it means 1' and 2. but the table shows 1' and 4.
Also it shows 4 and 3 on either side of the bulb. But as per the drawing it shows 3 and 2 on either side of the bulb. 4 is just connected to a bolt on the roof, which is a positive ground. (the video also proves that)
Agree?

Now this multiplexer is a new thing? is it easy to reach to?

 

I'm sorry i don't see how it doesn't match.

All you're doing is removing the light from the car to test points 1 to 4, 1' to 4, 4 to 3, and 1 to 3, 1' to 3 for continuity. Anyone combination of those showing resistance means defective... replace or correct.

Note... tested with the switch in the middle position.

 

Thanks for being patience with me, and helping me out with this.
But i would defer from what you say.

Coming back to the same thing where i said the table does not match the drawing, here is a zoomed in photo of the drawing, where you can see that the pins connected to the bulb are 3 and 2 (blue and green) and not 3 and 4. You can see that in the middle position, the pin #4 (red) is not at all connected to anything. please see the switch on top (marked in purple), which shorts 1' and 2 when its in middle position. it is physically not possible for #4 pin to be connected to anything in the OFF and MIDDLE position..
so what i am saying is if the #2 and #4 are swapped on the drawing, the continuity checks out perfect, as that is physically possible, as it would put #3 and #4 on either side of the bulb.
I dont know a better way to explain this.
If you still do not agree with this, let me know exactly what you want me to do, and i will take a video if that and upload it here.

 

Ahh I see. The drawing is not to be taken literally. Its an illustration of where and what points to take the measurements. Also to label the points for reference.

If it was literal, there would be three drawings... one for each position.

On
Middle
Off

 

i have checked the switch physically and tested it as well.
its a mechanical switch, so it is literally the same as the drawing.
there is 'W' shaped copper contact bar, which makes contact with the pins, as you move the switch.
this is how it would look like in all the 3 positions.

 

Lol I see what you mean... 2 and 4 is jack up.

Ok then we'll use your pic below. Check for continuity between points 1 to 3 without power in middle position. If there is resistance replace the ceiling light. If continuity is good then check Pass multiplex. Don't know how hard it is to get to.