Toga

Thanks a lot for your suggestions!
the radio is working normally. All cables seem intact, protected by a black tape.In fact everything is working normally except the instrument lighting!
I investigated the ignition barrel too, verifying what was connected to the 12v in which position of the barrel. What I found is logic and working normally. On the electrical block diagram in the workshop manual, it appears that while the licence plate lighting works, all the line is correct until the relay. And the relay was swapped with no effect...
The only part I'm still not 100% sure about it, it's the potentiometer. For this part the dealer has the same answer as for the relay: never sell one in it's life! I'll tried by bridging 2 of the 3 connections, but nothing happened.

My question is the following, if one of you has time to loose and is willing to check the potentiometer connections, could he tell me if he gets 12V on one of them and under which conditions?

Summer's mystery

Warpig

I will try to take a look at mine this weekend with my meter. And report back.

I will also take a look at the wiring diagram but my car is a 95 and the wiring may be slightly different.

I will see if I can come up with a troubleshooting sequence for you. gonna depend on the diagram and how much disassembly is involved to make measurements.



Nick

RollingArt

Instrument panel lighting went out on my 986 Boxster.

Headlight switch was the culprit. They sell a ton of those!



Phil

Toga

Thanks Nick, very kind of you!

Thanks Phil. I checked mine, and it gives power to the connections it has to... so I don't believe it is the cause.

Here is the block diagram and in red where I checked positively a 12V input.

RollingArt

Looks like you checked power from light switch to tail lights, but what about to instrument cluster?

Think what I did was check wiring diagram to see which post on the switch feeds the instruments, and then put 12v to that post manually. If you do this and the cluster lights come on, that verifies the switch as the problem.



Phil

Toga

Thanks for your input Phil! So this is what I did:

I checked that post n°30 on the switch is connected to the pole n°58 while I turn the light switch on (position light). That allows 12V to reach the relay at pole 58. Working good.

On the relay socket I then bridged the pole 58 with pole P1. I measured 12v at the pole N°1 at the potentiometer plug. I connect the potentiometer on its plug, and on the relay position I measure 12v at P2 and P3. So the 12V find it's way back to the relay.

I verified again the relay: between poles 2 & 3 I read 44.2 KOhms. While I measure between 1&3 or 1&2 I read a value varying continuously from 0 to 44.2 while I turn the potentiometer button. I assume this is good.

On the relay socket, pole 31 is GROUND. verified and found ok

Then there is one pole left: n° 58d.
I bridged 58 with 58d and "pouf" the fuse burns... That's may be normal may be not... I don't know

The 58d goes to a connector we see on N3 on the block diagram... I'm trying to find it on my car...

Again, I'm no electrician, so if somebody reads something wrong in my conclusions or measurements please tell me

RollingArt

Maybe something is wrong with the instrument cluster?

Have you tried back-feeding the cluster with 12v to see if the lighting itself is ok?

Is there a small fuse on the back of the cluster itself that could be bad?



Phil

Toga

No I didn't feed directly one of the instruments. The fact is that I don't know where to feed, and avoid any mistake I chose not to do it. But the 58d is not logic to me. When I test the continuity between 58 and 58d, my meter beeps, which means they're connected?!?! Without the relay I don't understand this...
Concerning a fuse for the cluster, I removed all the instruments and didn't see any, nor on the diagram.

Well this is becoming difficult. I'll try to visit a specialist in car electricity, and see what he thinks.
I'll keep you informed

Toga

Hi all,

it's very hot here those days! around 35°C (95F°)! So I felt comfortable to stay in the freshness of my garage taking my time to figure out what was wrong with that lighting, and I solved it

I started by disconnecting all sources with were suppose (according to the different block diagrams) to be connected to the 58d on the relay. Then I reconnected them one by one. They were illuminated until I connected the ashtray light! I looked a bit further, and this is where I took the illumination signal for the night switching on the Becker Traffic pro... I then disconnected that wire, and recovered the ashtray lighting too.
Don't ask me why!! I don't understand anything, but the is fact that disconnecting the becker connection solved the problem

In the search process, I also took a closer look to the relay which in fact doesn't look just like a "simple" relay. Here's a pic of the inside:



Thanks to all for your inputs.

Warpig

Cool. Glad you got it worked out. I wanted to dig into mine last weekend (over the 4th) but didn't have time due to my sister & niece flying in from Phoenix, AZ. for the weekend. I only get to see them once or twice a year.

From how the thread was going I was fully expecting it to be the "Relay" as it sounded like everything was good to there. But you swapping it with another one blew my theory. Sounds like your Becker lead on 58d was loading down the circuit. With a standard relay that would not make sense. With a standard relay while loading down a circuit you would be very likely to pop a fuse. You popping open that R24 "Relay" and exposing that it really is NOT a relay at all but a small circuit jammed inside a relay case explains why there was no fuses popping due to the load down condition.

Great makes a little more sense now. Never seen a "Relay" like that before. Good job in tracking it down. Glad you got it worked out.

Nick

ToreB

We've got several of these small electronic units in our cars, many of them "disguised" as relays. Toga's picture reveal a simple PWM regulator design based on the ST electronics L9611 and a MOS transistor. Thanks for the information!

Your problem with the connection to the Becker head unit may be due to a wrongly placed illumination wire in the head unit harness? Is it really connected to connector A, pin 6?
Regards,
Tore

Toga

Thanks Tore. Yes the connection on the radio was ok and worked for years. Making this even harder to understand.
What mean PWM and MOS?

ToreB

An internal fault in the head unit must be the culprit then. Glad you found out.

Pulse Width Modulation is a method for easy power regulation, often used for regulating electric motor speed or light intensity.
Metal-oxide semiconductors are often used as the switching element in PWM applications reducing loss and heat.
Cheers,
Tore

Toga

Ouch! I confirm Electronic is like chinese to me. But it seems to be your branch Tore! thanks for your inputs.

Cannot resist to give my post an "Einstein level" :

TRM

Toga. I have the same problem. Everything works but the instrument lights are not illuminated....so if I understand correctly you identified the culprit as a blown R24 Relay due to an installation step with the Becker?

And then there is the ashtray light. I cut mine out a little while ago to make room for something special in the ashtray assembly. My dash lights might have failed after that but I don't recall directly since I don't drive the car much. But in the act of troubleshooting this issue I reconnected the wires, but it had no effect on the circuit.

I wonder if I somehow damaged the R24 Relay?